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Cycles: Add more scattering phase functions

Browse Source 
Previously, Cycles only supported the Henyey-Greenstein phase function for volume scattering.
While HG is flexible and works for a wide range of effects, sometimes a more physically accurate
phase function may be needed for realism.

Therefore, this adds three new phase functions to the code:
Rayleigh: For particles with a size below the wavelength of light, mostly athmospheric scattering.
Fournier-Forand: For realistic underwater scattering.
Draine: Fairly specific on its own (mostly for interstellar dust), but useful for the next entry.
Mie: Approximates Mie scattering in water droplets using a mix of Draine and HG phase functions.

These phase functions can be combined using Mix nodes as usual.

Co-authored-by: Lukas Stockner <lukas@lukasstockner.de>
Pull Request: https://projects.blender.org/blender/blender/pulls/123532
This commit is contained in:
Alexandre Cardaillac
2024-10-02 11:05:28 +02:00
committed by Lukas Stockner
parent db490e90fe
commit 0315eae536
27 changed files with 1027 additions and 172 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
intern/cycles/blender/shader.cpp
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@@ -721,7 +721,26 @@ static ShaderNode *add_node(Scene *scene,
node = ao;
}
else if (b_node.is_a(&RNA_ShaderNodeVolumeScatter)) {
node = graph->create_node<ScatterVolumeNode>();
BL::ShaderNodeVolumeScatter b_scatter_node(b_node);
ScatterVolumeNode *scatter = graph->create_node<ScatterVolumeNode>();
switch (b_scatter_node.phase()) {
case BL::ShaderNodeVolumeScatter::phase_HENYEY_GREENSTEIN:
scatter->set_phase(CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID);
break;
case BL::ShaderNodeVolumeScatter::phase_FOURNIER_FORAND:
scatter->set_phase(CLOSURE_VOLUME_FOURNIER_FORAND_ID);
break;
case BL::ShaderNodeVolumeScatter::phase_DRAINE:
scatter->set_phase(CLOSURE_VOLUME_DRAINE_ID);
break;
case BL::ShaderNodeVolumeScatter::phase_RAYLEIGH:
scatter->set_phase(CLOSURE_VOLUME_RAYLEIGH_ID);
break;
case BL::ShaderNodeVolumeScatter::phase_MIE:
scatter->set_phase(CLOSURE_VOLUME_MIE_ID);
break;
}
node = scatter;
}
else if (b_node.is_a(&RNA_ShaderNodeVolumeAbsorption)) {
node = graph->create_node<AbsorptionVolumeNode>();

5
intern/cycles/kernel/CMakeLists.txt
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@@ -161,6 +161,11 @@ set(SRC_KERNEL_CLOSURE_HEADERS
closure/bssrdf.h
closure/emissive.h
closure/volume.h
closure/volume_util.h
closure/volume_henyey_greenstein.h
closure/volume_rayleigh.h
closure/volume_fournier_forand.h
closure/volume_draine.h
closure/bsdf_principled_hair_chiang.h
closure/bsdf_principled_hair_huang.h
)

186
intern/cycles/kernel/closure/volume.h
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@@ -4,6 +4,13 @@
#pragma once
#include "kernel/closure/volume_util.h"
#include "kernel/closure/volume_draine.h"
#include "kernel/closure/volume_fournier_forand.h"
#include "kernel/closure/volume_henyey_greenstein.h"
#include "kernel/closure/volume_rayleigh.h"
CCL_NAMESPACE_BEGIN
/* VOLUME EXTINCTION */
@@ -19,110 +26,27 @@ ccl_device void volume_extinction_setup(ccl_private ShaderData *sd, Spectrum wei
}
}
/* HENYEY-GREENSTEIN CLOSURE */
typedef struct HenyeyGreensteinVolume {
SHADER_CLOSURE_BASE;
float g;
} HenyeyGreensteinVolume;
static_assert(sizeof(ShaderClosure) >= sizeof(HenyeyGreensteinVolume),
"HenyeyGreensteinVolume is too large!");
/* Given cosine between rays, return probability density that a photon bounces
* to that direction. The g parameter controls how different it is from the
* uniform sphere. g=0 uniform diffuse-like, g=1 close to sharp single ray. */
ccl_device float single_peaked_henyey_greenstein(float cos_theta, float g)
{
return ((1.0f - g * g) / safe_powf(1.0f + g * g - 2.0f * g * cos_theta, 1.5f)) *
(M_1_PI_F * 0.25f);
};
ccl_device int volume_henyey_greenstein_setup(ccl_private HenyeyGreensteinVolume *volume)
{
volume->type = CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID;
/* clamp anisotropy to avoid delta function */
volume->g = signf(volume->g) * min(fabsf(volume->g), 1.0f - 1e-3f);
return SD_SCATTER;
}
ccl_device Spectrum volume_henyey_greenstein_eval_phase(ccl_private const ShaderVolumeClosure *svc,
const float3 wi,
float3 wo,
ccl_private float *pdf)
{
float g = svc->g;
/* note that wi points towards the viewer */
if (fabsf(g) < 1e-3f) {
*pdf = M_1_PI_F * 0.25f;
}
else {
float cos_theta = dot(-wi, wo);
*pdf = single_peaked_henyey_greenstein(cos_theta, g);
}
return make_spectrum(*pdf);
}
ccl_device float3 henyey_greenstrein_sample(float3 D, float g, float2 rand, ccl_private float *pdf)
{
/* match pdf for small g */
float cos_theta;
bool isotropic = fabsf(g) < 1e-3f;
if (isotropic) {
cos_theta = (1.0f - 2.0f * rand.x);
if (pdf) {
*pdf = M_1_PI_F * 0.25f;
}
}
else {
float k = (1.0f - g * g) / (1.0f - g + 2.0f * g * rand.x);
cos_theta = (1.0f + g * g - k * k) / (2.0f * g);
if (pdf) {
*pdf = single_peaked_henyey_greenstein(cos_theta, g);
}
}
float sin_theta = sin_from_cos(cos_theta);
float phi = M_2PI_F * rand.y;
float3 dir = make_float3(sin_theta * cosf(phi), sin_theta * sinf(phi), cos_theta);
float3 T, B;
make_orthonormals(D, &T, &B);
dir = dir.x * T + dir.y * B + dir.z * D;
return dir;
}
ccl_device int volume_henyey_greenstein_sample(ccl_private const ShaderVolumeClosure *svc,
float3 wi,
float2 rand,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf)
{
float g = svc->g;
/* note that wi points towards the viewer and so is used negated */
*wo = henyey_greenstrein_sample(-wi, g, rand, pdf);
*eval = make_spectrum(*pdf); /* perfect importance sampling */
return LABEL_VOLUME_SCATTER;
}
/* VOLUME CLOSURE */
/* VOLUME SCATTERING */
ccl_device Spectrum volume_phase_eval(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float3 wo,
ccl_private float *pdf)
{
return volume_henyey_greenstein_eval_phase(svc, sd->wi, wo, pdf);
switch (svc->type) {
case CLOSURE_VOLUME_FOURNIER_FORAND_ID:
return volume_fournier_forand_eval(sd, svc, wo, pdf);
case CLOSURE_VOLUME_RAYLEIGH_ID:
return volume_rayleigh_eval(sd, wo, pdf);
case CLOSURE_VOLUME_DRAINE_ID:
return volume_draine_eval(sd, svc, wo, pdf);
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
return volume_henyey_greenstein_eval(sd, svc, wo, pdf);
default:
kernel_assert(false);
*pdf = 0.0f;
return zero_spectrum();
}
}
ccl_device int volume_phase_sample(ccl_private const ShaderData *sd,
@@ -132,7 +56,71 @@ ccl_device int volume_phase_sample(ccl_private const ShaderData *sd,
ccl_private float3 *wo,
ccl_private float *pdf)
{
return volume_henyey_greenstein_sample(svc, sd->wi, rand, eval, wo, pdf);
switch (svc->type) {
case CLOSURE_VOLUME_FOURNIER_FORAND_ID:
return volume_fournier_forand_sample(sd, svc, rand, eval, wo, pdf);
case CLOSURE_VOLUME_RAYLEIGH_ID:
return volume_rayleigh_sample(sd, rand, eval, wo, pdf);
case CLOSURE_VOLUME_DRAINE_ID:
return volume_draine_sample(sd, svc, rand, eval, wo, pdf);
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
return volume_henyey_greenstein_sample(sd, svc, rand, eval, wo, pdf);
default:
kernel_assert(false);
*pdf = 0.0f;
return 0;
}
}
ccl_device bool volume_phase_equal(ccl_private const ShaderClosure *c1,
ccl_private const ShaderClosure *c2)
{
if (c1->type != c2->type) {
return false;
}
switch (c1->type) {
case CLOSURE_VOLUME_FOURNIER_FORAND_ID: {
ccl_private FournierForandVolume *v1 = (ccl_private FournierForandVolume *)c1;
ccl_private FournierForandVolume *v2 = (ccl_private FournierForandVolume *)c2;
return v1->c1 == v2->c1 && v1->c2 == v2->c2 && v1->c3 == v2->c3;
}
case CLOSURE_VOLUME_RAYLEIGH_ID:
return true;
case CLOSURE_VOLUME_DRAINE_ID: {
ccl_private DraineVolume *v1 = (ccl_private DraineVolume *)c1;
ccl_private DraineVolume *v2 = (ccl_private DraineVolume *)c2;
return v1->g == v2->g && v1->alpha == v2->alpha;
}
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID: {
ccl_private HenyeyGreensteinVolume *v1 = (ccl_private HenyeyGreensteinVolume *)c1;
ccl_private HenyeyGreensteinVolume *v2 = (ccl_private HenyeyGreensteinVolume *)c2;
return v1->g == v2->g;
}
default:
return false;
}
return false;
}
/* Approximate phase functions as Henyey-Greenstein for volume guiding.
* TODO: This is not ideal, we should use RIS guiding for non-HG phase functions. */
ccl_device float volume_phase_get_g(ccl_private const ShaderVolumeClosure *svc)
{
switch (svc->type) {
case CLOSURE_VOLUME_FOURNIER_FORAND_ID:
/* TODO */
return 1.0f;
case CLOSURE_VOLUME_RAYLEIGH_ID:
/* Approximate as isotropic */
return 0.0f;
case CLOSURE_VOLUME_DRAINE_ID:
/* Approximate as HG, TODO */
return ((ccl_private DraineVolume *)svc)->g;
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
return ((ccl_private HenyeyGreensteinVolume *)svc)->g;
default:
return 0.0f;
}
}
/* Volume sampling utilities. */

