clean up shadergen ambient handling

fallback needs to a) set the same value as elswhere. b) treat uniforms the same. c) exist on both ends to ensure order of ops doesn't mangle things

Engine/source/shaderGen/GLSL/shaderFeatureGLSL.cpp

@@ -2212,9 +2212,13 @@ void RTLightingFeatGLSL::processPix(   Vector<ShaderComponent*> &componentList,
 
    Var *curColor = (Var*)LangElement::find(getOutputTargetVarName(ShaderFeature::DefaultTarget));
 
-   Var *ambient  = new Var( "ambient", "vec4" );
-   ambient->uniform = true;
-   ambient->constSortPos = cspPass;
+   Var* ambient = (Var*)LangElement::find("ambient");
+   if (!ambient)
+   {
+      ambient = new Var("ambient", "vec4");
+      ambient->uniform = true;
+      ambient->constSortPos = cspPass;
+   }
    
    Var* lighting = new Var("lighting", "vec4");
    meta->addStatement(new GenOp("   @ = compute4Lights( @, @, @, @,\r\n"
@@ -3091,9 +3095,9 @@ void ReflectionProbeFeatGLSL::processPix(Vector<ShaderComponent*>& componentList
    Var *ambient = (Var *)LangElement::find("ambient");
    if (!ambient)
    {
-      ambient = new Var("ambient", "vec3");
-      eyePos->uniform = true;
-      eyePos->constSortPos = cspPass;
+      ambient = new Var("ambient", "vec4");
+      ambient->uniform = true;
+      ambient->constSortPos = cspPass;
    }
    meta->addStatement(new GenOp("   @.rgb *= @.rgb;\r\n", ibl, ambient));
    meta->addStatement(new GenOp("   @.rgb = @.rgb;\r\n", curColor, ibl));

Engine/source/shaderGen/HLSL/shaderFeatureHLSL.cpp

@@ -2284,9 +2284,13 @@ void RTLightingFeatHLSL::processPix(   Vector<ShaderComponent*> &componentList,
 
    Var *curColor = (Var*)LangElement::find(getOutputTargetVarName(ShaderFeature::DefaultTarget));
 
-   Var *ambient  = new Var( "ambient", "float4" );
-   ambient->uniform = true;
-   ambient->constSortPos = cspPass;
+   Var* ambient = (Var*)LangElement::find("ambient");
+   if (!ambient)
+   {
+      ambient = new Var("ambient", "float4");
+      ambient->uniform = true;
+      ambient->constSortPos = cspPass;
+   }
    
    Var* lighting = new Var("lighting", "float4");
    meta->addStatement(new GenOp("   @ = compute4Lights( @, @, @, @,\r\n"
@@ -3179,9 +3183,9 @@ void ReflectionProbeFeatHLSL::processPix(Vector<ShaderComponent*> &componentList
    Var *ambient = (Var *)LangElement::find("ambient");
    if (!ambient)
    {
-      ambient = new Var("ambient","float3");
-      eyePos->uniform = true;
-      eyePos->constSortPos = cspPass;
+      ambient = new Var("ambient","float4");
+      ambient->uniform = true;
+      ambient->constSortPos = cspPass;
    }
    meta->addStatement(new GenOp("   @.rgb *= @.rgb;\r\n", ibl, ambient));
    meta->addStatement(new GenOp("   @.rgb = @.rgb;\r\n", curColor, ibl));