framebuffer.js Example File

framebuffer/qml/framebuffer/framebuffer.js
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Qt.include("gl-matrix.js")

//
// Draws a cube that has the Qt logo as decal texture on each face in to a texture.
// That texture is used as the texture for drawing another cube on the screen.
//

var gl;

var rttFramebuffer;
var rttTexture;
var rttWidth = 512;
var rttHeight = 512;

var cubeTexture = 0;

var vertexPositionAttribute;
var textureCoordAttribute;
var vertexNormalAttribute;
var vertexColorAttribute;
var mvMatrix = mat4.create();
var pMatrix  = mat4.create();
var nMatrix  = mat4.create();
var pMatrixUniform;
var mvMatrixUniform;
var nUniform;

var canvas3d;
var isLogEnabled = false;

function log(message) {
    if (isLogEnabled)
        console.log(message)
}

function initializeGL(canvas, textureLoader) {
    canvas3d = canvas
    try {
        // Get the OpenGL context object that represents the API we call
        gl = canvas.getContext("canvas3d", {depth:true, antialias:true, alpha:false});

        // Setup the OpenGL state
        gl.enable(gl.DEPTH_TEST);
        gl.enable(gl.CULL_FACE);
        gl.cullFace(gl.BACK);
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);

        // Initialize the shader program
        initShaders();

        // Initialize vertex and color buffers
        initBuffers();

        // Load the Qt logo as texture
        var qtLogoImage = TextureImageFactory.newTexImage();
        qtLogoImage.imageLoaded.connect(function() {
            cubeTexture = gl.createTexture();
            cubeTexture.name = "CubeTexture";
            gl.bindTexture(gl.TEXTURE_2D, cubeTexture);
            gl.texImage2D(gl.TEXTURE_2D,    // target
                          0,                // level
                          gl.RGBA,          // internalformat
                          gl.RGBA,          // format
                          gl.UNSIGNED_BYTE, // type
                          qtLogoImage);    // pixels

            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
            gl.generateMipmap(gl.TEXTURE_2D);
        });
        qtLogoImage.imageLoadingFailed.connect(function() {
            console.log("Texture load FAILED, "+qtLogoImage.errorString);
        });
        qtLogoImage.src = "qrc:/qtlogo.png";

        // Create the framebuffer object
        rttFramebuffer = gl.createFramebuffer();
        rttFramebuffer.name = "OffscreenRenderTarget";
        gl.bindFramebuffer(gl.FRAMEBUFFER, rttFramebuffer);

        // Create the texture
        rttTexture = gl.createTexture();
        rttTexture.name = "OffscreenRenderTargetTexture";
        gl.bindTexture(gl.TEXTURE_2D, rttTexture);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
        gl.texImage2D(gl.TEXTURE_2D, 0,
                      gl.RGBA, rttWidth, rttHeight,
                      0, gl.RGBA, gl.UNSIGNED_BYTE,
                      null);
        gl.generateMipmap(gl.TEXTURE_2D);

        // Bind the texture as color attachment, create and bind a depth buffer
        gl.framebufferTexture2D(gl.FRAMEBUFFER,
                                gl.COLOR_ATTACHMENT0,
                                gl.TEXTURE_2D, rttTexture, 0);
        var renderbuffer = gl.createRenderbuffer();
        gl.bindRenderbuffer(gl.RENDERBUFFER, renderbuffer);
        gl.renderbufferStorage(gl.RENDERBUFFER,
                               gl.DEPTH_COMPONENT16,
                               rttWidth, rttHeight);
        gl.framebufferRenderbuffer(gl.FRAMEBUFFER,
                                   gl.DEPTH_ATTACHMENT,
                                   gl.RENDERBUFFER, renderbuffer);
        gl.bindTexture(gl.TEXTURE_2D, 0);
        gl.bindRenderbuffer(gl.RENDERBUFFER, 0);
        gl.bindFramebuffer(gl.FRAMEBUFFER, 0);
    } catch(e) {
        console.log("initializeGL FAILURE!");
        console.log(""+e);
        console.log(""+e.message);
    }
}

function degToRad(degrees) {
    return degrees * Math.PI / 180;
}

function paintGL(canvas) {
    // bind the FBO and setup viewport
    gl.bindFramebuffer(gl.FRAMEBUFFER, rttFramebuffer);
    gl.viewport(0, 0, rttWidth, rttHeight);

    gl.clearColor(0.95, 0.95, 0.95, 1.0);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // Bind the loaded texture
    gl.bindTexture(gl.TEXTURE_2D, cubeTexture);

