WebGLProgram: Fix transmission check in generateExtensions(). (#22377)

src/renderers/webgl/WebGLProgram.js

@@ -117,7 +117,7 @@ function generateExtensions( parameters ) {
 		( parameters.extensionDerivatives || parameters.envMapCubeUV || parameters.bumpMap || parameters.tangentSpaceNormalMap || parameters.clearcoatNormalMap || parameters.flatShading || parameters.shaderID === 'physical' ) ? '#extension GL_OES_standard_derivatives : enable' : '',
 		( parameters.extensionFragDepth || parameters.logarithmicDepthBuffer ) && parameters.rendererExtensionFragDepth ? '#extension GL_EXT_frag_depth : enable' : '',
 		( parameters.extensionDrawBuffers && parameters.rendererExtensionDrawBuffers ) ? '#extension GL_EXT_draw_buffers : require' : '',
-		( parameters.extensionShaderTextureLOD || parameters.envMap || parameters.transmission > 0.0 ) && parameters.rendererExtensionShaderTextureLod ? '#extension GL_EXT_shader_texture_lod : enable' : ''
+		( parameters.extensionShaderTextureLOD || parameters.envMap || parameters.transmission ) && parameters.rendererExtensionShaderTextureLod ? '#extension GL_EXT_shader_texture_lod : enable' : ''
 	];
 
 	return chunks.filter( filterEmptyLine ).join( '\n' );

src/renderers/webgl/WebGLPrograms.js

@@ -206,7 +206,7 @@ function WebGLPrograms( renderer, cubemaps, cubeuvmaps, extensions, capabilities
 
 			sheen: !! material.sheen,
 
-			transmission: !! material.transmission,
+			transmission: material.transmission > 0,
 			transmissionMap: !! material.transmissionMap,
 			thicknessMap: !! material.thicknessMap,