Properly support alpha

Author: gkjohnson

src/materials/PhysicalPathTracingMaterial.js

@@ -273,7 +273,7 @@ export class PhysicalPathTracingMaterial extends MaterialBase {
 									|| useAlphaTest && albedo.a < alphaTest
 
 									// opacity
-									|| ! useAlphaTest && albedo.a < rand()
+									|| material.transparent && ! useAlphaTest && albedo.a < rand()
 								)
 							) {
 
@@ -580,7 +580,7 @@ export class PhysicalPathTracingMaterial extends MaterialBase {
 							|| useAlphaTest && albedo.a < alphaTest
 
 							// opacity
-							|| ! useAlphaTest && albedo.a < rand()
+							|| material.transparent && ! useAlphaTest && albedo.a < rand()
 						) {
 
 							vec3 point = rayOrigin + rayDirection * dist;

src/shader/shaderStructs.js

@@ -81,6 +81,7 @@ export const shaderMaterialStructs = /* glsl */ `
 		int sheenRoughnessMap;
 
 		bool vertexColors;
+		bool transparent;
 
 		mat3 mapTransform;
 		mat3 metalnessMapTransform;
@@ -192,6 +193,7 @@ export const shaderMaterialStructs = /* glsl */ `
 		m.matte = bool( s14.r );
 		m.castShadow = ! bool( s14.g );
 		m.vertexColors = bool( s14.b );
+		m.transparent = bool( s14.a );
 
 		uint firstTextureTransformIdx = i + 15u;
 

src/uniforms/MaterialsTexture.js

@@ -368,7 +368,7 @@ export class MaterialsTexture extends DataTexture {
 			index ++; // matte
 			index ++; // shadow
 			floatArray[ index ++ ] = Number( m.vertexColors ); // vertexColors
-			index ++;
+			floatArray[ index ++ ] = Number( m.transparent ); // transparent
 
 			// map transform 15
 			index += writeTextureMatrixToArray( m, 'map', floatArray, index );