cocos2d-js Shader系列3：多重纹理 multiple textures multiple samplers

上一篇，我们学习了怎么便捷的控制sprite的颜色，而这个都是默认一个texture的，如果要实现类似mask的效果，或者更个性化的多纹理效果，怎么实现呢？

这就是这一节需要介绍的内容。

例如上图的效果，下方2个球是原图，而上方的图就是由2个球通过某个公式合成的效果了。这里重点不是怎么合成，而是怎么把多个纹理推送到fragment shader中。

相信大家都会想到，首先需要在fragment shader中添加多一个Sample2D：

uniform sampler2D CC_Texture0
uniform sampler2D CC_Texture1

但是通过简单的绑定纹理，只能绑定到第一个sampler上：

this.tex1 = cc.textureCache.addImage("res2/item_2.png");
gl.bindTexture(gl.TEXTURE_2D, this.tex1)

那么关键点来了，我们需要利用gl的32个texture缓存。

this.tex1Location = gl.getUniformLocation(p, "CC_Texture0");
this.tex2Location = gl.getUniformLocation(p, "CC_Texture1");

gl.activeTexture(gl.TEXTURE0);          //webgl中一共32个，可以看cocos2d列的常量
gl.bindTexture(gl.TEXTURE_2D, this.tex1.getName());
gl.uniform1i(this.tex1Location, 0);     //把CC_Texture0指向gl.TEXTURE0
gl.activeTexture(gl.TEXTURE1);
gl.bindTexture(gl.TEXTURE_2D, this.tex2.getName());
gl.uniform1i(this.tex1Location, 1);

核心是先激活某个纹理缓存，然后绑定sampler2D到对应的位置。最后，我们需要记得在draw之后清空，否则会影响下一个Node的绘制。

gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, null);
gl.activeTexture(gl.TEXTURE1);
gl.bindTexture(gl.TEXTURE_2D, null);
gl.bindBuffer(gl.ARRAY_BUFFER, null);

