From 7a9d0282db6d285aee6edc691635599dbba63ee9 Mon Sep 17 00:00:00 2001
From: aardgoose <angus.sawyer@email.com>
Date: Mon, 23 Oct 2023 16:21:27 +0100
Subject: [PATCH] first pass minimise binds

implement destroyTexture
---
 examples/jsm/renderers/webgl/WebGLBackend.js | 111 +++++++++++++------
 1 file changed, 76 insertions(+), 35 deletions(-)

diff --git a/examples/jsm/renderers/webgl/WebGLBackend.js b/examples/jsm/renderers/webgl/WebGLBackend.js
index 1f72606d4f0371..2f3e1081960ebd 100644
--- a/examples/jsm/renderers/webgl/WebGLBackend.js
+++ b/examples/jsm/renderers/webgl/WebGLBackend.js
@@ -43,6 +43,10 @@ class WebGLBackend extends Backend {
 		this.extensions.get( 'EXT_color_buffer_float' );
 		this._currentContext = null;
 
+		this.maxTexture = this.gl.getParameter( this.gl.MAX_TEXTURE_IMAGE_UNITS );
+		this.activeTextureUnit = null;
+		this.textureBindings = Array( this.maxTexture );
+
 	}
 
 	get coordinateSystem() {
@@ -312,8 +316,7 @@ class WebGLBackend extends Backend {
 
 			} else if ( binding.isSampledTexture ) {
 
-				gl.activeTexture( gl.TEXTURE0 + index );
-				gl.bindTexture( bindingData.glTextureType, bindingData.textureGPU );
+				this._bindTexture( binding.texture, index );
 
 			}
 
@@ -455,12 +458,26 @@ class WebGLBackend extends Backend {
 		const glTextureType = textureUtils.getGLTextureType( texture );
 
 		let textureGPU = defaultTextures[ glTextureType ];
+		let firstUse = false;
 
 		if ( textureGPU === undefined ) {
 
 			textureGPU = gl.createTexture();
+			firstUse = true;
+
+		}
+
+		this.set( texture, {
+			textureGPU,
+			glTextureType,
+			isDefault: true,
+			unit: null
+		} );
+
+		if ( firstUse ) {
+
+			this._bindTexture( texture );
 
-			gl.bindTexture( glTextureType, textureGPU );
 			gl.texParameteri( glTextureType, gl.TEXTURE_MIN_FILTER, gl.NEAREST );
 			gl.texParameteri( glTextureType, gl.TEXTURE_MAG_FILTER, gl.NEAREST );
 
@@ -470,12 +487,6 @@ class WebGLBackend extends Backend {
 
 		}
 
-		this.set( texture, {
-			textureGPU,
-			glTextureType,
-			isDefault: true
-		} );
-
 	}
 
 	createTexture( texture, options ) {
@@ -490,7 +501,16 @@ class WebGLBackend extends Backend {
 		const textureGPU = gl.createTexture();
 		const glTextureType = textureUtils.getGLTextureType( texture );
 
-		gl.bindTexture( glTextureType, textureGPU );
+		this.set( texture, {
+			textureGPU,
+			glTextureType,
+			glFormat,
+			glType,
+			glInternalFormat,
+			unit: null
+		} );
+
+		this._bindTexture( texture );
 
 		gl.pixelStorei( gl.UNPACK_FLIP_Y_WEBGL, texture.flipY );
 		gl.pixelStorei( gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, texture.premultiplyAlpha );
@@ -499,29 +519,19 @@ class WebGLBackend extends Backend {
 
 		textureUtils.setTextureParameters( glTextureType, texture );
 
-		gl.bindTexture( glTextureType, textureGPU );
-
 		if ( ! texture.isVideoTexture ) {
 
 			gl.texStorage2D( glTextureType, levels, glInternalFormat, width, height );
 
 		}
 
-		this.set( texture, {
-			textureGPU,
-			glTextureType,
-			glFormat,
-			glType,
-			glInternalFormat
-		} );
-
 	}
 
 	updateTexture( texture, options ) {
 
 		const { gl } = this;
 		const { width, height } = options;
-		const { textureGPU, glTextureType, glFormat, glType, glInternalFormat } = this.get( texture );
+		const { glTextureType, glFormat, glType, glInternalFormat } = this._bindTexture( texture );
 
 		const getImage = ( source ) => {
 
@@ -539,8 +549,6 @@ class WebGLBackend extends Backend {
 
 		};
 
-		gl.bindTexture( glTextureType, textureGPU );
-
 		if ( texture.isCubeTexture ) {
 
 			const images = options.images;
@@ -573,16 +581,22 @@ class WebGLBackend extends Backend {
 	generateMipmaps( texture ) {
 
 		const { gl } = this;
-		const { textureGPU, glTextureType } = this.get( texture );
+		const { glTextureType } = this._bindTexture( texture );
 
-		gl.bindTexture( glTextureType, textureGPU );
 		gl.generateMipmap( glTextureType );
 
 	}
 
-	destroyTexture( /*texture*/ ) {
+	destroyTexture( texture ) {
 
-		console.warn( 'Abstract class.' );
+		const { gl } = this;
+		const { textureGPU } = this.get( texture );
+
+		this.textureBindings[ textureGPU ] = null;
+
+		gl.deleteTexture( textureGPU );
+
+		this.delete( texture );
 
 	}
 
@@ -785,12 +799,8 @@ class WebGLBackend extends Backend {
 
 			} else if ( binding.isSampledTexture ) {
 
-				const { textureGPU, glTextureType } = this.get( binding.texture );
-
 				this.set( binding, {
-					index: textureIndex ++,
-					textureGPU,
-					glTextureType
+					index: textureIndex ++
 				} );
 
 			}
@@ -890,10 +900,9 @@ class WebGLBackend extends Backend {
 
 		} else {
 
-			gl.bindTexture( gl.TEXTURE_2D, textureGPU );
-			gl.copyTexSubImage2D( gl.TEXTURE_2D, 0, 0, 0, 0, 0, width, height );
+			this._bindTexture( texture );
 
-			gl.bindTexture( gl.TEXTURE_2D, null );
+			gl.copyTexSubImage2D( gl.TEXTURE_2D, 0, 0, 0, 0, 0, width, height );
 
 		}
 
@@ -962,6 +971,38 @@ class WebGLBackend extends Backend {
 
 	}
 
+	_bindTexture( texture, unit ) {
+
+		const textureData = this.get( texture );
+
+		const { gl, textureBindings, maxTexture } = this;
+		const { glTextureType, textureGPU } = textureData;
+
+		if ( unit === undefined ) unit = textureData.unit === null ? maxTexture - 1 : textureData.unit;
+
+		if ( this.activeTextureUnit !== unit ) {
+
+			gl.activeTexture( gl.TEXTURE0 + unit );
+			this.activeTextureUnit = unit;
+
+		}
+
+		if ( textureBindings[ unit ] !== textureGPU ) {
+
+			const oldBinding = textureBindings[ unit ];
+			if ( oldBinding !== undefined ) oldBinding.unit = null;
+
+			gl.bindTexture( glTextureType, textureGPU );
+
+			textureBindings[ unit ] = textureGPU;
+			textureData.unit = unit;
+
+		}
+
+		return textureData;
+
+	}
+
 }
 
 export default WebGLBackend;