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webgl.js
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webgl.js
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/** Compile the given shader and handle any errors that arise during compilation.
*
* @param {WebGLRenderingContext} gl
* @param {string} source
* @param type gl.VERTEX_SHADER or gl.FRAGMENT_SHADER
* @returns {WebGLShader}
*/
function compileShader(gl, source, type) {
var shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
var error = gl.getShaderInfoLog(shader);
gl.deleteShader(shader);
throw "Shader compile error\n" + error;
}
return shader;
}
/** Generate the GLSL program and attach it to the WebGL context
*
* 1. Generate the equation-specific GLSL and insert it into the shader template.
* 2. Compile, attach, link and use the shaders.
* 3. Reset time, mouse and keyboard values specific to an equation.
* 4. Delete the old program if necessary.
*
* @param {WebGLRenderingContext} gl
* @param {string} equation
* @returns {WebGLProgram}
*/
function setProgram(gl, equation) {
var prevProgram = gl.getParameter(gl.CURRENT_PROGRAM);
var vertexShaderSource = document.getElementById("vertex-shader").text;
var vertexShader = compileShader(gl, vertexShaderSource, gl.VERTEX_SHADER);
var glsl = generateGlsl(equation, settings.idleFunction);
var fragmentShaderSource = document.getElementById("fragment-shader").text;
fragmentShaderSource = fragmentShaderSource.replace(/%%method%%/g, settings.method.toUpperCase());
fragmentShaderSource = fragmentShaderSource.replace(/%%idle_function%%/g, glsl.idle);
fragmentShaderSource = fragmentShaderSource.replace(/%%f%%/g, glsl.f);
fragmentShaderSource = fragmentShaderSource.replace(/%%df%%/g, glsl.df);
if (settings.method !== "newton") {
fragmentShaderSource = fragmentShaderSource.replace(/%%ddf%%/g, glsl.ddf);
}
/* replace here */
var fragmentShader = compileShader(gl, fragmentShaderSource, gl.FRAGMENT_SHADER);
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
var error = gl.getProgramInfoLog(program);
gl.deleteProgram(program);
throw "Program link error\n" + error;
}
resetTime();
resetMouse();
settings.zoomFactor = 4.0;
gl.useProgram(program);
if (prevProgram) {
gl.deleteProgram(prevProgram);
}
return program;
}
/** Set up the geometry - a simple rectangle.
*
* @param {WebGLRenderingContext} gl
*/
function setGeometry(gl) {
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
-1.0, -1.0,
1.0, -1.0,
-1.0, 1.0,
-1.0, 1.0,
1.0, -1.0,
1.0, 1.0]),
gl.STATIC_DRAW
);
var program = gl.getParameter(gl.CURRENT_PROGRAM);
var positionLocation = gl.getAttribLocation(program, "a_position");
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
}
/** Initialize WebGL context, resize the canvas,
* setup the initial equation and start the rendering loop.
*
* @returns {WebGLRenderingContext} */
function initWebGL() {
var canvas = document.getElementById("newton");
var gl = canvas.getContext("webgl", {preserveDrawingBuffer: true});
if (!gl) {
gl = canvas.getContext("experimental-webgl", {preserveDrawingBuffer: true});
}
resizeCanvas(gl);
updateEquation(gl);
requestRender(gl);
return gl;
}
/** Request an animation frame and call the renderer when the browser is ready
* to process a new frame.
*
* I know people say not to setTimeout this, but it's helped with some implementations.
*
* @param {WebGLRenderingContext} gl
*/
function requestRender(gl) {
var render_callback = function (now) {
render(gl, now);
setTimeout(function () {
window.requestAnimationFrame(render_callback);
}, 2);
};
window.requestAnimationFrame(render_callback);
}
/** Resize the canvas to keep updated with window resizing, keeping in mind
* the device pixel ratio (2x and 3x displays).
*
* @param {WebGLRenderingContext} gl
*/
function resizeCanvas(gl) {
var devicePixelRatio = window.devicePixelRatio || 1;
var width = gl.canvas.clientWidth * devicePixelRatio;
var height = gl.canvas.clientHeight * devicePixelRatio;
if (width !== gl.canvas.width || height !== gl.canvas.height) {
gl.canvas.width = width;
gl.canvas.height = height;
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
}
}
/** Set the value of an uniform.
*
* @param {WebGLRenderingContext} gl
* @param {WebGLProgram} program
* @param {string} type
* @param {string} name
* @param value
*/
function setUniform(gl, program, type, name, value) {
var location = gl.getUniformLocation(program, name);
if (type === "1f") {
gl.uniform1f(location, value);
}
else if (type === "2f") {
gl.uniform2f(location, value[0], value[1]);
}
else if (type === "1i") {
gl.uniform1i(location, value);
}
}
/** Update the values of every uniform in the shader.
*
* @param {WebGLRenderingContext} gl
*/
function setUniforms(gl) {
var t = getTime();
var program = gl.getParameter(gl.CURRENT_PROGRAM);
setUniform(gl, program, "1f", "width", gl.canvas.width);
setUniform(gl, program, "1f", "height", gl.canvas.height);
setUniform(gl, program, "1f", "zoom_factor", settings.zoomFactor);
setUniform(gl, program, "1i", "mouse_idle", (mouseIdle) ? 1 : 0);
setUniform(gl, program, "2f", "t", [t, 0.0]);
setUniform(gl, program, "2f", "mouse", [mouseX * settings.zoomFactor, mouseY * settings.zoomFactor]);
setUniform(gl, program, "2f", "f", [touchForce, 0.0]);
}
/** Render a frame.
*
* 1. Clear the buffer.
* 2. Update the canvas size if the window was resized.
* 3. Set up the geometry.
* 4. Set the values of uniforms in the program.
* 5. Draw the rectangle.
* 6. Sync with gl.finish()
* 7. Update the controls display text.
* 8. Update the demo, if necessary.
*
* @param {WebGLRenderingContext} gl
*/
function render(gl) {
gl.clearColor(1.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
resizeCanvas(gl);
setGeometry(gl);
setUniforms(gl);
gl.drawArrays(gl.TRIANGLES, 0, 6);
gl.finish();
updateFPS();
updateDemo(gl);
}