Merge pull request #18171 from Mugen87/dev29

WebGLProgram: Fix derivatives usage for MeshStandardMaterial.

src/renderers/webgl/WebGLProgram.js

@@ -120,7 +120,7 @@ function generateExtensions( extensions, parameters, rendererExtensions ) {
 	extensions = extensions || {};
 
 	var chunks = [
-		( extensions.derivatives || parameters.envMapCubeUV || parameters.bumpMap || parameters.tangentSpaceNormalMap || parameters.clearcoatNormalMap || parameters.flatShading ) ? '#extension GL_OES_standard_derivatives : enable' : '',
+		( extensions.derivatives || parameters.envMapCubeUV || parameters.bumpMap || parameters.tangentSpaceNormalMap || parameters.clearcoatNormalMap || parameters.flatShading || parameters.shaderID === 'physical' ) ? '#extension GL_OES_standard_derivatives : enable' : '',
 		( extensions.fragDepth || parameters.logarithmicDepthBuffer ) && rendererExtensions.get( 'EXT_frag_depth' ) ? '#extension GL_EXT_frag_depth : enable' : '',
 		( extensions.drawBuffers ) && rendererExtensions.get( 'WEBGL_draw_buffers' ) ? '#extension GL_EXT_draw_buffers : require' : '',
 		( extensions.shaderTextureLOD || parameters.envMap ) && rendererExtensions.get( 'EXT_shader_texture_lod' ) ? '#extension GL_EXT_shader_texture_lod : enable' : ''