60
intern/cycles/kernel/closure/volume_draine.h Normal file
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@@ -0,0 +1,60 @@
/* SPDX-FileCopyrightText: 2011-2024 Blender Foundation
*
* SPDX-License-Identifier: Apache-2.0 */
#pragma once
#include "kernel/closure/volume_util.h"
CCL_NAMESPACE_BEGIN
/* DRAINE CLOSURE */
typedef struct DraineVolume {
SHADER_CLOSURE_VOLUME_BASE;
float g;
float alpha;
} DraineVolume;
static_assert(sizeof(ShaderVolumeClosure) >= sizeof(DraineVolume), "DraineVolume is too large!");
ccl_device int volume_draine_setup(ccl_private DraineVolume *volume)
{
volume->type = CLOSURE_VOLUME_DRAINE_ID;
/* clamp anisotropy */
volume->g = signf(volume->g) * min(fabsf(volume->g), 1.0f - 1e-3f);
return SD_SCATTER;
}
ccl_device Spectrum volume_draine_eval(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float3 wo,
ccl_private float *pdf)
{
ccl_private const DraineVolume *volume = (ccl_private const DraineVolume *)svc;
/* note that wi points towards the viewer */
float cos_theta = dot(-sd->wi, wo);
*pdf = phase_draine(cos_theta, volume->g, volume->alpha);
return make_spectrum(*pdf);
}
ccl_device int volume_draine_sample(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float2 rand,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf)
{
ccl_private const DraineVolume *volume = (ccl_private const DraineVolume *)svc;
/* note that wi points towards the viewer and so is used negated */
*wo = phase_draine_sample(-sd->wi, volume->g, volume->alpha, rand, pdf);
*eval = make_spectrum(*pdf); /* perfect importance sampling */
return LABEL_VOLUME_SCATTER;
}
CCL_NAMESPACE_END

71
intern/cycles/kernel/closure/volume_fournier_forand.h Normal file
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@@ -0,0 +1,71 @@
/* SPDX-FileCopyrightText: 2011-2024 Blender Foundation
*
* SPDX-License-Identifier: Apache-2.0 */
#pragma once
#include "kernel/closure/volume_util.h"
CCL_NAMESPACE_BEGIN
/* FOURNIER-FORAND CLOSURE */
typedef struct FournierForandVolume {
SHADER_CLOSURE_VOLUME_BASE;
/* Precomputed coefficients, based on B and IOR */
float c1, c2, c3;
} FournierForandVolume;
static_assert(sizeof(ShaderVolumeClosure) >= sizeof(FournierForandVolume),
"FournierForandVolume is too large!");
ccl_device int volume_fournier_forand_setup(ccl_private FournierForandVolume *volume,
float B,
float IOR)
{
volume->type = CLOSURE_VOLUME_FOURNIER_FORAND_ID;
/* clamp backscatter fraction to avoid delta function */
B = min(fabsf(B), 0.5f - 1e-3f);
IOR = max(IOR, 1.0f + 1e-3f);
float3 coeffs = phase_fournier_forand_coeffs(B, IOR);
volume->c1 = coeffs.x;
volume->c2 = coeffs.y;
volume->c3 = coeffs.z;
return SD_SCATTER;
}
ccl_device Spectrum volume_fournier_forand_eval(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float3 wo,
ccl_private float *pdf)
{
ccl_private const FournierForandVolume *volume = (ccl_private const FournierForandVolume *)svc;
const float3 coeffs = make_float3(volume->c1, volume->c2, volume->c3);
/* note that wi points towards the viewer */
float cos_theta = dot(-sd->wi, wo);
*pdf = phase_fournier_forand(cos_theta, coeffs);
return make_spectrum(*pdf);
}
ccl_device int volume_fournier_forand_sample(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float2 rand,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf)
{
ccl_private const FournierForandVolume *volume = (ccl_private const FournierForandVolume *)svc;
const float3 coeffs = make_float3(volume->c1, volume->c2, volume->c3);
/* note that wi points towards the viewer and so is used negated */
*wo = phase_fournier_forand_sample(-sd->wi, coeffs, rand, pdf);
*eval = make_spectrum(*pdf); /* perfect importance sampling */
return LABEL_VOLUME_SCATTER;
}
CCL_NAMESPACE_END

62
intern/cycles/kernel/closure/volume_henyey_greenstein.h Normal file
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@@ -0,0 +1,62 @@
/* SPDX-FileCopyrightText: 2011-2024 Blender Foundation
*
* SPDX-License-Identifier: Apache-2.0 */
#pragma once
#include "kernel/closure/volume_util.h"
CCL_NAMESPACE_BEGIN
/* HENYEY-GREENSTEIN CLOSURE */
typedef struct HenyeyGreensteinVolume {
SHADER_CLOSURE_VOLUME_BASE;
float g;
} HenyeyGreensteinVolume;
static_assert(sizeof(ShaderVolumeClosure) >= sizeof(HenyeyGreensteinVolume),
"HenyeyGreensteinVolume is too large!");
ccl_device int volume_henyey_greenstein_setup(ccl_private HenyeyGreensteinVolume *volume)
{
volume->type = CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID;
/* clamp anisotropy to avoid delta function */
volume->g = signf(volume->g) * min(fabsf(volume->g), 1.0f - 1e-3f);
return SD_SCATTER;
}
ccl_device Spectrum volume_henyey_greenstein_eval(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float3 wo,
ccl_private float *pdf)
{
ccl_private const HenyeyGreensteinVolume *volume = (ccl_private const HenyeyGreensteinVolume *)
svc;
/* note that wi points towards the viewer */
float cos_theta = dot(-sd->wi, wo);
*pdf = phase_henyey_greenstein(cos_theta, volume->g);
return make_spectrum(*pdf);
}
ccl_device int volume_henyey_greenstein_sample(ccl_private const ShaderData *sd,
ccl_private const ShaderVolumeClosure *svc,
float2 rand,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf)
{
ccl_private const HenyeyGreensteinVolume *volume = (ccl_private const HenyeyGreensteinVolume *)
svc;
/* note that wi points towards the viewer and so is used negated */
*wo = phase_henyey_greenstein_sample(-sd->wi, volume->g, rand, pdf);
*eval = make_spectrum(*pdf); /* perfect importance sampling */
return LABEL_VOLUME_SCATTER;
}
CCL_NAMESPACE_END