全部代码：

var MultiTexturesLayer = cc.Layer.extend({
    ctor:function() {
        this._super();
        if( 'opengl' in cc.sys.capabilities ) {
            var node1 = new cc.Sprite("res2/item_2.png");
            var node2 = new cc.Sprite("res2/item_3.png");
            this.addChild(node1);
            this.addChild(node2);
            node1.x = 500;
            node2.x = 200;
            node1.y = node2.y = 400;
            var glnode = new cc.Node();
            this.addChild(glnode,10);
            this.glnode = glnode;
            var winSize = cc.director.getWinSize();
            glnode.x = winSize.width/2;
            glnode.y = winSize.height/2;
            glnode.width = 128;
            glnode.height = 128;
            glnode.anchorX = 0.5;
            glnode.anchorY = 0.5;
            var MULTI_TEXTURES_FRAGMENT_SHADER =
                "precision lowp float;   \n"
                + "varying vec2 v_texCoord;  \n"
                + "uniform sampler2D CC_Texture0; \n"
                + "uniform sampler2D CC_Texture1; \n"
                + "void main() \n"
                + "{  \n"
                    + "    vec4 color1 =  texture2D(CC_Texture0, v_texCoord);   \n"
                    + "    vec4 color2 =  texture2D(CC_Texture1, v_texCoord);   \n"
                    + "    gl_FragColor = vec4(color1.r*color2.r, color1.g*color2.g, color1.b*color2.b, color1.a*color2.a);   \n"
                + "}";
            var DEFAULT_VERTEX_SHADER =
                "attribute vec4 a_position; \n"
                + "attribute vec2 a_texCoord; \n"
                + "varying mediump vec2 v_texCoord; \n"
                + "void main() \n"
                + "{ \n"
                + "    gl_Position = (CC_PMatrix * CC_MVMatrix) * a_position;  \n"
                + "    v_texCoord = a_texCoord;               \n"
                + "}";
            this.shader = new cc.GLProgram();
            this.shader.initWithVertexShaderByteArray(DEFAULT_VERTEX_SHADER, MULTI_TEXTURES_FRAGMENT_SHADER);
            this.shader.addAttribute(cc.ATTRIBUTE_NAME_POSITION, cc.VERTEX_ATTRIB_POSITION);
            this.shader.addAttribute(cc.ATTRIBUTE_NAME_TEX_COORD, cc.VERTEX_ATTRIB_TEX_COORDS);
            this.shader.link();
            this.shader.updateUniforms();   //绑定位置，这个是cocos封装后必须做的事。详细可以看代码
            this.initGL();
            var p = this.shader.getProgram();
            this.tex1Location = gl.getUniformLocation(p, "CC_Texture0");    //如果frag shader最终没有用某个uniform，该uniform会被优化删掉
            this.tex2Location = gl.getUniformLocation(p, "CC_Texture1");
            trace(this.tex1Location, this.tex2Location);
            glnode.draw = function() {
                this.shader.use();                      //使用这个shader来绘制，封装了gl的use。跟指定glnode.shaderProgram类似
                this.shader.setUniformsForBuiltins();   //设置坐标系变换
                gl.activeTexture(gl.TEXTURE0);          //webgl中一共32个，可以看cocos2d列的常量
                gl.bindTexture(gl.TEXTURE_2D, this.tex1.getName());
                gl.uniform1i(this.tex1Location, 0);     //把CC_Texture0指向gl.TEXTURE0
                gl.activeTexture(gl.TEXTURE1);
                gl.bindTexture(gl.TEXTURE_2D, this.tex2.getName());
                gl.uniform1i(this.tex2Location, 1);
                cc.glEnableVertexAttribs( cc.VERTEX_ATTRIB_FLAG_TEX_COORDS | cc.VERTEX_ATTRIB_FLAG_POSITION);   //实际对gl的api做了封装，增加了这两个属性的位置映射。用于vertexAttribPointer
                // Draw fullscreen Square
                gl.bindBuffer(gl.ARRAY_BUFFER, this.squareVertexPositionBuffer);
                gl.vertexAttribPointer(cc.VERTEX_ATTRIB_POSITION, 2, gl.FLOAT, false, 0, 0);
                gl.bindBuffer(gl.ARRAY_BUFFER, this.squareVertexTextureBuffer);
                gl.vertexAttribPointer(cc.VERTEX_ATTRIB_TEX_COORDS, 2, gl.FLOAT, false, 0, 0);
                gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
                gl.activeTexture(gl.TEXTURE0);
                gl.bindTexture(gl.TEXTURE_2D, null);
                gl.activeTexture(gl.TEXTURE1);
                gl.bindTexture(gl.TEXTURE_2D, null);        //使用完必须置为空，否则影响其他node
                gl.bindBuffer(gl.ARRAY_BUFFER, null);
            }.bind(this);
        }
    },
    initGL:function() {
        var tex1 = cc.textureCache.addImage("res2/item_2.png");
        var tex2 = cc.textureCache.addImage("res2/item_3.png");
        this.tex1 = tex1;
        this.tex2 = tex2;
        //
        // Square
        //
        var squareVertexPositionBuffer = this.squareVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
        var vertices = [
            128,  128,
            0,    128,
            128,  0,
            0,    0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        var squareVertexTextureBuffer = this.squareVertexTextureBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexTextureBuffer);
        var texcoords = [
            0, 0,
            1, 0,
            0, 1,
            1, 1
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(texcoords), gl.STATIC_DRAW);
        gl.bindBuffer(gl.ARRAY_BUFFER, null);
    }
});

2014.11.07 补充：

由于3.1版本关于坐标系的计算发生了改变，上述例子不会正常显示。

 

需要扩展cc.Node为cc.GLNode。

 

cc.GLNode = cc.GLNode || cc.Node.extend({
    ctor:function(){
        this._super();
        this.init();
    },
    _initRendererCmd:function(){
        this._rendererCmd = new cc.CustomRenderCmdWebGL(this, function(){
            cc.kmGLMatrixMode(cc.KM_GL_MODELVIEW);
            cc.kmGLPushMatrix();
            cc.kmGLLoadMatrix(this._stackMatrix);

            this.draw();

            cc.kmGLPopMatrix();
        });
    }
});

另外，在new cc.GLProgram后retain一下就可以兼容jsb了（cocos2d-js 3.1后）