OpenSubdiv: Fix/workaround bad shading on AMD devices

Uniform block data layout was different on CPU and GPU which caused wrong
data being used from shader.

In theory using layout(std140) is what we need to do, but for some reason
such layout specifier is being ignored. This is probably caused by the way
how we exploit extensions from older version of glsl.

For until we've upgraded our glsl pipeline used different approach which
is basically about removing unused fields form the struct manual in hope
that it'll keep memory layout consistent for both CPU and GPU.

This seems to work so far for both NVidia GTX580 and AMD FirePro W8000
here in the studio.

2 files changed, 7 insertions, 3 deletions

diff --git a/intern/opensubdiv/gpu_shader_opensubd_display.glsl b/intern/opensubdiv/gpu_shader_opensubd_display.glsl
index ffc8e3dcaa4..f0f0bb783e6 100644
--- a/intern/opensubdiv/gpu_shader_opensubd_display.glsl
+++ b/intern/opensubdiv/gpu_shader_opensubd_display.glsl
@@ -198,15 +198,17 @@ struct LightSource {
 	vec4 diffuse;
 	vec4 specular;
 	vec4 spotDirection;
+#ifdef SUPPORT_COLOR_MATERIAL
 	float constantAttenuation;
 	float linearAttenuation;
 	float quadraticAttenuation;
 	float spotCutoff;
 	float spotExponent;
 	float spotCosCutoff;
+#endif
 };
 
-uniform Lighting {
+layout(std140) uniform Lighting {
 	LightSource lightSource[MAX_LIGHTS];
 	int num_enabled_lights;
 };
diff --git a/intern/opensubdiv/opensubdiv_gpu_capi.cc b/intern/opensubdiv/opensubdiv_gpu_capi.cc
index 7a57f50d623..f21a8a523e6 100644
--- a/intern/opensubdiv/opensubdiv_gpu_capi.cc
+++ b/intern/opensubdiv/opensubdiv_gpu_capi.cc
@@ -59,19 +59,19 @@ typedef struct Light {
 	float diffuse[4];
 	float specular[4];
 	float spot_direction[4];
+#ifdef SUPPORT_COLOR_MATERIAL
 	float constant_attenuation;
 	float linear_attenuation;
 	float quadratic_attenuation;
 	float spot_cutoff;
 	float spot_exponent;
 	float spot_cos_cutoff;
-	float pad[2];
+#endif
 } Light;
 
 typedef struct Lighting {
 	Light lights[MAX_LIGHTS];
 	int num_enabled;
-	int pad[3];
 } Lighting;
 
 typedef struct Transform {
@@ -444,6 +444,7 @@ void openSubdiv_osdGLMeshDisplayPrepare(int use_osd_glsl,
 		glGetLightfv(GL_LIGHT0 + i,
 		             GL_SPOT_DIRECTION,
 		             g_lighting_data.lights[i].spot_direction);
+#ifdef SUPPORT_COLOR_MATERIAL
 		glGetLightfv(GL_LIGHT0 + i,
 		             GL_CONSTANT_ATTENUATION,
 		             &g_lighting_data.lights[i].constant_attenuation);
@@ -461,6 +462,7 @@ void openSubdiv_osdGLMeshDisplayPrepare(int use_osd_glsl,
 		             &g_lighting_data.lights[i].spot_exponent);
 		g_lighting_data.lights[i].spot_cos_cutoff =
 			cos(g_lighting_data.lights[i].spot_cutoff);
+#endif
 	}
 }