49
intern/cycles/kernel/closure/volume_rayleigh.h Normal file
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@@ -0,0 +1,49 @@
/* SPDX-FileCopyrightText: 2011-2024 Blender Foundation
*
* SPDX-License-Identifier: Apache-2.0 */
#pragma once
#include "kernel/closure/volume_util.h"
CCL_NAMESPACE_BEGIN
/* RAYLEIGH CLOSURE */
typedef struct RayleighVolume {
SHADER_CLOSURE_VOLUME_BASE;
} RayleighVolume;
static_assert(sizeof(ShaderVolumeClosure) >= sizeof(RayleighVolume),
"RayleighVolume is too large!");
ccl_device int volume_rayleigh_setup(ccl_private RayleighVolume *volume)
{
volume->type = CLOSURE_VOLUME_RAYLEIGH_ID;
return SD_SCATTER;
}
ccl_device Spectrum volume_rayleigh_eval(ccl_private const ShaderData *sd,
float3 wo,
ccl_private float *pdf)
{
/* note that wi points towards the viewer */
float cos_theta = dot(-sd->wi, wo);
*pdf = phase_rayleigh(cos_theta);
return make_spectrum(*pdf);
}
ccl_device int volume_rayleigh_sample(ccl_private const ShaderData *sd,
float2 rand,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf)
{
/* note that wi points towards the viewer and so is used negated */
*wo = phase_rayleigh_sample(-sd->wi, rand, pdf);
*eval = make_spectrum(*pdf); /* perfect importance sampling */
return LABEL_VOLUME_SCATTER;
}
CCL_NAMESPACE_END

238
intern/cycles/kernel/closure/volume_util.h Normal file
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@@ -0,0 +1,238 @@
/* SPDX-FileCopyrightText: 2011-2024 Blender Foundation
*
* SPDX-License-Identifier: Apache-2.0 */
#pragma once
CCL_NAMESPACE_BEGIN
/* Given a random number, sample a direction that makes an angle of theta with direction D. */
ccl_device float3 phase_sample_direction(float3 D, float cos_theta, float rand)
{
float sin_theta = sin_from_cos(cos_theta);
float phi = M_2PI_F * rand;
float3 dir = make_float3(sin_theta * cosf(phi), sin_theta * sinf(phi), cos_theta);
float3 T, B;
make_orthonormals(D, &T, &B);
dir = dir.x * T + dir.y * B + dir.z * D;
return dir;
}
/* Given cosine between rays, return probability density that a photon bounces
* to that direction. The g parameter controls how different it is from the
* uniform sphere. g=0 uniform diffuse-like, g=1 close to sharp single ray. */
ccl_device float phase_henyey_greenstein(float cos_theta, float g)
{
if (fabsf(g) < 1e-3f) {
return M_1_4PI_F;
}
const float fac = 1 + g * (g - 2 * cos_theta);
return (1 - sqr(g)) / (M_4PI_F * fac * safe_sqrtf(fac));
}
ccl_device float3 phase_henyey_greenstein_sample(float3 D,
float g,
float2 rand,
ccl_private float *pdf)
{
float cos_theta = 1 - 2 * rand.x;
if (fabsf(g) >= 1e-3f) {
const float k = (1 - sqr(g)) / (1 - g * cos_theta);
cos_theta = (1 + sqr(g) - sqr(k)) / (2 * g);
}
*pdf = phase_henyey_greenstein(cos_theta, g);
return phase_sample_direction(D, cos_theta, rand.y);
}
/* Given cosine between rays, return probability density that a photon bounces to that direction
* according to the constant Rayleigh phase function.
* See https://doi.org/10.1364/JOSAA.28.002436 for details. */
ccl_device float phase_rayleigh(float cos_theta)
{
return (0.1875f * M_1_PI_F) * (1.0f + sqr(cos_theta));
}
ccl_device float3 phase_rayleigh_sample(float3 D, float2 rand, ccl_private float *pdf)
{
const float a = 2 - 4 * rand.x;
/* Metal doesn't have cbrtf, but since we compute u - 1/u anyways, we can just as well
* use the inverse cube root for which there is a simple Quake-style fast implementation.*/
const float inv_u = -fast_inv_cbrtf(sqrtf(1 + sqr(a)) - a);
const float cos_theta = 1 / inv_u - inv_u;
*pdf = phase_rayleigh(cos_theta);
return phase_sample_direction(D, cos_theta, rand.y);
}
/* Given cosine between rays, return probability density that a photon bounces to that direction
* according to the Draine phase function. This is a generalisation of the Henyey-Greenstein
* function which bridges the cases of HG and Rayleigh scattering. The parameter g mainly controls
* the first moment <cos theta>, and alpha the second moment <cos2 theta> of the exact phase
* function. alpha=0 reduces to HG function, g=0, alpha=1 reduces to Rayleigh function, alpha=1
* reduces to Cornette-Shanks function.
* See https://doi.org/10.1086/379118 for details. */
ccl_device float phase_draine(float cos_theta, float g, float alpha)
{
/* Check special cases. */
if (fabsf(g) < 1e-3f && alpha > 0.999f) {
return phase_rayleigh(cos_theta);
}
else if (fabsf(alpha) < 1e-3f) {
return phase_henyey_greenstein(cos_theta, g);
}
const float g2 = sqr(g);
const float fac = 1 + g2 - 2 * g * cos_theta;
return ((1 - g2) * (1 + alpha * sqr(cos_theta))) /
((1 + (alpha * (1 + 2 * g2)) * (1 / 3.0f)) * M_4PI_F * fac * sqrtf(fac));
}
/* Adapted from the hlsl code provided in https://research.nvidia.com/labs/rtr/approximate-mie/ */
ccl_device float phase_draine_sample_cos(float g, float alpha, float rand)
{
const float g2 = sqr(g), g3 = g * g2, g4 = sqr(g2), g6 = g2 * g4;
const float pgp1_2 = sqr(1 + g2);
const float T1a = alpha * (g4 - 1), T1a3 = sqr(T1a) * T1a;
const float T2 = -1296 * (g2 - 1) * (alpha - alpha * g2) * T1a * (4 * g2 + alpha * pgp1_2);
const float T9 = 2 + g2 + g3 * (1 + 2 * g2) * (2 * rand - 1);
const float T3 = 3 * g2 * (1 + g * (2 * rand - 1)) + alpha * T9;
const float T4a = 432 * T1a3 + T2 + 432 * (alpha * (1 - g2)) * sqr(T3);
const float T10 = alpha * (2 * g4 - g2 - g6);
const float T4b = 144 * T10, T4b3 = sqr(T4b) * T4b;
const float T4 = T4a + sqrtf(-4 * T4b3 + sqr(T4a));
const float inv_T4p3 = fast_inv_cbrtf(T4);
const float T8 = 48 * M_CBRT2_F * T10;
const float T6 = (2 * T1a + T8 * inv_T4p3 + 1 / (3 * M_CBRT2_F * inv_T4p3)) / (alpha * (1 - g2));
const float T5 = 6 * (1 + g2) + T6;
const float T7 = 6 * (1 + g2) - (8 * T3) / (alpha * (g2 - 1) * sqrtf(T5)) - T6;
return (1 + g2 - 0.25f * sqr(sqrtf(T7) - sqrtf(T5))) / (2 * g);
}
ccl_device float3
phase_draine_sample(float3 D, float g, float alpha, float2 rand, ccl_private float *pdf)
{
/* Check special cases. */
if (fabsf(g) < 1e-3f && alpha > 0.999f) {
return phase_rayleigh_sample(D, rand, pdf);
}
else if (fabsf(alpha) < 1e-3f) {
return phase_henyey_greenstein_sample(D, g, rand, pdf);
}
const float cos_theta = phase_draine_sample_cos(g, alpha, rand.x);
*pdf = phase_draine(cos_theta, g, alpha);
return phase_sample_direction(D, cos_theta, rand.y);
}
ccl_device float phase_fournier_forand_delta(float n, float sin_htheta_sqr)
{
float u = 4 * sin_htheta_sqr;
return u / (3 * sqr(n - 1));
}
ccl_device_inline float3 phase_fournier_forand_coeffs(float B, float IOR)
{
const float d90 = phase_fournier_forand_delta(IOR, 0.5f);
const float d180 = phase_fournier_forand_delta(IOR, 1.0f);
const float v = -logf(2 * B * (d90 - 1) + 1) / logf(d90);
return make_float3(IOR, v, (powf(d180, -v) - 1) / (d180 - 1));
}
/* Given cosine between rays, return probability density that a photon bounces to that direction
* according to the Fournier-Forand phase function. The n parameter is the particle index of
* refraction and controls how much of the light is refracted. B is the particle backscatter
* fraction, B = b_b / b.
* See https://doi.org/10.1117/12.366488 for details. */
ccl_device_inline float phase_fournier_forand_impl(
float cos_theta, float delta, float pow_delta_v, float v, float sin_htheta_sqr, float pf_coeff)
{
const float m_delta = 1 - delta, m_pow_delta_v = 1 - pow_delta_v;
float pf;
if (fabsf(m_delta) < 1e-3f) {
/* Special case (first-order Taylor expansion) to avoid singularity at delta near 1.0 */
pf = v * ((v - 1) - (v + 1) / sin_htheta_sqr) * (1 / (8 * M_PI_F));
pf += v * (v + 1) * m_delta * (2 * (v - 1) - (2 * v + 1) / sin_htheta_sqr) *
(1 / (24 * M_PI_F));
}
else {
pf = (v * m_delta - m_pow_delta_v + (delta * m_pow_delta_v - v * m_delta) / sin_htheta_sqr) /
(M_4PI_F * sqr(m_delta) * pow_delta_v);
}
pf += pf_coeff * (3 * sqr(cos_theta) - 1);
return pf;
}
ccl_device float phase_fournier_forand(float cos_theta, float3 coeffs)
{
if (fabsf(cos_theta) >= 1.0f) {
return 0.0f;
}
const float n = coeffs.x, v = coeffs.y;
const float pf_coeff = coeffs.z * (1.0f / (16.0f * M_PI_F));
const float sin_htheta_sqr = 0.5f * (1 - cos_theta); /* sin^2(theta / 2)*/
const float delta = phase_fournier_forand_delta(n, sin_htheta_sqr);
return phase_fournier_forand_impl(cos_theta, delta, powf(delta, v), v, sin_htheta_sqr, pf_coeff);
}
ccl_device float phase_fournier_forand_newton(float rand, float3 coeffs)
{
const float n = coeffs.x, v = coeffs.y;
const float cdf_coeff = coeffs.z * (1.0f / 8.0f);
const float pf_coeff = coeffs.z * (1.0f / (16.0f * M_PI_F));
float cos_theta = 0.64278760968f; /* Initial guess: 50 degrees */
for (int it = 0; it < 20; it++) {
const float sin_htheta_sqr = 0.5f * (1 - cos_theta); /* sin^2(theta / 2)*/
const float delta = phase_fournier_forand_delta(n, sin_htheta_sqr);
const float pow_delta_v = powf(delta, v);
const float m_delta = 1 - delta, m_pow_delta_v = 1 - pow_delta_v;
/* Evaluate CDF and phase functions */
float cdf;
if (fabsf(m_delta) < 1e-3f) {
/* Special case (first-order Taylor expansion) to avoid singularity at delta near 1.0 */
cdf = 1 + v * (1 - sin_htheta_sqr) * (1 - 0.5f * (v + 1) * m_delta);
}
else {
cdf = (1 - pow_delta_v * delta - m_pow_delta_v * sin_htheta_sqr) / (m_delta * pow_delta_v);
}
cdf += cdf_coeff * cos_theta * (1 - sqr(cos_theta));
const float pf = phase_fournier_forand_impl(
cos_theta, delta, pow_delta_v, v, sin_htheta_sqr, pf_coeff);
/* Perform Newton iteration step */
float new_cos_theta = cos_theta + M_1_2PI_F * (cdf - rand) / pf;
/* Don't step off past 1.0, approach the peak slowly */
if (new_cos_theta >= 1.0f) {
new_cos_theta = max(mix(cos_theta, 1.0f, 0.5f), 0.99f);
}
if (fabsf(cos_theta - new_cos_theta) < 1e-6f || new_cos_theta == 1.0f) {
return new_cos_theta;
}
cos_theta = new_cos_theta;
}
/* Reached iteration limit, so give up and use what we have. */
return cos_theta;
}
ccl_device float3 phase_fournier_forand_sample(float3 D,
float3 coeffs,
float2 rand,
ccl_private float *pdf)
{
float cos_theta = phase_fournier_forand_newton(rand.x, coeffs);
*pdf = phase_fournier_forand(cos_theta, coeffs);
return phase_sample_direction(D, cos_theta, rand.y);
}
CCL_NAMESPACE_END

