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GPU: Add GL_ARB_clip_control support to the GL backend

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This adds support for the extension and always
set the clip state value to 0..1 to align with vulkan
and metal. Moreover this is needed for the Reverse Z
implementation.

Note that this is a OpenGL 4.5 feature and is not
required to start Blender. So there must still be
a fallback path for now.

Rel #138898

Pull Request: https://projects.blender.org/blender/blender/pulls/138941
This commit is contained in:
Clément Foucault
2025-05-16 13:53:36 +02:00
committed by Clément Foucault
parent 45240026a2
commit 8ac5940e33
12 changed files with 67 additions and 0 deletions
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7
source/blender/draw/engines/eevee/eevee_shader.cc
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@@ -639,6 +639,13 @@ void ShaderModule::material_create_info_amend(GPUMaterial *gpumat, GPUCodegenOut
}
}
#if 0 /* Waiting for using DRW_STATE_CLIP_CONTROL_UNIT_RANGE where these are used. */
if (geometry_type != MAT_GEOM_WORLD) {
/* Allow to use Reverse-Z on OpenGL. Does nothing in other backend. */
info.builtins(BuiltinBits::CLIP_CONTROL);
}
#endif
std::stringstream global_vars;
switch (geometry_type) {
case MAT_GEOM_MESH:

7
source/blender/draw/intern/draw_command.cc
View File

@@ -305,6 +305,13 @@ void StateSet::execute(RecordingState &recording_state) const
to_stencil_op(new_state),
to_provoking_vertex(new_state));
if (new_state & DRW_STATE_CLIP_CONTROL_UNIT_RANGE) {
GPU_clip_control_unit_range(true);
}
else {
GPU_clip_control_unit_range(false);
}
if (new_state & DRW_STATE_SHADOW_OFFSET) {
GPU_shadow_offset(true);
}

2
source/blender/draw/intern/draw_state.hh
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@@ -64,6 +64,8 @@ typedef enum {
DRW_STATE_LOGIC_INVERT = (10 << 11),
DRW_STATE_BLEND_ALPHA_UNDER_PREMUL = (11 << 11),
/* See GPU_clip_control_unit_range. */
DRW_STATE_CLIP_CONTROL_UNIT_RANGE = (1 << 26),
DRW_STATE_IN_FRONT_SELECT = (1 << 27),
DRW_STATE_SHADOW_OFFSET = (1 << 28),
DRW_STATE_CLIP_PLANES = (1 << 29),

5
source/blender/gpu/GPU_state.hh
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@@ -194,6 +194,11 @@ void GPU_stencil_reference_set(uint reference);
void GPU_stencil_write_mask_set(uint write_mask);
void GPU_stencil_compare_mask_set(uint compare_mask);
/* Sets the depth range to be 0..1. Only have effect with the OpenGL backend. Have no effect if
* glClipControl is not supported. Shaders used for drawing with this state must use
* BuiltinBits::CLIP_CONTROL for their vertex shader to be patched. */
void GPU_clip_control_unit_range(bool enable);
eGPUFaceCullTest GPU_face_culling_get();
eGPUBlend GPU_blend_get();
eGPUDepthTest GPU_depth_test_get();

4
source/blender/gpu/intern/gpu_shader_create_info.hh
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@@ -422,6 +422,10 @@ enum class BuiltinBits {
/* Texture atomics requires usage options to alter compilation flag. */
TEXTURE_ATOMIC = (1 << 18),
/* Enable shader patching on GL to remap clip range to 0..1.
* Will do nothing if ClipControl is unsupporteds. */
CLIP_CONTROL = (1 << 19),
/* Not a builtin but a flag we use to tag shaders that use the debug features. */
USE_PRINTF = (1 << 28),
USE_DEBUG_DRAW = (1 << 29),

6
source/blender/gpu/intern/gpu_state.cc
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@@ -145,6 +145,11 @@ void GPU_state_set(eGPUWriteMask write_mask,
state.provoking_vert = uint32_t(provoking_vert);
}
void GPU_clip_control_unit_range(bool enable)
{
SET_IMMUTABLE_STATE(clip_control, enable);
}
/** \} */
/* -------------------------------------------------------------------- */
@@ -423,6 +428,7 @@ StateManager::StateManager()
state.invert_facing = false;
state.shadow_bias = false;
state.clip_distances = 0;
state.clip_control = false;
state.polygon_smooth = false;
state.line_smooth = false;

2
source/blender/gpu/intern/gpu_state_private.hh
View File

@@ -40,6 +40,8 @@ union GPUState {
uint32_t logic_op_xor : 1;
uint32_t invert_facing : 1;
uint32_t shadow_bias : 1;
/** Clip range of 0..1 on OpenGL. */
uint32_t clip_control : 1;
/** Number of clip distances enabled. */
/* TODO(fclem): This should be a shader property. */
uint32_t clip_distances : 3;

