WebGLRenderer: Support MRT for 2d array textures (#31476)

src/renderers/WebGLRenderer.js

@@ -2811,9 +2811,15 @@ class WebGLRenderer {
 
 			} else if ( isRenderTarget3D ) {
 
-				const textureProperties = properties.get( renderTarget.texture );
 				const layer = activeCubeFace;
-				_gl.framebufferTextureLayer( _gl.FRAMEBUFFER, _gl.COLOR_ATTACHMENT0, textureProperties.__webglTexture, activeMipmapLevel, layer );
+
+				for ( let i = 0; i < renderTarget.textures.length; i ++ ) {
+
+					const textureProperties = properties.get( renderTarget.textures[ i ] );
+
+					_gl.framebufferTextureLayer( _gl.FRAMEBUFFER, _gl.COLOR_ATTACHMENT0 + i, textureProperties.__webglTexture, activeMipmapLevel, layer );
+
+				}
 
 			} else if ( renderTarget !== null && activeMipmapLevel !== 0 ) {
 

src/renderers/webgl/WebGLTextures.js

@@ -544,7 +544,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 		const textureProperties = properties.get( texture );
 
-		if ( texture.version > 0 && textureProperties.__version !== texture.version ) {
+		if ( texture.isRenderTargetTexture === false && texture.version > 0 && textureProperties.__version !== texture.version ) {
 
 			uploadTexture( textureProperties, texture, slot );
 			return;
@@ -559,7 +559,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 		const textureProperties = properties.get( texture );
 
-		if ( texture.version > 0 && textureProperties.__version !== texture.version ) {
+		if ( texture.isRenderTargetTexture === false && texture.version > 0 && textureProperties.__version !== texture.version ) {
 
 			uploadTexture( textureProperties, texture, slot );
 			return;
@@ -2002,13 +2002,21 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 				const attachment = textures[ i ];
 				const attachmentProperties = properties.get( attachment );
 
-				state.bindTexture( _gl.TEXTURE_2D, attachmentProperties.__webglTexture );
-				setTextureParameters( _gl.TEXTURE_2D, attachment );
-				setupFrameBufferTexture( renderTargetProperties.__webglFramebuffer, renderTarget, attachment, _gl.COLOR_ATTACHMENT0 + i, _gl.TEXTURE_2D, 0 );
+				let glTextureType = _gl.TEXTURE_2D;
+
+				if ( renderTarget.isWebGL3DRenderTarget || renderTarget.isWebGLArrayRenderTarget ) {
+
+					glTextureType = renderTarget.isWebGL3DRenderTarget ? _gl.TEXTURE_3D : _gl.TEXTURE_2D_ARRAY;
+
+				}
+
+				state.bindTexture( glTextureType, attachmentProperties.__webglTexture );
+				setTextureParameters( glTextureType, attachment );
+				setupFrameBufferTexture( renderTargetProperties.__webglFramebuffer, renderTarget, attachment, _gl.COLOR_ATTACHMENT0 + i, glTextureType, 0 );
 
 				if ( textureNeedsGenerateMipmaps( attachment ) ) {
 
-					generateMipmap( _gl.TEXTURE_2D );
+					generateMipmap( glTextureType );
 
 				}