    // Calculate and set matrix uniforms
    mat4.perspective(pMatrix, degToRad(45), rttWidth / rttHeight, 0.1, 100.0);
    gl.uniformMatrix4fv(pMatrixUniform, false, pMatrix);

    mat4.identity(mvMatrix);
    mat4.translate(mvMatrix, mvMatrix, [0, 0, -5.0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.xRotSlider), [0, 1, 0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.yRotSlider), [1, 0, 0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.zRotSlider), [0, 0, 1]);
    gl.uniformMatrix4fv(mvMatrixUniform, false, mvMatrix);

    mat4.invert(nMatrix, mvMatrix);
    mat4.transpose(nMatrix, nMatrix);
    gl.uniformMatrix4fv(nUniform, false, nMatrix);

    // Draw the cube to the FBO
    gl.drawElements(gl.TRIANGLES, 36, gl.UNSIGNED_SHORT, 0);

    // Bind the render-to-texture and generate mipmaps
    gl.bindTexture(gl.TEXTURE_2D, rttTexture);
    gl.generateMipmap(gl.TEXTURE_2D);

    // Bind default framebuffer and setup viewport accordingly
    gl.bindFramebuffer(gl.FRAMEBUFFER, 0);
    gl.viewport(0, 0,
                canvas.width * canvas.devicePixelRatio,
                canvas.height * canvas.devicePixelRatio);
    gl.clearColor(0.98, 0.98, 0.98, 1.0);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // Calculate and set matrix uniforms
    mat4.perspective(pMatrix, degToRad(45), canvas.width / canvas.height, 0.1, 100.0);
    gl.uniformMatrix4fv(pMatrixUniform, false, pMatrix);

    mat4.identity(mvMatrix);
    mat4.translate(mvMatrix, mvMatrix, [(canvas.yRotAnim - 120.0) / 120.0,
                                        (canvas.xRotAnim -  60.0) / 50.0,
                                        -10.0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.xRotAnim), [0, 1, 0]);
    gl.uniformMatrix4fv(mvMatrixUniform, false, mvMatrix);

    mat4.invert(nMatrix, mvMatrix);
    mat4.transpose(nMatrix, nMatrix);
    gl.uniformMatrix4fv(nUniform, false, nMatrix);

    // Draw the on-screen cube
    gl.drawElements(gl.TRIANGLES, 36, gl.UNSIGNED_SHORT, 0);
}

function resizeGL(canvas)
{
    var pixelRatio = canvas.devicePixelRatio;
    canvas.pixelSize = Qt.size(canvas.width * pixelRatio,
                               canvas.height * pixelRatio);
}

function initBuffers()
{
    log("        cubeVertexPositionBuffer");
    var cubeVertexPositionBuffer = gl.createBuffer();
    cubeVertexPositionBuffer.name = "cubeVertexPositionBuffer";
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
    gl.bufferData(
                gl.ARRAY_BUFFER,
                new Float32Array([// Front face
                                        -1.0, -1.0,  1.0,
                                        1.0, -1.0,  1.0,
                                        1.0,  1.0,  1.0,
                                        -1.0,  1.0,  1.0,

                                        // Back face
                                        -1.0, -1.0, -1.0,
                                        -1.0,  1.0, -1.0,
                                        1.0,  1.0, -1.0,
                                        1.0, -1.0, -1.0,

                                        // Top face
                                        -1.0,  1.0, -1.0,
                                        -1.0,  1.0,  1.0,
                                        1.0,  1.0,  1.0,
                                        1.0,  1.0, -1.0,