3
source/blender/gpu/opengl/gl_backend.cc
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@@ -413,6 +413,7 @@ static void detect_workarounds()
GLContext::multi_bind_support = false;
GLContext::multi_bind_image_support = false;
/* Turn off OpenGL 4.5 features. */
GLContext::clip_control_support = false;
GLContext::direct_state_access_support = false;
/* Turn off OpenGL 4.6 features. */
GLContext::texture_filter_anisotropic_support = false;
@@ -612,6 +613,7 @@ GLint GLContext::max_ssbo_binds = 0;
/** Extensions. */
bool GLContext::clip_control_support = false;
bool GLContext::debug_layer_support = false;
bool GLContext::direct_state_access_support = false;
bool GLContext::explicit_location_support = false;
@@ -710,6 +712,7 @@ void GLBackend::capabilities_init()
GLContext::stencil_texturing_support = epoxy_gl_version() >= 43;
GLContext::texture_filter_anisotropic_support = epoxy_has_gl_extension(
"GL_EXT_texture_filter_anisotropic");
GLContext::clip_control_support = epoxy_has_gl_extension("GL_ARB_clip_control");
/* Disabled until it is proven to work. */
GLContext::framebuffer_fetch_support = false;

1
source/blender/gpu/opengl/gl_context.hh
View File

@@ -48,6 +48,7 @@ class GLContext : public Context {
/** Extensions. */
static bool clip_control_support;
static bool debug_layer_support;
static bool direct_state_access_support;
static bool explicit_location_support;

13
source/blender/gpu/opengl/gl_shader.cc
View File

@@ -711,6 +711,13 @@ std::string GLShader::vertex_interface_declare(const ShaderCreateInfo &info) con
ss << "#define gpu_ViewportIndex gl_ViewportIndex\n";
}
}
if (bool(info.builtins_ & BuiltinBits::CLIP_CONTROL)) {
if (GLContext::clip_control_support && !has_geometry_stage) {
/* Assume clip range is set to 0..1 and remap the range just like Vulkan and Metal.
* If geometry stage is needed, do that remapping inside the geometry shader stage. */
post_main += "gl_Position.z = (gl_Position.z + gl_Position.w) * 0.5;\n";
}
}
if (bool(info.builtins_ & BuiltinBits::BARYCENTRIC_COORD)) {
if (!GLContext::native_barycentric_support) {
/* Disabled or unsupported. */
@@ -983,6 +990,12 @@ std::string GLShader::workaround_geometry_shader_source_create(
ss << " vec3(" << int(i == 0) << ", " << int(i == 1) << ", " << int(i == 2) << ");\n";
}
ss << " gl_Position = gl_in[" << i << "].gl_Position;\n";
if (bool(info.builtins_ & BuiltinBits::CLIP_CONTROL)) {
if (GLContext::clip_control_support) {
/* Assume clip range is set to 0..1 and remap the range just like Vulkan and Metal. */
ss << "gl_Position.z = (gl_Position.z + gl_Position.w) * 0.5;\n";
}
}
if (do_layer_output) {
ss << " gl_Layer = gpu_Layer[" << i << "];\n";
}

16
source/blender/gpu/opengl/gl_state.cc
View File

@@ -109,6 +109,9 @@ void GLStateManager::set_state(const GPUState &state)
if (changed.shadow_bias != 0) {
set_shadow_bias(state.shadow_bias);
}
if (changed.clip_control != 0) {
set_clip_control(state.clip_control);
}
/* TODO: remove. */
if (changed.polygon_smooth) {
@@ -330,6 +333,19 @@ void GLStateManager::set_shadow_bias(const bool enable)
}
}
void GLStateManager::set_clip_control(const bool enable)
{
if (GLContext::clip_control_support) {
if (enable) {
/* Match Vulkan and Metal by default. */
glClipControl(GL_LOWER_LEFT, GL_ZERO_TO_ONE);
}
else {
glClipControl(GL_LOWER_LEFT, GL_NEGATIVE_ONE_TO_ONE);
}
}
}
void GLStateManager::set_blend(const eGPUBlend value)
{
/**

1
source/blender/gpu/opengl/gl_state.hh
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@@ -94,6 +94,7 @@ class GLStateManager : public StateManager {
static void set_backface_culling(eGPUFaceCullTest test);
static void set_provoking_vert(eGPUProvokingVertex vert);
static void set_shadow_bias(bool enable);
static void set_clip_control(bool enable);
static void set_blend(eGPUBlend value);
void set_state(const GPUState &state);