Minimize glActiveTexture calls (#24492)

* Don't set activetexture for textures that won't be bound

* Fix texture state update of a previously bound texture

* Combine bindTexture and bindTextureToSlot into a single function

src/renderers/webgl/WebGLState.js

@@ -880,25 +880,40 @@ function WebGLState( gl, extensions, capabilities ) {
 
 	}
 
-	function bindTexture( webglType, webglTexture ) {
+	function bindTexture( webglType, webglTexture, webglSlot ) {
 
-		if ( currentTextureSlot === null ) {
+		if ( webglSlot === undefined ) {
 
-			activeTexture();
+			if ( currentTextureSlot === null ) {
+
+				webglSlot = gl.TEXTURE0 + maxTextures - 1;
+
+			} else {
+
+				webglSlot = currentTextureSlot;
+
+			}
 
 		}
 
-		let boundTexture = currentBoundTextures[ currentTextureSlot ];
+		let boundTexture = currentBoundTextures[ webglSlot ];
 
 		if ( boundTexture === undefined ) {
 
 			boundTexture = { type: undefined, texture: undefined };
-			currentBoundTextures[ currentTextureSlot ] = boundTexture;
+			currentBoundTextures[ webglSlot ] = boundTexture;
 
 		}
 
 		if ( boundTexture.type !== webglType || boundTexture.texture !== webglTexture ) {
 
+			if ( currentTextureSlot !== webglSlot ) {
+
+				gl.activeTexture( webglSlot );
+				currentTextureSlot = webglSlot;
+
+			}
+
 			gl.bindTexture( webglType, webglTexture || emptyTextures[ webglType ] );
 
 			boundTexture.type = webglType;

src/renderers/webgl/WebGLTextures.js

@@ -460,8 +460,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 		}
 
-		state.activeTexture( _gl.TEXTURE0 + slot );
-		state.bindTexture( _gl.TEXTURE_2D, textureProperties.__webglTexture );
+		state.bindTexture( _gl.TEXTURE_2D, textureProperties.__webglTexture, _gl.TEXTURE0 + slot );
 
 	}
 
@@ -476,8 +475,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 		}
 
-		state.activeTexture( _gl.TEXTURE0 + slot );
-		state.bindTexture( _gl.TEXTURE_2D_ARRAY, textureProperties.__webglTexture );
+		state.bindTexture( _gl.TEXTURE_2D_ARRAY, textureProperties.__webglTexture, _gl.TEXTURE0 + slot );
 
 	}
 
@@ -492,8 +490,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 		}
 
-		state.activeTexture( _gl.TEXTURE0 + slot );
-		state.bindTexture( _gl.TEXTURE_3D, textureProperties.__webglTexture );
+		state.bindTexture( _gl.TEXTURE_3D, textureProperties.__webglTexture, _gl.TEXTURE0 + slot );
 
 	}
 
@@ -508,8 +505,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 
 		}
 
-		state.activeTexture( _gl.TEXTURE0 + slot );
-		state.bindTexture( _gl.TEXTURE_CUBE_MAP, textureProperties.__webglTexture );
+		state.bindTexture( _gl.TEXTURE_CUBE_MAP, textureProperties.__webglTexture, _gl.TEXTURE0 + slot );
 
 	}
 
@@ -681,13 +677,14 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 		const forceUpload = initTexture( textureProperties, texture );
 		const source = texture.source;
 
-		state.activeTexture( _gl.TEXTURE0 + slot );
-		state.bindTexture( textureType, textureProperties.__webglTexture );
+		state.bindTexture( textureType, textureProperties.__webglTexture, _gl.TEXTURE0 + slot );
 
 		const sourceProperties = properties.get( source );
 
 		if ( source.version !== sourceProperties.__version || forceUpload === true ) {
 
+			state.activeTexture( _gl.TEXTURE0 + slot );
+
 			_gl.pixelStorei( _gl.UNPACK_FLIP_Y_WEBGL, texture.flipY );
 			_gl.pixelStorei( _gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, texture.premultiplyAlpha );
 			_gl.pixelStorei( _gl.UNPACK_ALIGNMENT, texture.unpackAlignment );
@@ -1042,13 +1039,14 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 		const forceUpload = initTexture( textureProperties, texture );
 		const source = texture.source;
 
-		state.activeTexture( _gl.TEXTURE0 + slot );
-		state.bindTexture( _gl.TEXTURE_CUBE_MAP, textureProperties.__webglTexture );
+		state.bindTexture( _gl.TEXTURE_CUBE_MAP, textureProperties.__webglTexture, _gl.TEXTURE0 + slot );
 
 		const sourceProperties = properties.get( source );
 
 		if ( source.version !== sourceProperties.__version || forceUpload === true ) {
 
+			state.activeTexture( _gl.TEXTURE0 + slot );
+
 			_gl.pixelStorei( _gl.UNPACK_FLIP_Y_WEBGL, texture.flipY );
 			_gl.pixelStorei( _gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, texture.premultiplyAlpha );
 			_gl.pixelStorei( _gl.UNPACK_ALIGNMENT, texture.unpackAlignment );