4
intern/cycles/kernel/integrator/subsurface_random_walk.h
View File

@@ -315,11 +315,11 @@ ccl_device_inline bool subsurface_random_walk(KernelGlobals kg,
cos_theta = -cos_theta;
}
float3 newD = direction_from_cosine(N, cos_theta, rand_scatter.y);
hg_pdf = single_peaked_henyey_greenstein(dot(ray.D, newD), anisotropy);
hg_pdf = phase_henyey_greenstein(dot(ray.D, newD), anisotropy);
ray.D = newD;
}
else {
float3 newD = henyey_greenstrein_sample(ray.D, anisotropy, rand_scatter, &hg_pdf);
float3 newD = phase_henyey_greenstein_sample(ray.D, anisotropy, rand_scatter, &hg_pdf);
cos_theta = dot(newD, N);
ray.D = newD;
}

33
intern/cycles/kernel/integrator/volume_shader.h
View File

@@ -30,21 +30,13 @@ ccl_device_inline void volume_shader_merge_closures(ccl_private ShaderData *sd)
for (int i = 0; i < sd->num_closure; i++) {
ccl_private ShaderClosure *sci = &sd->closure[i];
if (sci->type != CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID) {
if (!CLOSURE_IS_VOLUME_SCATTER(sci->type)) {
continue;
}
for (int j = i + 1; j < sd->num_closure; j++) {
ccl_private ShaderClosure *scj = &sd->closure[j];
if (sci->type != scj->type) {
continue;
}
ccl_private const HenyeyGreensteinVolume *hgi = (ccl_private const HenyeyGreensteinVolume *)
sci;
ccl_private const HenyeyGreensteinVolume *hgj = (ccl_private const HenyeyGreensteinVolume *)
scj;
if (!(hgi->g == hgj->g)) {
if (!volume_phase_equal(sci, scj)) {
continue;
}
@@ -73,16 +65,10 @@ ccl_device_inline void volume_shader_copy_phases(ccl_private ShaderVolumePhases
for (int i = 0; i < sd->num_closure; i++) {
ccl_private const ShaderClosure *from_sc = &sd->closure[i];
ccl_private const HenyeyGreensteinVolume *from_hg =
(ccl_private const HenyeyGreensteinVolume *)from_sc;
if (from_sc->type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID) {
ccl_private ShaderVolumeClosure *to_sc = &phases->closure[phases->num_closure];
to_sc->weight = from_sc->weight;
to_sc->sample_weight = from_sc->sample_weight;
to_sc->g = from_hg->g;
phases->num_closure++;
if (CLOSURE_IS_VOLUME_SCATTER(from_sc->type)) {
/* ShaderVolumeClosure is a subset of ShaderClosure, so this is fine for all volume scatter
* closures. */
phases->closure[phases->num_closure++] = *((ccl_private const ShaderVolumeClosure *)from_sc);
if (phases->num_closure >= MAX_VOLUME_CLOSURE) {
break;
}
@@ -147,7 +133,8 @@ ccl_device_inline void volume_shader_prepare_guiding(KernelGlobals kg,
/* Init guiding for selected phase function. */
ccl_private const ShaderVolumeClosure *svc = &phases->closure[phase_id];
if (!guiding_phase_init(kg, state, P, D, svc->g, rand_phase_guiding)) {
const float phase_g = volume_phase_get_g(svc);
if (!guiding_phase_init(kg, state, P, D, phase_g, rand_phase_guiding)) {
state->guiding.use_volume_guiding = false;
return;
}
@@ -301,7 +288,7 @@ ccl_device int volume_shader_phase_guided_sample(KernelGlobals kg,
*unguided_phase_pdf = 0.0f;
float guide_pdf = 0.0f;
*sampled_roughness = 1.0f - fabsf(svc->g);
*sampled_roughness = 1.0f - fabsf(volume_phase_get_g(svc));
bsdf_eval_init(phase_eval, zero_spectrum());
@@ -355,7 +342,7 @@ ccl_device int volume_shader_phase_sample(KernelGlobals kg,
ccl_private float *pdf,
ccl_private float *sampled_roughness)
{
*sampled_roughness = 1.0f - fabsf(svc->g);
*sampled_roughness = 1.0f - fabsf(volume_phase_get_g(svc));
Spectrum eval = zero_spectrum();
*pdf = 0.0f;

