Material: Added onBeforeCompile()

src/materials/Material.js

@@ -69,6 +69,8 @@ Object.assign( Material.prototype, EventDispatcher.prototype, {
 
 	isMaterial: true,
 
+	onBeforeCompile: function () {},
+
 	setValues: function ( values ) {
 
 		if ( values === undefined ) return;

src/renderers/WebGLRenderer.js

@@ -1567,6 +1567,8 @@ function WebGLRenderer( parameters ) {
 
 			material.__webglShader = materialProperties.__webglShader;
 
+			material.onBeforeCompile();
+
 			program = programCache.acquireProgram( material, parameters, code );
 
 			materialProperties.program = program;

src/renderers/webgl/WebGLPrograms.js

@@ -239,6 +239,8 @@ function WebGLPrograms( renderer, capabilities ) {
 
 		}
 
+		array.push( material.onBeforeCompile.toString() );
+
 		array.push( renderer.gammaOutput );
 
 		return array.join();