WebGLProgram: Refactor GLSL conversion.

src/renderers/webgl/WebGLProgram.js

@@ -1,7 +1,7 @@
 import { WebGLUniforms } from './WebGLUniforms.js';
 import { WebGLShader } from './WebGLShader.js';
 import { ShaderChunk } from '../shaders/ShaderChunk.js';
-import { NoToneMapping, AddOperation, MixOperation, MultiplyOperation, CubeRefractionMapping, CubeUVRefractionMapping, CubeUVReflectionMapping, CubeReflectionMapping, PCFSoftShadowMap, PCFShadowMap, VSMShadowMap, ACESFilmicToneMapping, CineonToneMapping, CustomToneMapping, ReinhardToneMapping, LinearToneMapping, GammaEncoding, RGBDEncoding, RGBM16Encoding, RGBM7Encoding, RGBEEncoding, sRGBEncoding, LinearEncoding, LogLuvEncoding } from '../../constants.js';
+import { NoToneMapping, AddOperation, MixOperation, MultiplyOperation, CubeRefractionMapping, CubeUVRefractionMapping, CubeUVReflectionMapping, CubeReflectionMapping, PCFSoftShadowMap, PCFShadowMap, VSMShadowMap, ACESFilmicToneMapping, CineonToneMapping, CustomToneMapping, ReinhardToneMapping, LinearToneMapping, GammaEncoding, RGBDEncoding, RGBM16Encoding, RGBM7Encoding, RGBEEncoding, sRGBEncoding, LinearEncoding, LogLuvEncoding, GLSL3 } from '../../constants.js';
 
 let programIdCount = 0;
 
@@ -667,11 +667,9 @@ function WebGLProgram( renderer, cacheKey, parameters, bindingStates ) {
 	vertexShader = unrollLoops( vertexShader );
 	fragmentShader = unrollLoops( fragmentShader );
 
-	if ( ( parameters.glslVersion === null || parameters.glslVersion === undefined ) &&
-	       parameters.isWebGL2 && ! parameters.isRawShaderMaterial ) {
+	if ( parameters.isWebGL2 && ! parameters.isRawShaderMaterial ) {
 
-		// Automated GLSL 3.0 conversion. The shader chunks of standard shaders (eg MeshStandardMaterial) require GLSL 3.0 features within WebGL2.
-		// Apply these conversions if no glslVersion is specified.
+		// overwrite GLSL version for built-in materials
 
 		versionString = '#version 300 es\n';
 
@@ -683,8 +681,8 @@ function WebGLProgram( renderer, cacheKey, parameters, bindingStates ) {
 
 		prefixFragment = [
 			'#define varying in',
-			'out highp vec4 pc_fragColor;',
-			'#define gl_FragColor pc_fragColor',
+			( parameters.glslVersion === GLSL3 ) ? '' : 'out highp vec4 pc_fragColor;',
+			( parameters.glslVersion === GLSL3 ) ? '' : '#define gl_FragColor pc_fragColor',
 			'#define gl_FragDepthEXT gl_FragDepth',
 			'#define texture2D texture',
 			'#define textureCube texture',