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| var VSHADER_SOURCE = 'attribute vec4 a_Position;\n' + 'attribute vec4 a_Color;\n' + 'varying vec4 v_Color;\n' + 'void main() {\n' + 'gl_Position = a_Position;\n' + 'gl_PointSize = 10.0;\n' + 'v_Color = a_Color;\n' + '}\n';
var FSHADER_SOURCE= 'precision mediump float;\n' + 'varying vec4 v_Color;\n' + 'void main(){\n'+ 'gl_FragColor = v_Color;\n'+ '}\n';
function main() {
var canvas = document.getElementById("webgl"); if (!canvas) { console.log("Failed to retrieve the <canvas> element"); return; }
var gl = getWebGLContext(canvas); if (!gl) { console.log("Failed to get the rendering context for WebGL"); return; }
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) { console.log("Failed to initialize shaders."); return; }
var n = initVertexBuffers(gl); if (n < 0) { console.log('Failed to set the positions of the vertices'); return; }
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.POINTS, 0, n); }
function initVertexBuffers(gl) { var verticesColors = new Float32Array( [0.0, 0.5, 1.0, 0.0, 0.0, -0.5, -0.5, 0.0, 1.0, 0.0, 0.5, -0.5, 0.0, 0.0, 1.0] ); var n=3;
var verteColorBuffer = gl.createBuffer(); gl.bindBuffer(gl.ARRAY_BUFFER, verteColorBuffer); gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW);
var FSIZE = verticesColors.BYTES_PER_ELEMENT;
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, FSIZE*5, 0); gl.enableVertexAttribArray(a_Position);
var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE*5, FSIZE*2); gl.enableVertexAttribArray(a_Color);
return n; }
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