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, 10 insertions, 20 deletions

diff --git a/source/blender/gpu/shaders/material/gpu_shader_material_subsurface_scattering.glsl b/source/blender/gpu/shaders/material/gpu_shader_material_subsurface_scattering.glsl
index 20b634aa801..c560dd01c4f 100644
--- a/source/blender/gpu/shaders/material/gpu_shader_material_subsurface_scattering.glsl
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_subsurface_scattering.glsl
@@ -1,6 +1,3 @@
-#ifndef VOLUMETRICS
-
-CLOSURE_EVAL_FUNCTION_DECLARE_1(node_subsurface_scattering, Diffuse)
 
 void node_subsurface_scattering(vec4 color,
                                 float scale,
@@ -8,25 +5,18 @@ void node_subsurface_scattering(vec4 color,
                                 float ior,
                                 float anisotropy,
                                 vec3 N,
-                                float sss_id,
+                                float weight,
+                                float do_sss,
                                 out Closure result)
 {
-  CLOSURE_VARS_DECLARE_1(Diffuse);
-
-  in_Diffuse_0.N = N; /* Normalized during eval. */
-  in_Diffuse_0.albedo = color.rgb;
-
-  CLOSURE_EVAL_FUNCTION_1(node_subsurface_scattering, Diffuse);
+  N = safe_normalize(N);
 
-  result = CLOSURE_DEFAULT;
+  ClosureDiffuse diffuse_data;
+  diffuse_data.weight = weight;
+  diffuse_data.color = color.rgb;
+  diffuse_data.N = N;
+  diffuse_data.sss_radius = radius * scale;
+  diffuse_data.sss_id = uint(do_sss);
 
-  closure_load_sss_data(scale, out_Diffuse_0.radiance, color.rgb, int(sss_id), result);
-
-  /* TODO(@fclem): Try to not use this. */
-  closure_load_ssr_data(vec3(0.0), 0.0, in_Diffuse_0.N, -1.0, result);
+  result = closure_eval(diffuse_data);
 }
-
-#else
-/* Stub subsurface scattering because it is not compatible with volumetrics. */
-#  define node_subsurface_scattering(a, b, c, d, e, f, g, h) (h = CLOSURE_DEFAULT)
-#endif