58
intern/cycles/kernel/osl/closures_setup.h
View File

@@ -1086,4 +1086,62 @@ ccl_device void osl_closure_henyey_greenstein_setup(
sd->flag |= volume_henyey_greenstein_setup(volume);
}
ccl_device void osl_closure_fournier_forand_setup(
KernelGlobals kg,
ccl_private ShaderData *sd,
uint32_t path_flag,
float3 weight,
ccl_private const VolumeFournierForandClosure *closure,
float3 *layer_albedo)
{
volume_extinction_setup(sd, rgb_to_spectrum(weight));
ccl_private FournierForandVolume *volume = (ccl_private FournierForandVolume *)bsdf_alloc(
sd, sizeof(FournierForandVolume), rgb_to_spectrum(weight));
if (!volume) {
return;
}
sd->flag |= volume_fournier_forand_setup(volume, closure->B, closure->IOR);
}
ccl_device void osl_closure_draine_setup(KernelGlobals kg,
ccl_private ShaderData *sd,
uint32_t path_flag,
float3 weight,
ccl_private const VolumeDraineClosure *closure,
float3 *layer_albedo)
{
volume_extinction_setup(sd, rgb_to_spectrum(weight));
ccl_private DraineVolume *volume = (ccl_private DraineVolume *)bsdf_alloc(
sd, sizeof(DraineVolume), rgb_to_spectrum(weight));
if (!volume) {
return;
}
volume->g = closure->g;
volume->alpha = closure->alpha;
sd->flag |= volume_draine_setup(volume);
}
ccl_device void osl_closure_rayleigh_setup(KernelGlobals kg,
ccl_private ShaderData *sd,
uint32_t path_flag,
float3 weight,
ccl_private const VolumeRayleighClosure *closure,
float3 *layer_albedo)
{
volume_extinction_setup(sd, rgb_to_spectrum(weight));
ccl_private RayleighVolume *volume = (ccl_private RayleighVolume *)bsdf_alloc(
sd, sizeof(RayleighVolume), rgb_to_spectrum(weight));
if (!volume) {
return;
}
sd->flag |= volume_rayleigh_setup(volume);
}
CCL_NAMESPACE_END

13
intern/cycles/kernel/osl/closures_template.h
View File

@@ -223,6 +223,19 @@ OSL_CLOSURE_STRUCT_BEGIN(VolumeHenyeyGreenstein, henyey_greenstein)
OSL_CLOSURE_STRUCT_MEMBER(VolumeHenyeyGreenstein, FLOAT, float, g, NULL)
OSL_CLOSURE_STRUCT_END(VolumeHenyeyGreenstein, henyey_greenstein)
OSL_CLOSURE_STRUCT_BEGIN(VolumeFournierForand, fournier_forand)
OSL_CLOSURE_STRUCT_MEMBER(VolumeFournierForand, FLOAT, float, B, NULL)
OSL_CLOSURE_STRUCT_MEMBER(VolumeFournierForand, FLOAT, float, IOR, NULL)
OSL_CLOSURE_STRUCT_END(VolumeFournierForand, fournier_forand)
OSL_CLOSURE_STRUCT_BEGIN(VolumeDraine, draine)
OSL_CLOSURE_STRUCT_MEMBER(VolumeDraine, FLOAT, float, g, NULL)
OSL_CLOSURE_STRUCT_MEMBER(VolumeDraine, FLOAT, float, alpha, NULL)
OSL_CLOSURE_STRUCT_END(VolumeDraine, draine)
OSL_CLOSURE_STRUCT_BEGIN(VolumeRayleigh, rayleigh)
OSL_CLOSURE_STRUCT_END(VolumeRayleigh, rayleigh)
#undef OSL_CLOSURE_STRUCT_BEGIN
#undef OSL_CLOSURE_STRUCT_END
#undef OSL_CLOSURE_STRUCT_MEMBER

33
intern/cycles/kernel/osl/shaders/node_scatter_volume.osl
View File

@@ -4,10 +4,39 @@
#include "stdcycles.h"
shader node_scatter_volume(color Color = color(0.8, 0.8, 0.8),
shader node_scatter_volume(string phase = "Henyey-Greenstein",
color Color = color(0.8, 0.8, 0.8),
float Density = 1.0,
float Anisotropy = 0.0,
float IOR = 1.33,
float Backscatter = 0.1,
float Alpha = 0.5,
float Diameter = 20.0,
output closure color Volume = 0)
{
Volume = (Color * max(Density, 0.0)) * henyey_greenstein(Anisotropy);
closure color scatter = 0;
if (phase == "Fournier-Forand") {
scatter = fournier_forand(Backscatter, IOR);
}
else if (phase == "Draine") {
scatter = draine(Anisotropy, Alpha);
}
else if (phase == "Rayleigh") {
scatter = rayleigh();
}
else if (phase == "Mie") {
/* Approxmiation of Mie phase function for water droplets using a mix of Draine and H-G.
* See kernel/svm/closure.h for details. */
float d = max(Diameter, 2.0);
float aniso_hg = exp(-0.0990567 / (d - 1.67154));
float aniso_d = exp(-2.20679 / (d + 3.91029) - 0.428934);
float alpha = exp(3.62489 - 8.29288 / (d + 5.52825));
float mixture = exp(-0.599085 / (d - 0.641583) - 0.665888);
scatter = mix(henyey_greenstein(aniso_hg), draine(aniso_d, alpha), mixture);
}
else {
scatter = henyey_greenstein(Anisotropy);
}
Volume = (Color * max(Density, 0.0)) * scatter;
}

3
intern/cycles/kernel/osl/shaders/stdcycles.h
View File

@@ -61,6 +61,9 @@ closure color hair_huang(normal N,
// Volume
closure color henyey_greenstein(float g) BUILTIN;
closure color fournier_forand(float B, float IOR) BUILTIN;
closure color draine(float g, float alpha) BUILTIN;
closure color rayleigh() BUILTIN;
closure color absorption() BUILTIN;
// Ray Portal

81
intern/cycles/kernel/svm/closure.h
View File

@@ -1006,13 +1006,10 @@ ccl_device_noinline void svm_node_closure_volume(KernelGlobals kg,
return;
}
uint type, density_offset, anisotropy_offset;
uint mix_weight_offset;
svm_unpack_node_uchar4(node.y, &type, &density_offset, &anisotropy_offset, &mix_weight_offset);
uint type, density_offset, param1_offset, mix_weight_offset;
svm_unpack_node_uchar4(node.y, &type, &density_offset, &param1_offset, &mix_weight_offset);
float mix_weight = (stack_valid(mix_weight_offset) ? stack_load_float(stack, mix_weight_offset) :
1.0f);
if (mix_weight == 0.0f) {
return;
}
@@ -1031,16 +1028,70 @@ ccl_device_noinline void svm_node_closure_volume(KernelGlobals kg,
weight *= density;
/* Add closure for volume scattering. */
if (type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID) {
ccl_private HenyeyGreensteinVolume *volume = (ccl_private HenyeyGreensteinVolume *)bsdf_alloc(
sd, sizeof(HenyeyGreensteinVolume), weight);
if (volume) {
float anisotropy = (stack_valid(anisotropy_offset)) ?
stack_load_float(stack, anisotropy_offset) :
__uint_as_float(node.w);
volume->g = anisotropy; /* g */
sd->flag |= volume_henyey_greenstein_setup(volume);
if (CLOSURE_IS_VOLUME_SCATTER(type)) {
switch (type) {
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID: {
ccl_private HenyeyGreensteinVolume *volume = (ccl_private HenyeyGreensteinVolume *)
bsdf_alloc(sd, sizeof(HenyeyGreensteinVolume), weight);
if (volume) {
volume->g = stack_valid(param1_offset) ? stack_load_float(stack, param1_offset) :
__uint_as_float(node.w);
sd->flag |= volume_henyey_greenstein_setup(volume);
}
} break;
case CLOSURE_VOLUME_FOURNIER_FORAND_ID: {
ccl_private FournierForandVolume *volume = (ccl_private FournierForandVolume *)bsdf_alloc(
sd, sizeof(FournierForandVolume), weight);
if (volume) {
const float IOR = stack_load_float(stack, param1_offset);
const float B = stack_load_float(stack, node.w);
sd->flag |= volume_fournier_forand_setup(volume, B, IOR);
}
} break;
case CLOSURE_VOLUME_RAYLEIGH_ID: {
ccl_private RayleighVolume *volume = (ccl_private RayleighVolume *)bsdf_alloc(
sd, sizeof(RayleighVolume), weight);
if (volume) {
sd->flag |= volume_rayleigh_setup(volume);
}
break;
}
case CLOSURE_VOLUME_DRAINE_ID: {
ccl_private DraineVolume *volume = (ccl_private DraineVolume *)bsdf_alloc(
sd, sizeof(DraineVolume), weight);
if (volume) {
volume->g = stack_load_float(stack, param1_offset);
volume->alpha = stack_load_float(stack, node.w);
sd->flag |= volume_draine_setup(volume);
}
} break;
case CLOSURE_VOLUME_MIE_ID: {
/* We approximate the Mie phase function for water droplets using a mix of Draine and H-G
* following "An Approximate Mie Scattering Function for Fog and Cloud Rendering", Johannes
* Jendersie and Eugene d'Eon, https://research.nvidia.com/labs/rtr/approximate-mie.
*
* The numerical fit here (eq. 4-7 in the paper) is intended for 5<d<50.
* Generally, we try to allow exceeding the soft limits when reasonable. Here, the only
* real limit is that the values need to stay within -1<g<1, 0<a and 0<mixture<1.
* This results in the condition d > 1.67154, so we clamp it to 2 to be safe. */
const float d = max(2.0f,
stack_valid(param1_offset) ? stack_load_float(stack, param1_offset) :
__uint_as_float(node.w));
const float mixture = fast_expf(-0.599085f / (d - 0.641583f) - 0.665888f);
ccl_private HenyeyGreensteinVolume *hg = (ccl_private HenyeyGreensteinVolume *)bsdf_alloc(
sd, sizeof(HenyeyGreensteinVolume), weight * (1.0f - mixture));
if (hg) {
hg->g = fast_expf(-0.0990567f / (d - 1.67154f));
sd->flag |= volume_henyey_greenstein_setup(hg);
}
ccl_private DraineVolume *draine = (ccl_private DraineVolume *)bsdf_alloc(
sd, sizeof(DraineVolume), weight * mixture);
if (draine) {
draine->g = fast_expf(-2.20679f / (d + 3.91029f) - 0.428934f);
draine->alpha = fast_expf(3.62489f - 8.29288f / (d + 5.52825f));
sd->flag |= volume_draine_setup(draine);
}
} break;
}
}

