4 <title>GPU Memory Test: Use N MB of GPU Memory with WebGL</title>
6 <script id="vertex-shader" type="x-shader/x-vertex">
7 attribute vec2 a_position;
8 varying vec2 v_position;
10 v_position = a_position;
11 gl_Position = vec4(a_position, 0, 1);
15 <script id="fragment-shader" type="x-shader/x-fragment">
16 precision mediump float;
17 uniform sampler2D u_image;
18 varying vec2 v_position;
20 gl_FragColor = texture2D(u_image, v_position);
26 var shaderProgram = null;
32 // Create n textures of about 1MB each.
33 function useGpuMemory(mb_to_use)
37 var canvas = document.getElementById("canvas_id");
38 gl = canvas.getContext("experimental-webgl");
40 throw "Unable to fetch WebGL rendering context for Canvas";
43 // Create n textures that are each about 1MB and FBOs to render to them.
44 for (var i = 0; i < n; ++i) {
45 var texture = gl.createTexture();
46 var fbo = gl.createFramebuffer();
47 textures.push(texture);
50 gl.bindTexture(gl.TEXTURE_2D, texture);
51 gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
52 gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
53 gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
54 gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
55 gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 512, 512, 0,
56 gl.RGBA, gl.UNSIGNED_BYTE, null)
58 gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
59 gl.framebufferTexture2D(gl.FRAMEBUFFER,
66 // Create a shader that samples a 2D image.
67 var vertexShader = gl.createShader(gl.VERTEX_SHADER);
68 gl.shaderSource(vertexShader,
69 document.getElementById("vertex-shader").textContent);
70 gl.compileShader(vertexShader);
72 var fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
73 gl.shaderSource(fragmentShader,
74 document.getElementById("fragment-shader").textContent);
75 gl.compileShader(fragmentShader);
77 shaderProgram = gl.createProgram();
78 gl.attachShader(shaderProgram, vertexShader);
79 gl.attachShader(shaderProgram, fragmentShader);
80 gl.linkProgram(shaderProgram);
81 gl.useProgram(shaderProgram);
83 // Bind a vertex buffer with a single triangle
84 var buffer = gl.createBuffer();
85 gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
86 var bufferData = new Float32Array([-1.0, -1.0, 1.0, -1.0, -1.0, 1.0]);
87 gl.bufferData(gl.ARRAY_BUFFER, bufferData, gl.STATIC_DRAW);
88 gl.enableVertexAttribArray(shaderProgram.a_position);
89 gl.vertexAttribPointer(shaderProgram.a_position, 2, gl.FLOAT, false, 0, 0);
91 // Signal back to the test runner that we're done allocating memory.
92 domAutomationController.send("DONE_USE_GPU_MEMORY");
94 // Start the event loop.
100 // Render a solid color to each texture.
101 for (var i = 0; i < n; ++i) {
102 gl.bindFramebuffer(gl.FRAMEBUFFER, fbos[i]);
103 gl.viewport(0, 0, 512, 512);
104 gl.clearColor(0.0, Math.sin(t/60.0)*0.25 + 0.75*(i+1.0)/n, 0.0, 1.0);
105 gl.clear(gl.COLOR_BUFFER_BIT);
108 // Draw these textures to the screen, offset by 1 pixel increments
109 gl.bindFramebuffer(gl.FRAMEBUFFER, null);
110 gl.viewport(0, 0, 256, 256);
111 gl.clearColor(0.0, 0.0, 0.0, 1.0);
112 gl.clear(gl.COLOR_BUFFER_BIT);
113 for (var i = 0; i < n; ++i) {
114 gl.viewport(i, i, 256-i, 256-i);
115 gl.activeTexture(gl.TEXTURE0);
116 gl.bindTexture(gl.TEXTURE_2D, textures[i]);
117 gl.uniform1i(shaderProgram.u_image, 0);
118 gl.drawArrays(gl.TRIANGLES, 0, 3);
126 window.webkitRequestAnimationFrame(tick);
133 <canvas id="canvas_id" width=256px height=256px style="width:256px; height:256px;"/>