Implement GPU-side dither

Summary:
Uses some magic pseudo-random which is actually a
texture coordinate hashing function.

TODOs:
- Dither noise is the same for all the frames.
- It's different from Floyd's dither we've been
  using before.
- Currently CPU and GPU dithering used different
  implementation. Ideally we need to use the same
  dither in CPU.

Reviewers: brecht

Reviewed By: brecht

Differential Revision: http://developer.blender.org/D58

1 files changed, 20 insertions, 3 deletions

diff --git a/intern/opencolorio/ocio_impl_glsl.cc b/intern/opencolorio/ocio_impl_glsl.cc
index 2af3befc8a9..3a23c266345 100644
--- a/intern/opencolorio/ocio_impl_glsl.cc
+++ b/intern/opencolorio/ocio_impl_glsl.cc
@@ -33,6 +33,7 @@
  *
  */
 
+#include <limits>
 #include <sstream>
 #include <string.h>
 
@@ -62,6 +63,8 @@ typedef struct OCIO_GLSLDrawState {
 
 	float *lut3d;  /* 3D LUT table */
 
+	bool dither_used;
+
 	bool curve_mapping_used;
 	bool curve_mapping_texture_allocated;
 	bool curve_mapping_texture_valid;
@@ -229,10 +232,12 @@ bool OCIOImpl::supportGLSLDraw()
  * restore OpenGL context to it's pre-GLSL draw state.
  */
 bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor,
-                             OCIO_CurveMappingSettings *curve_mapping_settings, bool predivide)
+                             OCIO_CurveMappingSettings *curve_mapping_settings,
+                             float dither, bool predivide)
 {
 	ConstProcessorRcPtr ocio_processor = *(ConstProcessorRcPtr *) processor;
 	bool use_curve_mapping = curve_mapping_settings != NULL;
+	bool use_dither = dither > std::numeric_limits<float>::epsilon();
 
 	/* Create state if needed. */
 	OCIO_GLSLDrawState *state;
@@ -267,7 +272,7 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 
 	/* Step 1: Create a GPU Shader Description */
 	GpuShaderDesc shaderDesc;
-	shaderDesc.setLanguage(GPU_LANGUAGE_GLSL_1_0);
+	shaderDesc.setLanguage(GPU_LANGUAGE_GLSL_1_3);
 	shaderDesc.setFunctionName("OCIODisplay");
 	shaderDesc.setLut3DEdgeLen(LUT3D_EDGE_SIZE);
 
@@ -297,7 +302,8 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 	std::string shaderCacheID = ocio_processor->getGpuShaderTextCacheID(shaderDesc);
 	if (state->program == 0 ||
 	    shaderCacheID != state->shadercacheid ||
-	    use_curve_mapping != state->curve_mapping_used)
+	    use_curve_mapping != state->curve_mapping_used ||
+	    use_dither != state->dither_used)
 	{
 		state->shadercacheid = shaderCacheID;
 
@@ -311,6 +317,12 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 
 		std::ostringstream os;
 
+		os << "#version 130\n";
+
+		if (use_dither) {
+			os << "#define USE_DITHER\n";
+		}
+
 		if (use_curve_mapping) {
 			os << "#define USE_CURVE_MAPPING\n";
 		}
@@ -325,6 +337,7 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 		}
 
 		state->curve_mapping_used = use_curve_mapping;
+		state->dither_used = use_dither;
 	}
 
 	if (state->program) {
@@ -344,6 +357,10 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 		glUniform1i(glGetUniformLocation(state->program, "lut3d_texture"), 1);
 		glUniform1i(glGetUniformLocation(state->program, "predivide"), predivide);
 
+		if (use_dither) {
+			glUniform1f(glGetUniformLocation(state->program, "dither"), dither);
+		}
+
 		if (use_curve_mapping) {
 			glUniform1i(glGetUniformLocation(state->program, "curve_mapping_texture"), 2);
 			glUniform1i(glGetUniformLocation(state->program, "curve_mapping_lut_size"), curve_mapping_settings->lut_size);