Fix #36882: cycles gamma node not working with glsl materials.

source/blender/gpu/shaders/gpu_shader_material.glsl

@@ -2134,6 +2134,20 @@ void node_fresnel(float ior, vec3 N, vec3 I, out float result)
 	result = fresnel_dielectric(I, N, (gl_FrontFacing)? eta: 1.0/eta);
 }
 
+/* gamma */
+
+void node_gamma(vec4 col, float gamma, out vec4 outcol)
+{
+	outcol = col;
+
+	if(col.r > 0.0)
+		outcol.r = compatible_pow(col.r, gamma);
+	if(col.g > 0.0)
+		outcol.g = compatible_pow(col.g, gamma);
+	if(col.b > 0.0)
+		outcol.b = compatible_pow(col.b, gamma);
+}
+
 /* geometry */
 
 void node_attribute(vec3 attr_uv, out vec4 outcol, out vec3 outvec, out float outf)

source/blender/nodes/shader/nodes/node_shader_gamma.c

@@ -41,6 +41,11 @@ static bNodeSocketTemplate sh_node_gamma_out[] = {
 	{	-1, 0, ""	}
 };
 
+static int node_shader_gpu_gamma(GPUMaterial *mat, bNode *UNUSED(node), bNodeExecData *UNUSED(execdata), GPUNodeStack *in, GPUNodeStack *out)
+{
+	return GPU_stack_link(mat, "node_gamma", in, out);
+}
+
 void register_node_type_sh_gamma(void)
 {
 	static bNodeType ntype;
@@ -50,6 +55,7 @@ void register_node_type_sh_gamma(void)
 	node_type_socket_templates(&ntype, sh_node_gamma_in, sh_node_gamma_out);
 	node_type_init(&ntype, NULL);
 	node_type_storage(&ntype, "", NULL, NULL);
+	node_type_gpu(&ntype, node_shader_gpu_gamma);
 	
 	nodeRegisterType(&ntype);
 }