GPU: Make nodetree GLSL Codegen render engine agnostic

This commit removes all EEVEE specific code from the `gpu_shader_material*.glsl`
files. It defines a clear interface to evaluate the closure nodes leaving
more flexibility to the render engine.

Some of the long standing workaround are fixed:
- bump mapping support is no longer duplicating a lot of node and is instead
  compiled into a function call.
- bump rewiring to Normal socket is no longer needed as we now use a global
  `g_data.N` for that.


Closure sampling with upstread weight eval is now supported if the engine needs
it.

This also makes all the material GLSL sources use `GPUSource` for better
debugging experience. The `GPUFunction` parsing now happens in `GPUSource`
creation.

The whole `GPUCodegen` now uses the `ShaderCreateInfo` and is object type
agnostic. Is has also been rewritten in C++.

This patch changes a view behavior for EEVEE:
- Mix shader node factor imput is now clamped.
- Tangent Vector displacement behavior is now matching cycles.
- The chosen BSDF used for SSR might change.
- Hair shading may have very small changes on very large hairs when using hair
  polygon stripes.
- ShaderToRGB node will remove any SSR and SSS form a shader.
- SSS radius input now is no longer a scaling factor but defines an average
  radius. The SSS kernel "shape" (radii) are still defined by the socket default
  values.

Appart from the listed changes no other regressions are expected.

1 files changed, 45 insertions, 56 deletions

diff --git a/source/blender/gpu/shaders/material/gpu_shader_material_eevee_specular.glsl b/source/blender/gpu/shaders/material/gpu_shader_material_eevee_specular.glsl
index 0941482df45..c81880184e3 100644
--- a/source/blender/gpu/shaders/material/gpu_shader_material_eevee_specular.glsl
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_eevee_specular.glsl
@@ -1,80 +1,69 @@
-#ifndef VOLUMETRICS
-
-CLOSURE_EVAL_FUNCTION_DECLARE_3(node_eevee_specular, Diffuse, Glossy, Glossy)
 
 void node_eevee_specular(vec4 diffuse,
                          vec4 specular,
                          float roughness,
                          vec4 emissive,
                          float transp,
-                         vec3 normal,
+                         vec3 N,
                          float clearcoat,
                          float clearcoat_roughness,
-                         vec3 clearcoat_normal,
+                         vec3 CN,
                          float occlusion,
-                         float ssr_id,
+                         float weight,
+                         const float use_clearcoat,
                          out Closure result)
 {
-  CLOSURE_VARS_DECLARE_3(Diffuse, Glossy, Glossy);
-
-  in_common.occlusion = occlusion;
-
-  in_Diffuse_0.N = normal; /* Normalized during eval. */
-  in_Diffuse_0.albedo = diffuse.rgb;
+  N = safe_normalize(N);
+  CN = safe_normalize(CN);
+  vec3 V = cameraVec(g_data.P);
 
-  in_Glossy_1.N = normal; /* Normalized during eval. */
-  in_Glossy_1.roughness = roughness;
+  ClosureEmission emission_data;
+  emission_data.weight = weight;
+  emission_data.emission = emissive.rgb;
 
-  in_Glossy_2.N = clearcoat_normal; /* Normalized during eval. */
-  in_Glossy_2.roughness = clearcoat_roughness;
+  ClosureTransparency transparency_data;
+  transparency_data.weight = weight;
+  transparency_data.transmittance = vec3(transp);
+  transparency_data.holdout = 0.0;
 
-  CLOSURE_EVAL_FUNCTION_3(node_eevee_specular, Diffuse, Glossy, Glossy);
+  float alpha = (1.0 - transp) * weight;
 
-  result = CLOSURE_DEFAULT;
+  ClosureDiffuse diffuse_data;
+  diffuse_data.weight = alpha;
+  diffuse_data.color = diffuse.rgb;
+  diffuse_data.N = N;
+  diffuse_data.sss_id = 0u;
 
-  vec3 V = cameraVec(worldPosition);
-
-  {
-    /* Diffuse. */
-    out_Diffuse_0.radiance = render_pass_diffuse_mask(vec3(1), out_Diffuse_0.radiance);
-    out_Diffuse_0.radiance *= in_Diffuse_0.albedo;
-    result.radiance += out_Diffuse_0.radiance;
-  }
-  {
-    /* Glossy. */
-    float NV = dot(in_Glossy_1.N, V);
-    vec2 split_sum = brdf_lut(NV, in_Glossy_1.roughness);
+  ClosureReflection reflection_data;
+  reflection_data.weight = alpha;
+  if (true) {
+    float NV = dot(N, V);
+    vec2 split_sum = brdf_lut(NV, roughness);
     vec3 brdf = F_brdf_single_scatter(specular.rgb, vec3(1.0), split_sum);
 
-    out_Glossy_1.radiance = closure_mask_ssr_radiance(out_Glossy_1.radiance, ssr_id);
-    out_Glossy_1.radiance *= brdf;
-    out_Glossy_1.radiance = render_pass_glossy_mask(specular.rgb, out_Glossy_1.radiance);
-    closure_load_ssr_data(
-        out_Glossy_1.radiance, in_Glossy_1.roughness, in_Glossy_1.N, ssr_id, result);
+    reflection_data.color = specular.rgb * brdf;
+    reflection_data.N = N;
+    reflection_data.roughness = roughness;
   }
-  {
-    /* Clearcoat. */
-    float NV = dot(in_Glossy_2.N, V);
-    vec2 split_sum = brdf_lut(NV, in_Glossy_2.roughness);
+
+  ClosureReflection clearcoat_data;
+  clearcoat_data.weight = alpha * clearcoat * 0.25;
+  if (true) {
+    float NV = dot(CN, V);
+    vec2 split_sum = brdf_lut(NV, clearcoat_roughness);
     vec3 brdf = F_brdf_single_scatter(vec3(0.04), vec3(1.0), split_sum);
 
-    out_Glossy_2.radiance *= brdf * clearcoat * 0.25;
-    out_Glossy_2.radiance = render_pass_glossy_mask(vec3(1), out_Glossy_2.radiance);
-    result.radiance += out_Glossy_2.radiance;
-  }
-  {
-    /* Emission. */
-    vec3 out_emission_radiance = render_pass_emission_mask(emissive.rgb);
-    result.radiance += out_emission_radiance;
+    clearcoat_data.color = brdf;
+    clearcoat_data.N = CN;
+    clearcoat_data.roughness = clearcoat_roughness;
   }
 
-  float alpha = 1.0 - transp;
-  result.transmittance = vec3(transp);
-  result.radiance *= alpha;
-  result.ssr_data.rgb *= alpha;
+  if (use_clearcoat != 0.0f) {
+    result = closure_eval(diffuse_data, reflection_data, clearcoat_data);
+  }
+  else {
+    result = closure_eval(diffuse_data, reflection_data);
+  }
+  result = closure_add(result, closure_eval(emission_data));
+  result = closure_add(result, closure_eval(transparency_data));
 }
-
-#else
-/* Stub specular because it is not compatible with volumetrics. */
-#  define node_eevee_specular(a, b, c, d, e, f, g, h, i, j, k, result) (result = CLOSURE_DEFAULT)
-#endif