13
intern/cycles/kernel/svm/types.h
View File

@@ -470,6 +470,10 @@ typedef enum ClosureType {
CLOSURE_VOLUME_ID,
CLOSURE_VOLUME_ABSORPTION_ID,
CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID,
CLOSURE_VOLUME_MIE_ID, /* virtual closure */
CLOSURE_VOLUME_FOURNIER_FORAND_ID,
CLOSURE_VOLUME_RAYLEIGH_ID,
CLOSURE_VOLUME_DRAINE_ID,
CLOSURE_BSDF_PRINCIPLED_ID,
@@ -502,12 +506,13 @@ typedef enum ClosureType {
(type != CLOSURE_NONE_ID && type <= CLOSURE_BSSRDF_RANDOM_WALK_SKIN_ID)
#define CLOSURE_IS_BSSRDF(type) \
(type >= CLOSURE_BSSRDF_BURLEY_ID && type <= CLOSURE_BSSRDF_RANDOM_WALK_SKIN_ID)
#define CLOSURE_IS_VOLUME(type) \
(type >= CLOSURE_VOLUME_ID && type <= CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
#define CLOSURE_IS_VOLUME_SCATTER(type) (type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
#define CLOSURE_IS_VOLUME(type) (type >= CLOSURE_VOLUME_ID && type <= CLOSURE_VOLUME_DRAINE_ID)
#define CLOSURE_IS_VOLUME_SCATTER(type) \
(type >= CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID && type <= CLOSURE_VOLUME_DRAINE_ID)
#define CLOSURE_IS_VOLUME_ABSORPTION(type) (type == CLOSURE_VOLUME_ABSORPTION_ID)
#define CLOSURE_IS_HOLDOUT(type) (type == CLOSURE_HOLDOUT_ID)
#define CLOSURE_IS_PHASE(type) (type == CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID)
#define CLOSURE_IS_PHASE(type) \
(type >= CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID && type <= CLOSURE_VOLUME_DRAINE_ID)
#define CLOSURE_IS_REFRACTION(type) \
(type >= CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID && \
type <= CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID)

21
intern/cycles/kernel/types.h
View File

@@ -977,6 +977,15 @@ typedef struct AttributeMap {
float sample_weight; \
float3 N
/* To save some space, volume closures (phase functions) don't store a normal.
* They are still allocated as ShaderClosures first, but get assigned to
* slots of type ShaderVolumeClosure later, so make sure to keep the layout
* in sync. */
#define SHADER_CLOSURE_VOLUME_BASE \
Spectrum weight; \
ClosureType type; \
float sample_weight
typedef struct ccl_align(16) ShaderClosure
{
SHADER_CLOSURE_BASE;
@@ -1221,12 +1230,18 @@ ShaderDataCausticsStorage;
/* Compact volume closures storage.
*
* Used for decoupled direct/indirect light closure storage. */
* Used for decoupled direct/indirect light closure storage.
*
* This shares its basic layout with SHADER_CLOSURE_VOLUME_BASE and ShaderClosure,
* just without the normal and with less space for closure-specific parameters.
* That way, we can just cast ShaderClosure* to ShaderVolumeClosure* and assign it.
*/
typedef struct ShaderVolumeClosure {
Spectrum weight;
ClosureType type;
float sample_weight;
float g;
/* Space for closure-specific parameters. */
float param[3];
} ShaderVolumeClosure;
typedef struct ShaderVolumePhases {

75
intern/cycles/scene/shader_nodes.cpp
View File

@@ -3400,7 +3400,10 @@ VolumeNode::VolumeNode(const NodeType *node_type) : ShaderNode(node_type)
closure = CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID;
}
void VolumeNode::compile(SVMCompiler &compiler, ShaderInput *param1, ShaderInput *param2)
void VolumeNode::compile(SVMCompiler &compiler,
ShaderInput *density,
ShaderInput *param1,
ShaderInput *param2)
{
ShaderInput *color_in = input("Color");
@@ -3411,19 +3414,32 @@ void VolumeNode::compile(SVMCompiler &compiler, ShaderInput *param1, ShaderInput
compiler.add_node(NODE_CLOSURE_SET_WEIGHT, color);
}
compiler.add_node(
NODE_CLOSURE_VOLUME,
compiler.encode_uchar4(closure,
(param1) ? compiler.stack_assign(param1) : SVM_STACK_INVALID,
(param2) ? compiler.stack_assign(param2) : SVM_STACK_INVALID,
compiler.closure_mix_weight_offset()),
__float_as_int((param1) ? get_float(param1->socket_type) : 0.0f),
__float_as_int((param2) ? get_float(param2->socket_type) : 0.0f));
/* Density and mix weight need to be stored the same way for all volume closures since there's
* a shortcut code path if we only need the extinction value. */
uint density_ofs = (density) ? compiler.stack_assign_if_linked(density) : SVM_STACK_INVALID;
uint mix_weight_ofs = compiler.closure_mix_weight_offset();
if (param2 == nullptr) {
/* More efficient packing if we don't need the second parameter. */
uint param1_ofs = (param1) ? compiler.stack_assign_if_linked(param1) : SVM_STACK_INVALID;
compiler.add_node(NODE_CLOSURE_VOLUME,
compiler.encode_uchar4(closure, density_ofs, param1_ofs, mix_weight_ofs),
__float_as_int((density) ? get_float(density->socket_type) : 0.0f),
__float_as_int((param1) ? get_float(param1->socket_type) : 0.0f));
}
else {
uint param1_ofs = (param1) ? compiler.stack_assign(param1) : SVM_STACK_INVALID;
uint param2_ofs = (param2) ? compiler.stack_assign(param2) : SVM_STACK_INVALID;
compiler.add_node(NODE_CLOSURE_VOLUME,
compiler.encode_uchar4(closure, density_ofs, param1_ofs, mix_weight_ofs),
__float_as_int((density) ? get_float(density->socket_type) : 0.0f),
param2_ofs);
}
}
void VolumeNode::compile(SVMCompiler &compiler)
{
compile(compiler, NULL, NULL);
compile(compiler, nullptr, nullptr, nullptr);
}
void VolumeNode::compile(OSLCompiler & /*compiler*/)
@@ -3453,7 +3469,7 @@ AbsorptionVolumeNode::AbsorptionVolumeNode() : VolumeNode(get_node_type())
void AbsorptionVolumeNode::compile(SVMCompiler &compiler)
{
VolumeNode::compile(compiler, input("Density"), NULL);
VolumeNode::compile(compiler, input("Density"));
}
void AbsorptionVolumeNode::compile(OSLCompiler &compiler)
@@ -3470,6 +3486,19 @@ NODE_DEFINE(ScatterVolumeNode)
SOCKET_IN_COLOR(color, "Color", make_float3(0.8f, 0.8f, 0.8f));
SOCKET_IN_FLOAT(density, "Density", 1.0f);
SOCKET_IN_FLOAT(anisotropy, "Anisotropy", 0.0f);
SOCKET_IN_FLOAT(IOR, "IOR", 1.33f);
SOCKET_IN_FLOAT(backscatter, "Backscatter", 0.1f);
SOCKET_IN_FLOAT(alpha, "Alpha", 0.5f);
SOCKET_IN_FLOAT(diameter, "Diameter", 20.0f);
static NodeEnum phase_enum;
phase_enum.insert("Henyey-Greenstein", CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID);
phase_enum.insert("Fournier-Forand", CLOSURE_VOLUME_FOURNIER_FORAND_ID);
phase_enum.insert("Draine", CLOSURE_VOLUME_DRAINE_ID);
phase_enum.insert("Rayleigh", CLOSURE_VOLUME_RAYLEIGH_ID);
phase_enum.insert("Mie", CLOSURE_VOLUME_MIE_ID);
SOCKET_ENUM(phase, "Phase", phase_enum, CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID);
SOCKET_IN_FLOAT(volume_mix_weight, "VolumeMixWeight", 0.0f, SocketType::SVM_INTERNAL);
SOCKET_OUT_CLOSURE(volume, "Volume");
@@ -3484,11 +3513,33 @@ ScatterVolumeNode::ScatterVolumeNode() : VolumeNode(get_node_type())
void ScatterVolumeNode::compile(SVMCompiler &compiler)
{
VolumeNode::compile(compiler, input("Density"), input("Anisotropy"));
closure = phase;
switch (phase) {
case CLOSURE_VOLUME_HENYEY_GREENSTEIN_ID:
VolumeNode::compile(compiler, input("Density"), input("Anisotropy"));
break;
case CLOSURE_VOLUME_FOURNIER_FORAND_ID:
VolumeNode::compile(compiler, input("Density"), input("IOR"), input("Backscatter"));
break;
case CLOSURE_VOLUME_RAYLEIGH_ID:
VolumeNode::compile(compiler, input("Density"));
break;
case CLOSURE_VOLUME_DRAINE_ID:
VolumeNode::compile(compiler, input("Density"), input("Anisotropy"), input("Alpha"));
break;
case CLOSURE_VOLUME_MIE_ID:
VolumeNode::compile(compiler, input("Density"), input("Diameter"));
break;
default:
assert(false);
break;
}
}
void ScatterVolumeNode::compile(OSLCompiler &compiler)
{
compiler.parameter(this, "phase");
compiler.add(this, "node_scatter_volume");
}

