创建纹理

directx3d_beginner

于 2019-10-10 16:15:58 发布

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分类专栏： webgl编程指南学习

本文链接：https://blog.csdn.net/directx3d_beginner/article/details/102484724

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<html>
<head>11</head>
<body>
<canvas id = "test" width = "500" height = "500">canvas </canvas>
<script >
//顶点着色器
var vertexShaderSource =
    'attribute vec4 a_Position;\n' +
    'attribute vec2 a_TexCoord;\n' +
   'varying vec2 v_TexCoord;\n' +    //varying变量
    'void main() {\n' +
    'gl_Position = a_Position;\n'+ //设置坐标
   'v_TexCoord = a_TexCoord;\n' + //将数据传给片元着色器
    '}\n';

//片元着色器
var fragmentShaderSource =
   '#ifdef GL_ES\n' +
    'precision mediump float;\n' +
   '#endif\n' +
   'uniform sampler2D u_Sampler;\n'+
   'varying vec2 v_TexCoord;\n' +    //varying变量
    'void main() {\n' +
    'gl_FragColor = texture2D(u_Sampler, v_TexCoord);\n'+ //设置颜色
    '}\n';

//创建着色器方法，输入参数：渲染上下文，着色器类型，数据源
function createShader(gl, type, source)
{
    //创建着色器对象
    var shader = gl.createShader(type);
    //提供数据源
    gl.shaderSource(shader,source);
    //编译着色器
    gl.compileShader(shader);
    //链接
    var success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
    if(success)
    {
        return shader;
    }
    console.log(gl.getShaderInfoLog(shader));
    gl.deleteShader(shader);

}
//将顶点着色器和像素着色器链接到一个着色程序
function createProgram(gl, vertexShader, fragmentShader)
{
    var program = gl.createProgram();
    gl.attachShader( program, vertexShader);
    gl.attachShader( program, fragmentShader);
    gl.linkProgram( program );
    var success = gl.getProgramParameter(program, gl.LINK_STATUS);
    if(success)
    {
        console.log("link right");
        return program;
    }
    console.log(gl.getProgramInfoLog(program));
    gl.deleteProgram(program);
}

function initVertexBuffers(gl)
{
   //顶点和纹理坐标
    var vertices = new Float32Array([
   -0.5, 0.5, 0.0, 1.0,
   -0.5, -0.5, 0.0,0.0,
   0.5, 0.5, 1.0,1.0,
   0.5, -0.5, 1.0,0.0,
   ]);

    //创建缓冲区对象
    var vertexBuffer = gl.createBuffer();
    //将缓冲区对象绑定到目标
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
    //向绑定的缓冲区对象中写入数据
    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

    var FSIZE = vertices.BYTES_PER_ELEMENT;
    //获取位置变量并传递顶点位置
    var thePosition = gl.getAttribLocation(program, 'a_Position');
    //将缓冲区对象分配给位置变量
    gl.vertexAttribPointer(thePosition, 2, gl.FLOAT, false, FSIZE * 4, 0 );
    //启动缓冲区
    gl.enableVertexAttribArray(thePosition);
    //纹理坐标
    var theTexCoord = gl.getAttribLocation(program, 'a_TexCoord');
    gl.vertexAttribPointer(theTexCoord, 2, gl.FLOAT, false, FSIZE * 4, FSIZE * 2 );
    gl.enableVertexAttribArray(theTexCoord);
}

function loadTexture(gl, n, texture, u_Sampler, image)
{
   //对纹理图像进行y轴翻转
   gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL,1);
   //开启0号纹理单元
   gl.activeTexture(gl.TEXTURE0);
   //向target绑定纹理对象
   gl.bindTexture(gl.TEXTURE_2D, texture);
   //配置纹理参数
   gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
   //配置纹理图像
   gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, image);
   //将0号纹理传递给着色器
   gl.uniform1i(u_Sampler, 0 );
       //绘制阶段

    gl.clear(gl.COLOR_BUFFER_BIT);

//绘制矩形
gl.drawArrays(gl.TRIANGLE_STRIP, 0, n);

}

    var vertexShader = createShader(gl,gl.VERTEX_SHADER,vertexShaderSource);
    var fragmentShader = createShader(gl,gl.FRAGMENT_SHADER, fragmentShaderSource);

    var program = createProgram(gl, vertexShader, fragmentShader);
    gl.useProgram(program);

    var numberVertices = 4;
   initVertexBuffers(gl);
//清除颜色
    gl.clearColor(0.0,0.0,0.0,1.0);
   initTextures(gl,numberVertices);

</script>
</body>
</html>