WebGPURenderer: Added double-side transmission 2/2 (#29718)

* renders all back-side first in case of materials with transmission

* cleanup

Author: sunag

src/renderers/common/RenderList.js

@@ -1,3 +1,5 @@
+import { DoubleSide } from '../../constants.js';
+
 function painterSortStable( a, b ) {
 
 	if ( a.groupOrder !== b.groupOrder ) {
@@ -46,6 +48,14 @@ function reversePainterSortStable( a, b ) {
 
 }
 
+function needsDoublePass( material ) {
+
+	const hasTransmission = material.transmission > 0 || material.transmissionNode;
+
+	return hasTransmission && material.side === DoubleSide && material.forceSinglePass === false;
+
+}
+
 class RenderList {
 
 	constructor( lighting, scene, camera ) {
@@ -54,6 +64,7 @@ class RenderList {
 		this.renderItemsIndex = 0;
 
 		this.opaque = [];
+		this.transparentDoublePass = [];
 		this.transparent = [];
 		this.bundles = [];
 
@@ -72,6 +83,7 @@ class RenderList {
 		this.renderItemsIndex = 0;
 
 		this.opaque.length = 0;
+		this.transparentDoublePass.length = 0;
 		this.transparent.length = 0;
 		this.bundles.length = 0;
 
@@ -127,15 +139,35 @@ class RenderList {
 
 		if ( object.occlusionTest === true ) this.occlusionQueryCount ++;
 
-		( material.transparent === true || material.transmission > 0 ? this.transparent : this.opaque ).push( renderItem );
+		if ( material.transparent === true || material.transmission > 0 ) {
+
+			if ( needsDoublePass( material ) ) this.transparentDoublePass.push( renderItem );
+
+			this.transparent.push( renderItem );
+
+		} else {
+
+			this.opaque.push( renderItem );
+
+		}
 
 	}
 
 	unshift( object, geometry, material, groupOrder, z, group ) {
 
 		const renderItem = this.getNextRenderItem( object, geometry, material, groupOrder, z, group );
 
-		( material.transparent === true ? this.transparent : this.opaque ).unshift( renderItem );
+		if ( material.transparent === true || material.transmission > 0 ) {
+
+			if ( needsDoublePass( material ) ) this.transparentDoublePass.unshift( renderItem );
+
+			this.transparent.unshift( renderItem );
+
+		} else {
+
+			this.opaque.unshift( renderItem );
+
+		}
 
 	}
 
@@ -154,6 +186,7 @@ class RenderList {
 	sort( customOpaqueSort, customTransparentSort ) {
 
 		if ( this.opaque.length > 1 ) this.opaque.sort( customOpaqueSort || painterSortStable );
+		if ( this.transparentDoublePass.length > 1 ) this.transparentDoublePass.sort( customTransparentSort || reversePainterSortStable );
 		if ( this.transparent.length > 1 ) this.transparent.sort( customTransparentSort || reversePainterSortStable );
 
 	}

src/renderers/common/Renderer.js

@@ -370,7 +370,7 @@ class Renderer {
 		const lightsNode = renderList.lightsNode;
 
 		if ( this.opaque === true && opaqueObjects.length > 0 ) this._renderObjects( opaqueObjects, camera, sceneRef, lightsNode );
-		if ( this.transparent === true && transparentObjects.length > 0 ) this._renderObjects( transparentObjects, camera, sceneRef, lightsNode );
+		if ( this.transparent === true && transparentObjects.length > 0 ) this._renderTransparents( transparentObjects, camera, sceneRef, lightsNode );
 
 		// restore render tree
 
@@ -452,7 +452,7 @@ class Renderer {
 
 			const opaqueObjects = renderList.opaque;
 
-			if ( opaqueObjects.length > 0 ) this._renderObjects( opaqueObjects, camera, sceneRef, lightsNode );
+			if ( this.opaque === true && opaqueObjects.length > 0 ) this._renderObjects( opaqueObjects, camera, sceneRef, lightsNode );
 
 			this._currentRenderBundle = null;
 
@@ -728,13 +728,14 @@ class Renderer {
 		const {
 			bundles,
 			lightsNode,
+			transparentDoublePass: transparentDoublePassObjects,
 			transparent: transparentObjects,
 			opaque: opaqueObjects
 		} = renderList;
 
 		if ( bundles.length > 0 ) this._renderBundles( bundles, sceneRef, lightsNode );
 		if ( this.opaque === true && opaqueObjects.length > 0 ) this._renderObjects( opaqueObjects, camera, sceneRef, lightsNode );
-		if ( this.transparent === true && transparentObjects.length > 0 ) this._renderObjects( transparentObjects, camera, sceneRef, lightsNode );
+		if ( this.transparent === true && transparentObjects.length > 0 ) this._renderTransparents( transparentObjects, transparentDoublePassObjects, camera, sceneRef, lightsNode );
 
 		// finish render pass
 
@@ -1438,7 +1439,47 @@ class Renderer {
 
 	}
 
-	_renderObjects( renderList, camera, scene, lightsNode ) {
+	_renderTransparents( renderList, doublePassList, camera, scene, lightsNode ) {
+
+		if ( doublePassList.length > 0 ) {
+
+			// render back side
+
+			for ( const { material } of doublePassList ) {
+
+				material.side = BackSide;
+
+			}
+
+			this._renderObjects( doublePassList, camera, scene, lightsNode, 'backSide' );
+
+			// render front side
+
+			for ( const { material } of doublePassList ) {
+
+				material.side = FrontSide;
+
+			}
+
+			this._renderObjects( renderList, camera, scene, lightsNode );
+
+			// restore
+
+			for ( const { material } of doublePassList ) {
+
+				material.side = DoubleSide;
+
+			}
+
+		} else {
+
+			this._renderObjects( renderList, camera, scene, lightsNode );
+
+		}
+
+	}
+
+	_renderObjects( renderList, camera, scene, lightsNode, passId = null ) {
 
 		// process renderable objects
 
@@ -1472,23 +1513,23 @@ class Renderer {
 
 						this.backend.updateViewport( this._currentRenderContext );
 
-						this._currentRenderObjectFunction( object, scene, camera2, geometry, material, group, lightsNode );
+						this._currentRenderObjectFunction( object, scene, camera2, geometry, material, group, lightsNode, passId );
 
 					}
 
 				}
 
 			} else {
 
-				this._currentRenderObjectFunction( object, scene, camera, geometry, material, group, lightsNode );
+				this._currentRenderObjectFunction( object, scene, camera, geometry, material, group, lightsNode, passId );
 
 			}
 
 		}
 
 	}
 
-	renderObject( object, scene, camera, geometry, material, group, lightsNode ) {
+	renderObject( object, scene, camera, geometry, material, group, lightsNode, passId = null ) {
 
 		let overridePositionNode;
 		let overrideFragmentNode;
@@ -1570,13 +1611,13 @@ class Renderer {
 			this._handleObjectFunction( object, material, scene, camera, lightsNode, group, 'backSide' ); // create backSide pass id
 
 			material.side = FrontSide;
-			this._handleObjectFunction( object, material, scene, camera, lightsNode, group ); // use default pass id
+			this._handleObjectFunction( object, material, scene, camera, lightsNode, group, passId ); // use default pass id
 
 			material.side = DoubleSide;
 
 		} else {
 
-			this._handleObjectFunction( object, material, scene, camera, lightsNode, group );
+			this._handleObjectFunction( object, material, scene, camera, lightsNode, group, passId );
 
 		}