10
intern/cycles/scene/shader_nodes.h
View File

@@ -796,7 +796,10 @@ class VolumeNode : public ShaderNode {
VolumeNode(const NodeType *node_type);
SHADER_NODE_BASE_CLASS(VolumeNode)
void compile(SVMCompiler &compiler, ShaderInput *param1, ShaderInput *param2);
void compile(SVMCompiler &compiler,
ShaderInput *density,
ShaderInput *param1 = nullptr,
ShaderInput *param2 = nullptr);
virtual int get_feature()
{
return ShaderNode::get_feature() | KERNEL_FEATURE_NODE_VOLUME;
@@ -835,6 +838,11 @@ class ScatterVolumeNode : public VolumeNode {
SHADER_NODE_CLASS(ScatterVolumeNode)
NODE_SOCKET_API(float, anisotropy)
NODE_SOCKET_API(float, IOR)
NODE_SOCKET_API(float, backscatter)
NODE_SOCKET_API(float, alpha)
NODE_SOCKET_API(float, diameter)
NODE_SOCKET_API(ClosureType, phase)
};
class PrincipledVolumeNode : public VolumeNode {

6
intern/cycles/util/math.h
View File

@@ -49,6 +49,9 @@ CCL_NAMESPACE_BEGIN
#ifndef M_1_2PI_F
# define M_1_2PI_F (0.1591549430918953f) /* 1/(2*pi) */
#endif
#ifndef M_1_4PI_F
# define M_1_4PI_F (0.0795774715459476f) /* 1/(4*pi) */
#endif
#ifndef M_SQRT_PI_8_F
# define M_SQRT_PI_8_F (0.6266570686577501f) /* sqrt(pi/8) */
#endif
@@ -71,6 +74,9 @@ CCL_NAMESPACE_BEGIN
#ifndef M_SQRT2_F
# define M_SQRT2_F (1.4142135623730950f) /* sqrt(2) */
#endif
#ifndef M_CBRT2_F
# define M_CBRT2_F 1.2599210498948732f /* cbrt(2) */
#endif
#ifndef M_SQRT1_2F
# define M_SQRT1_2F 0.70710678118654752440f /* sqrt(1/2) */
#endif

13
intern/cycles/util/math_fast.h
View File

@@ -634,6 +634,19 @@ ccl_device_inline float fast_ierff(float x)
return p * x;
}
/* Fast inverse cube root for positive x, with two Newton iterations to improve accuracy. */
ccl_device_inline float fast_inv_cbrtf(float x)
{
util_assert(x >= 0.0f);
/* Constant is roughly cbrt(2^127), but tweaked a bit to balance the error across the entire
* range. The exact value is not critical. */
float y = __int_as_float(0x54a24242 - __float_as_int(x) / 3);
y = (2.0f / 3) * y + 1 / (3 * y * y * x);
y = (2.0f / 3) * y + 1 / (3 * y * y * x);
return y;
}
CCL_NAMESPACE_END
#endif /* __UTIL_FAST_MATH__ */

8
source/blender/editors/space_node/drawnode.cc
View File

@@ -445,6 +445,11 @@ static void node_buts_output_shader(uiLayout *layout, bContext * /*C*/, PointerR
uiItemR(layout, ptr, "target", DEFAULT_FLAGS, "", ICON_NONE);
}
static void node_shader_buts_scatter(uiLayout *layout, bContext * /*C*/, PointerRNA *ptr)
{
uiItemR(layout, ptr, "phase", DEFAULT_FLAGS, "", ICON_NONE);
}
/* only once called */
static void node_shader_set_butfunc(blender::bke::bNodeType *ntype)
{
@@ -501,6 +506,9 @@ static void node_shader_set_butfunc(blender::bke::bNodeType *ntype)
case SH_NODE_OUTPUT_WORLD:
ntype->draw_buttons = node_buts_output_shader;
break;
case SH_NODE_VOLUME_SCATTER:
ntype->draw_buttons = node_shader_buts_scatter;
break;
}
}

11
source/blender/gpu/shaders/material/gpu_shader_material_volume_scatter.glsl
View File

@@ -2,8 +2,15 @@
*
* SPDX-License-Identifier: GPL-2.0-or-later */
void node_volume_scatter(
vec4 color, float density, float anisotropy, float weight, out Closure result)
void node_volume_scatter(vec4 color,
float density,
float anisotropy,
float IOR,
float Backscatter,
float alpha,
float diameter,
float weight,
out Closure result)
{
color = max(color, vec4(0.0));
density = max(density, 0.0);

9
source/blender/makesdna/DNA_node_types.h
View File

@@ -2849,6 +2849,15 @@ enum {
SHD_POINTDENSITY_COLOR_VERTNOR = 2,
};
/* Scattering phase functions */
enum {
SHD_PHASE_HENYEY_GREENSTEIN = 0,
SHD_PHASE_FOURNIER_FORAND = 1,
SHD_PHASE_DRAINE = 2,
SHD_PHASE_RAYLEIGH = 3,
SHD_PHASE_MIE = 4,
};
/* Output shader node */
typedef enum NodeShaderOutputTarget {

