WebGLRenderer: Save/restore textureUnits on render state stack (#33217)

src/renderers/WebGLRenderer.js

@@ -1652,6 +1652,7 @@ class WebGLRenderer {
 			currentRenderState = renderStates.get( scene, renderStateStack.length );
 			currentRenderState.init( camera );
 
+			currentRenderState.state.textureUnits = textures.getTextureUnits();
 			renderStateStack.push( currentRenderState );
 
 			_projScreenMatrix.multiplyMatrices( camera.projectionMatrix, camera.matrixWorldInverse );
@@ -1797,6 +1798,8 @@ class WebGLRenderer {
 
 				currentRenderState = renderStateStack[ renderStateStack.length - 1 ];
 
+				textures.setTextureUnits( currentRenderState.state.textureUnits );
+
 				if ( _clippingEnabled === true ) clipping.setGlobalState( _this.clippingPlanes, currentRenderState.state.camera );
 
 			} else {

src/renderers/webgl/WebGLRenderStates.js

@@ -48,7 +48,8 @@ function WebGLRenderState( extensions ) {
 
 		lights: lights,
 
-		transmissionRenderTarget: {}
+		transmissionRenderTarget: {},
+		textureUnits: 0
 	};
 
 	return {

src/renderers/webgl/WebGLTextures.js

@@ -468,6 +468,18 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 	}
 
+	function getTextureUnits() {
+
+		return textureUnits;
+
+	}
+
+	function setTextureUnits( value ) {
+
+		textureUnits = value;
+
+	}
+
 	function allocateTextureUnit() {
 
 		const textureUnit = textureUnits;
@@ -2386,6 +2398,8 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 	this.allocateTextureUnit = allocateTextureUnit;
 	this.resetTextureUnits = resetTextureUnits;
+	this.getTextureUnits = getTextureUnits;
+	this.setTextureUnits = setTextureUnits;
 
 	this.setTexture2D = setTexture2D;
 	this.setTexture2DArray = setTexture2DArray;