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原生WebGL绘制3个点

2017-07-13 15:26 281 查看

<html>
<body>
<canvas width = "300" height = "300" id = "my_Canvas"></canvas>
<script>
var canvas = document.getElementById('my_Canvas');
var gl = canvas.getContext('webgl');

var vertCode = 'attribute vec2 coordinates;' +
'void main(void) {' +
'gl_PointSize = 20.0;' +
'gl_Position = vec4(coordinates, 0.0, 1.0);' +
'}';
var vertShader = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vertShader, vertCode);
gl.compileShader(vertShader);

var fragCode = 'void main(void) {' +
'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);' +
'}';
var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fragShader, fragCode);
gl.compileShader(fragShader);

var shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertShader);
gl.attachShader(shaderProgram, fragShader);
gl.linkProgram(shaderProgram);
gl.useProgram(shaderProgram);

var vertexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
var vertexArray = [0.0, -0.5, 0.0, 0.5, 0.5, 0.0];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertexArray), gl.STATIC_DRAW);
var coord = gl.getAttribLocation(shaderProgram, "coordinates");
gl.vertexAttribPointer(coord, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(coord);
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.enable(gl.DEPTH_TEST);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.viewport(0, 0, canvas.width, canvas.height);
gl.drawArrays(gl.POINTS, 0, 3);
</script>
</body>
</html>

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