Fix T97985 EEVEE: Shader mixing not working correctly when reusing shader nodes

This was caused by the `Closure` members being added to the final contribution
more than once. The workaround is to clear the members once a closure has
been added to the final contribution. I used `inout` on `Closure` inputs
so that the render engine implementation of mix and add closure nodes
can do its own thing. The nodegraph handling of inout was changed for this
to work.

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/closure_type_lib.glsl b/source/blender/draw/engines/eevee/shaders/closure_type_lib.glsl
index 9698b5ea6f5..21d347942ca 100644
--- a/source/blender/draw/engines/eevee/shaders/closure_type_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/closure_type_lib.glsl
@@ -87,8 +87,8 @@ Closure closure_eval(ClosureDiffuse diffuse,
                      ClosureReflection clearcoat,
                      ClosureRefraction refraction);
 
-Closure closure_add(Closure cl1, Closure cl2);
-Closure closure_mix(Closure cl1, Closure cl2, float fac);
+Closure closure_add(inout Closure cl1, inout Closure cl2);
+Closure closure_mix(inout Closure cl1, inout Closure cl2, float fac);
 
 float ambient_occlusion_eval(vec3 normal,
                              float distance,