42
source/blender/makesrna/intern/rna_nodetree.cc
View File

@@ -4476,6 +4476,37 @@ static const EnumPropertyItem prop_image_extension[] = {
{0, nullptr, 0, nullptr, nullptr},
};
static const EnumPropertyItem node_scatter_phase_items[] = {
{SHD_PHASE_HENYEY_GREENSTEIN,
"HENYEY_GREENSTEIN",
0,
"Henyey-Greenstein",
"Henyey-Greenstein, default phase function for the scattering of light"},
{SHD_PHASE_FOURNIER_FORAND,
"FOURNIER_FORAND",
0,
"Fournier-Forand",
"Fournier-Forand phase function, used for the scattering of light in underwater "
"environments"},
{SHD_PHASE_DRAINE,
"DRAINE",
0,
"Draine",
"Draine phase functions, mostly used for the scattering of light in interstellar dust"},
{SHD_PHASE_RAYLEIGH,
"RAYLEIGH",
0,
"Rayleigh",
"Rayleigh phase function, mostly used for particles smaller than the wavelength of light, "
"such as scattering of sunlight in earth's atmosphere"},
{SHD_PHASE_MIE,
"MIE",
0,
"Mie",
"Approximation of Mie scattering in water droplets, used for scattering in clouds and fog"},
{0, nullptr, 0, nullptr, nullptr},
};
/* -- Common nodes ---------------------------------------------------------- */
static void def_group_input(StructRNA * /*srna*/) {}
@@ -5927,6 +5958,17 @@ static void def_refraction(StructRNA *srna)
RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
}
static void def_scatter(StructRNA *srna)
{
PropertyRNA *prop;
prop = RNA_def_property(srna, "phase", PROP_ENUM, PROP_NONE);
RNA_def_property_enum_sdna(prop, nullptr, "custom1");
RNA_def_property_enum_items(prop, node_scatter_phase_items);
RNA_def_property_ui_text(prop, "Phase", "Phase function for the scattered light");
RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
}
static void def_toon(StructRNA *srna)
{
PropertyRNA *prop;

2
source/blender/nodes/NOD_static_types.h
View File

@@ -76,7 +76,7 @@ DefNode(ShaderNode, SH_NODE_BSDF_HAIR, def_hair, "BSD
DefNode(ShaderNode, SH_NODE_BSDF_HAIR_PRINCIPLED, def_hair_principled, "BSDF_HAIR_PRINCIPLED", BsdfHairPrincipled, "Principled Hair BSDF", "Physically-based, easy-to-use shader for rendering hair and fur")
DefNode(ShaderNode, SH_NODE_SUBSURFACE_SCATTERING, def_sh_subsurface, "SUBSURFACE_SCATTERING",SubsurfaceScattering,"Subsurface Scattering","Subsurface multiple scattering shader to simulate light entering the surface and bouncing internally.\nTypically used for materials such as skin, wax, marble or milk")
DefNode(ShaderNode, SH_NODE_VOLUME_ABSORPTION, 0, "VOLUME_ABSORPTION", VolumeAbsorption, "Volume Absorption", "Absorb light as it passes through the volume")
DefNode(ShaderNode, SH_NODE_VOLUME_SCATTER, 0, "VOLUME_SCATTER", VolumeScatter, "Volume Scatter", "Scatter light as it passes through the volume, often used to add fog to a scene")
DefNode(ShaderNode, SH_NODE_VOLUME_SCATTER, def_scatter, "VOLUME_SCATTER", VolumeScatter, "Volume Scatter", "Scatter light as it passes through the volume, often used to add fog to a scene")
DefNode(ShaderNode, SH_NODE_VOLUME_PRINCIPLED, 0, "PRINCIPLED_VOLUME", VolumePrincipled, "Principled Volume", "Combine all volume shading components into a single easy to use node")
DefNode(ShaderNode, SH_NODE_EMISSION, 0, "EMISSION", Emission, "Emission", "Lambertian emission shader")
DefNode(ShaderNode, SH_NODE_NEW_GEOMETRY, 0, "NEW_GEOMETRY", NewGeometry, "Geometry", "Retrieve geometric information about the current shading point")

72
source/blender/nodes/shader/nodes/node_shader_volume_scatter.cc
View File

@@ -4,6 +4,13 @@
#include "node_shader_util.hh"
#include "BLI_string.h"
#include "UI_interface.hh"
#include "UI_resources.hh"
#include "BKE_node_runtime.hh"
namespace blender::nodes::node_shader_volume_scatter_cc {
static void node_declare(NodeDeclarationBuilder &b)
@@ -16,16 +23,62 @@ static void node_declare(NodeDeclarationBuilder &b)
.default_value(0.0f)
.min(-1.0f)
.max(1.0f)
.subtype(PROP_FACTOR);
.subtype(PROP_FACTOR)
.description(
"Directionality of the scattering. Zero is isotropic, negative is backward, "
"positive is forward");
b.add_input<decl::Float>("IOR")
.default_value(1.33f)
.min(1.0f)
.max(2.0f)
.subtype(PROP_FACTOR)
.description("Index Of Refraction of the scattering particles");
b.add_input<decl::Float>("Backscatter")
.default_value(0.1f)
.min(0.0f)
.max(0.5f)
.subtype(PROP_FACTOR)
.description("Fraction of light that is scattered backwards");
b.add_input<decl::Float>("Alpha").default_value(0.5f).min(0.0f).max(500.0f);
b.add_input<decl::Float>("Diameter")
.default_value(20.0f)
.min(5.0f)
.max(50.0f)
.description("Diameter of the water droplets, in micrometers");
b.add_input<decl::Float>("Weight").available(false);
b.add_output<decl::Shader>("Volume").translation_context(BLT_I18NCONTEXT_ID_ID);
}
#define socket_not_zero(sock) (in[sock].link || (clamp_f(in[sock].vec[0], 0.0f, 1.0f) > 1e-5f))
#define socket_not_black(sock) \
(in[sock].link || (clamp_f(in[sock].vec[0], 0.0f, 1.0f) > 1e-5f && \
clamp_f(in[sock].vec[1], 0.0f, 1.0f) > 1e-5f && \
clamp_f(in[sock].vec[2], 0.0f, 1.0f) > 1e-5f))
static void node_shader_buts_scatter(uiLayout *layout, bContext * /*C*/, PointerRNA *ptr)
{
uiItemR(layout, ptr, "phase", UI_ITEM_R_SPLIT_EMPTY_NAME, "", ICON_NONE);
}
static void node_shader_init_scatter(bNodeTree * /*ntree*/, bNode *node)
{
node->custom1 = SHD_PHASE_HENYEY_GREENSTEIN;
}
static void node_shader_update_scatter(bNodeTree *ntree, bNode *node)
{
const int phase_function = node->custom1;
LISTBASE_FOREACH (bNodeSocket *, sock, &node->inputs) {
if (STR_ELEM(sock->name, "IOR", "Backscatter")) {
bke::node_set_socket_availability(ntree, sock, phase_function == SHD_PHASE_FOURNIER_FORAND);
}
else if (STR_ELEM(sock->name, "Anisotropy")) {
bke::node_set_socket_availability(
ntree, sock, ELEM(phase_function, SHD_PHASE_HENYEY_GREENSTEIN, SHD_PHASE_DRAINE));
}
else if (STR_ELEM(sock->name, "Alpha")) {
bke::node_set_socket_availability(ntree, sock, phase_function == SHD_PHASE_DRAINE);
}
else if (STR_ELEM(sock->name, "Diameter")) {
bke::node_set_socket_availability(ntree, sock, phase_function == SHD_PHASE_MIE);
}
}
}
static int node_shader_gpu_volume_scatter(GPUMaterial *mat,
bNode *node,
@@ -33,7 +86,7 @@ static int node_shader_gpu_volume_scatter(GPUMaterial *mat,
GPUNodeStack *in,
GPUNodeStack *out)
{
if (socket_not_zero(SOCK_DENSITY_ID) && socket_not_black(SOCK_COLOR_ID)) {
if (node_socket_not_zero(in[SOCK_DENSITY_ID]) && node_socket_not_black(in[SOCK_COLOR_ID])) {
/* Consider there is absorption phenomenon when there is scattering since
* `extinction = scattering + absorption`. */
GPU_material_flag_set(mat, GPU_MATFLAG_VOLUME_SCATTER | GPU_MATFLAG_VOLUME_ABSORPTION);
@@ -55,7 +108,12 @@ void register_node_type_sh_volume_scatter()
sh_node_type_base(&ntype, SH_NODE_VOLUME_SCATTER, "Volume Scatter", NODE_CLASS_SHADER);
ntype.declare = file_ns::node_declare;
ntype.add_ui_poll = object_shader_nodes_poll;
ntype.draw_buttons = file_ns::node_shader_buts_scatter;
blender::bke::node_type_size_preset(&ntype, blender::bke::eNodeSizePreset::Middle);
ntype.initfunc = file_ns::node_shader_init_scatter;
ntype.gpu_fn = file_ns::node_shader_gpu_volume_scatter;
ntype.updatefunc = file_ns::node_shader_update_scatter;
blender::bke::node_register_type(&ntype);
}