WebGL 示例代码:画一个三角形
WebGL 实例代码:画一个三角形
本小节演示如何在WebGL中绘制三角形。
<!doctype html> <html> <body> <canvas width = "570" height = "570" id = "my_Canvas"></canvas> <script> /*============== Creating a canvas ====================*/ var canvas = document.getElementById('my_Canvas'); gl = canvas.getContext('experimental-webgl'); /*======== Defining and storing the geometry ===========*/ var vertices = [ -0.5,0.5,0.0, -0.5,-0.5,0.0, 0.5,-0.5,0.0, ]; indices = [0,1,2]; // Create an empty buffer object to store vertex buffer var vertex_buffer = gl.createBuffer(); // Bind appropriate array buffer to it gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer); // Pass the vertex data to the buffer gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW); // Unbind the buffer gl.bindBuffer(gl.ARRAY_BUFFER, null); // Create an empty buffer object to store Index buffer var Index_Buffer = gl.createBuffer(); // Bind appropriate array buffer to it gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, Index_Buffer); // Pass the vertex data to the buffer gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW); // Unbind the buffer gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null); /*================ Shaders ====================*/ // Vertex shader source code var vertCode = 'attribute vec3 coordinates;' + 'void main(void) {' + ' gl_Position = vec4(coordinates, 1.0);' + '}'; // Create a vertex shader object var vertShader = gl.createShader(gl.VERTEX_SHADER); // Attach vertex shader source code gl.shaderSource(vertShader, vertCode); // Compile the vertex shader gl.compileShader(vertShader); //fragment shader source code var fragCode = 'void main(void) {' + ' gl_FragColor = vec4(0.0, 0.0, 0.0, 0.1);' + '}'; // Create fragment shader object var fragShader = gl.createShader(gl.FRAGMENT_SHADER); // Attach fragment shader source code gl.shaderSource(fragShader, fragCode); // Compile the fragmentt shader gl.compileShader(fragShader); // Create a shader program object to store // the combined shader program var shaderProgram = gl.createProgram(); // Attach a vertex shader gl.attachShader(shaderProgram, vertShader); // Attach a fragment shader gl.attachShader(shaderProgram, fragShader); // Link both the programs gl.linkProgram(shaderProgram); // Use the combined shader program object gl.useProgram(shaderProgram); /*======= Associating shaders to buffer objects =======*/ // Bind vertex buffer object gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer); // Bind index buffer object gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, Index_Buffer); // Get the attribute location var coord = gl.getAttribLocation(shaderProgram, "coordinates"); // Point an attribute to the currently bound VBO gl.vertexAttribPointer(coord, 3, gl.FLOAT, false, 0, 0); // Enable the attribute gl.enableVertexAttribArray(coord); /*=========Drawing the triangle===========*/ // Clear the canvas gl.clearColor(0.5, 0.5, 0.5, 0.9); // Enable the depth test gl.enable(gl.DEPTH_TEST); // Clear the color buffer bit gl.clear(gl.COLOR_BUFFER_BIT); // Set the view port gl.viewport(0,0,canvas.width,canvas.height); // Draw the triangle gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT,0); </script> </body> </html>