543bf28fb1
wi is the viewing direction, and wo is the illumination direction. Under this notation, BSDF sampling always samples from wi and outputs wo, which is consistent with most of the papers and mitsuba. This order is reversed compared with PBRT, although PBRT also traces from the camera.
72 lines
2.2 KiB
C
72 lines
2.2 KiB
C
/* SPDX-License-Identifier: Apache-2.0
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* Copyright 2011-2022 Blender Foundation */
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#pragma once
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CCL_NAMESPACE_BEGIN
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/* Fresnel Node */
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ccl_device_noinline void svm_node_fresnel(ccl_private ShaderData *sd,
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ccl_private float *stack,
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uint ior_offset,
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uint ior_value,
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uint node)
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{
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uint normal_offset, out_offset;
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svm_unpack_node_uchar2(node, &normal_offset, &out_offset);
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float eta = (stack_valid(ior_offset)) ? stack_load_float(stack, ior_offset) :
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__uint_as_float(ior_value);
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float3 normal_in = stack_valid(normal_offset) ? stack_load_float3(stack, normal_offset) : sd->N;
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eta = fmaxf(eta, 1e-5f);
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eta = (sd->flag & SD_BACKFACING) ? 1.0f / eta : eta;
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float f = fresnel_dielectric_cos(dot(sd->wi, normal_in), eta);
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stack_store_float(stack, out_offset, f);
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}
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/* Layer Weight Node */
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ccl_device_noinline void svm_node_layer_weight(ccl_private ShaderData *sd,
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ccl_private float *stack,
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uint4 node)
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{
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uint blend_offset = node.y;
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uint blend_value = node.z;
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uint type, normal_offset, out_offset;
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svm_unpack_node_uchar3(node.w, &type, &normal_offset, &out_offset);
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float blend = (stack_valid(blend_offset)) ? stack_load_float(stack, blend_offset) :
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__uint_as_float(blend_value);
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float3 normal_in = (stack_valid(normal_offset)) ? stack_load_float3(stack, normal_offset) :
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sd->N;
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float f;
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if (type == NODE_LAYER_WEIGHT_FRESNEL) {
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float eta = fmaxf(1.0f - blend, 1e-5f);
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eta = (sd->flag & SD_BACKFACING) ? eta : 1.0f / eta;
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f = fresnel_dielectric_cos(dot(sd->wi, normal_in), eta);
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}
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else {
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f = fabsf(dot(sd->wi, normal_in));
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if (blend != 0.5f) {
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blend = clamp(blend, 0.0f, 1.0f - 1e-5f);
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blend = (blend < 0.5f) ? 2.0f * blend : 0.5f / (1.0f - blend);
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f = powf(f, blend);
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}
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f = 1.0f - f;
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}
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stack_store_float(stack, out_offset, f);
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}
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CCL_NAMESPACE_END
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