fix up the MTL fragment shader so its more overridable

Author: devshgraphicsprogramming

include/nbl/builtin/shader/loader/mtl/fragment_impl.glsl

@@ -84,7 +84,7 @@ vec4 nbl_sample_bump(in vec2 uv, in mat2 dUV) { return texture(map_bump, uv); }
 #include <nbl/builtin/glsl/bxdf/brdf/diffuse/lambert.glsl>
 #include <nbl/builtin/glsl/bxdf/brdf/specular/blinn_phong.glsl>
 
-
+#ifndef _NBL_BUILTIN_GLSL_BUMP_MAPPING_DERIVATIVES_DECLARED_
 mat2x3 nbl_glsl_perturbNormal_dPdSomething() {return mat2x3(dFdx(ViewPos),dFdy(ViewPos));}
 mat2 nbl_glsl_perturbNormal_dUVdSomething()
 {
@@ -95,9 +95,21 @@ mat2 nbl_glsl_perturbNormal_dUVdSomething()
 #endif
 }
 #define _NBL_BUILTIN_GLSL_BUMP_MAPPING_DERIVATIVES_DECLARED_
+#endif
 #include <nbl/builtin/glsl/bump_mapping/utils.glsl>
 
 
+#ifndef _NO_UV
+#ifndef _NBL_FRAG_GET_UV_DERIVATIVES_FUNCTION_DEFINED_
+mat2 nbl_glsl_dUVdScreen()
+{
+    return mat2(dFdx(UV),dFdy(UV));
+}
+#define _NBL_FRAG_GET_UV_DERIVATIVES_FUNCTION_DEFINED_
+#endif
+#endif
+
+
 #ifndef _NBL_BSDF_COS_EVAL_DEFINED_
 #define _NBL_BSDF_COS_EVAL_DEFINED_
 
@@ -109,10 +121,10 @@ mat2 nbl_glsl_perturbNormal_dUVdSomething()
 Spectrum nbl_bsdf_cos_eval(in nbl_glsl_LightSample _sample, in nbl_glsl_IsotropicViewSurfaceInteraction inter)
 {
     nbl_glsl_MTLMaterialParameters mtParams = nbl_glsl_getMaterialParameters();
-    const mat2 dUV = nbl_glsl_perturbNormal_dUVdSomething();
 
     vec3 Kd;
 #ifndef _NO_UV
+    const mat2 dUV = nbl_glsl_dUVdScreen();
     if ((mtParams.extra&(map_Kd_MASK)) == (map_Kd_MASK))
         Kd = nbl_sample_Kd(UV, dUV).rgb;
     else
@@ -181,13 +193,12 @@ Spectrum nbl_bsdf_cos_eval(in nbl_glsl_LightSample _sample, in nbl_glsl_Isotropi
 #ifndef _NBL_COMPUTE_LIGHTING_DEFINED_
 #define _NBL_COMPUTE_LIGHTING_DEFINED_
 
-vec3 nbl_computeLighting(out nbl_glsl_IsotropicViewSurfaceInteraction out_interaction)
+vec3 nbl_computeLighting(in nbl_glsl_IsotropicViewSurfaceInteraction interaction)
 {
-    nbl_glsl_IsotropicViewSurfaceInteraction interaction = nbl_glsl_calcSurfaceInteraction(vec3(0.0), ViewPos, Normal);
     nbl_glsl_MTLMaterialParameters mtParams = nbl_glsl_getMaterialParameters();
 
-    const mat2 dUV = nbl_glsl_perturbNormal_dUVdSomething();
 #ifndef _NO_UV
+    const mat2 dUV = nbl_glsl_dUVdScreen();
     if ((mtParams.extra&map_bump_MASK) == map_bump_MASK)
     {
         interaction.N = normalize(interaction.N);
@@ -230,7 +241,6 @@ vec3 nbl_computeLighting(out nbl_glsl_IsotropicViewSurfaceInteraction out_intera
     break;
     }
 
-    out_interaction = interaction;
 #define Intensity 1000000.0
     return (Intensity/lenL2)*nbl_bsdf_cos_eval(_sample,interaction) + Ka;
 #undef Intensity
@@ -244,7 +254,7 @@ vec3 nbl_computeLighting(out nbl_glsl_IsotropicViewSurfaceInteraction out_intera
 void main()
 {
     nbl_glsl_MTLMaterialParameters mtParams = nbl_glsl_getMaterialParameters();
-    nbl_glsl_IsotropicViewSurfaceInteraction interaction;
+    nbl_glsl_IsotropicViewSurfaceInteraction interaction = nbl_glsl_calcSurfaceInteraction(vec3(0.0),ViewPos,Normal);
     vec3 color = nbl_computeLighting(interaction);
 
     float d = mtParams.d;
@@ -265,7 +275,7 @@ void main()
     #ifndef _NO_UV
             if ((mtParams.extra&(map_d_MASK)) == (map_d_MASK))
             {
-                d = nbl_sample_d(UV, nbl_glsl_perturbNormal_dUVdSomething()).r;
+                d = nbl_sample_d(UV,nbl_glsl_dUVdScreen()).r;
                 color *= d;
             }
     #endif