                                        // Bottom face
                                        -1.0, -1.0, -1.0,
                                        1.0, -1.0, -1.0,
                                        1.0, -1.0,  1.0,
                                        -1.0, -1.0,  1.0,

                                        // Right face
                                        1.0, -1.0, -1.0,
                                        1.0,  1.0, -1.0,
                                        1.0,  1.0,  1.0,
                                        1.0, -1.0,  1.0,

                                        // Left face
                                        -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);

    gl.enableVertexAttribArray(vertexPositionAttribute);
    gl.vertexAttribPointer(vertexPositionAttribute, 3, gl.FLOAT, false, 0, 0);

    log("        cubeVertexIndexBuffer");
    var cubeVertexIndexBuffer = gl.createBuffer();
    cubeVertexIndexBuffer.name = "cubeVertexIndexBuffer";
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,
                  new Uint16Array([
                                            0,  1,  2,      0,  2,  3,    // front
                                            4,  5,  6,      4,  6,  7,    // back
                                            8,  9,  10,     8,  10, 11,   // top
                                            12, 13, 14,     12, 14, 15,   // bottom
                                            16, 17, 18,     16, 18, 19,   // right
                                            20, 21, 22,     20, 22, 23    // left
                                        ]),
                  gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);

    log("        cubeVerticesTextureCoordBuffer");
    var cubeVerticesTextureCoordBuffer = gl.createBuffer();
    cubeVerticesTextureCoordBuffer.name = "cubeVerticesTextureCoordBuffer";
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesTextureCoordBuffer);
    var textureCoordinates = [
                // Front
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Back
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Top
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Bottom
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Right
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Left
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0
            ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoordinates),
                  gl.STATIC_DRAW);
    gl.enableVertexAttribArray(textureCoordAttribute);
    gl.vertexAttribPointer(textureCoordAttribute, 2, gl.FLOAT, false, 0, 0);

    var cubeVerticesNormalBuffer = gl.createBuffer();
    cubeVerticesNormalBuffer.name = "cubeVerticesNormalBuffer";
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesNormalBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
                                                              // Front
                                                              0.0,  0.0,  1.0,
                                                              0.0,  0.0,  1.0,
                                                              0.0,  0.0,  1.0,
                                                              0.0,  0.0,  1.0,

                                                              // Back
                                                              0.0,  0.0, -1.0,
                                                              0.0,  0.0, -1.0,
                                                              0.0,  0.0, -1.0,
                                                              0.0,  0.0, -1.0,

                                                              // Top
                                                              0.0,  1.0,  0.0,
                                                              0.0,  1.0,  0.0,
                                                              0.0,  1.0,  0.0,
                                                              0.0,  1.0,  0.0,

                                                              // Bottom
                                                              0.0, -1.0,  0.0,
                                                              0.0, -1.0,  0.0,
                                                              0.0, -1.0,  0.0,
                                                              0.0, -1.0,  0.0,

                                                              // Right
                                                              1.0,  0.0,  0.0,
                                                              1.0,  0.0,  0.0,
                                                              1.0,  0.0,  0.0,
                                                              1.0,  0.0,  0.0,

                                                              // Left
                                                              -1.0,  0.0,  0.0,
                                                              -1.0,  0.0,  0.0,
                                                              -1.0,  0.0,  0.0,
                                                              -1.0,  0.0,  0.0
                                                          ]), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesNormalBuffer);
    gl.vertexAttribPointer(vertexNormalAttribute, 3, gl.FLOAT, false, 0, 0);
}

function initShaders()
{
    var vertexShader = getShader(gl,
                                 "attribute highp vec3 aVertexNormal;   \
                                  attribute highp vec3 aVertexPosition; \
                                  attribute highp vec2 aTextureCoord;   \

                                  uniform highp mat4 uNormalMatrix;     \
                                  uniform mat4 uMVMatrix;               \
                                  uniform mat4 uPMatrix;                \

                                  varying mediump vec4 vColor;          \
                                  varying highp vec2 vTextureCoord;     \
                                  varying highp vec3 vLighting;         \

                                  void main(void) {                     \
                                      gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);                      \
                                      vTextureCoord = aTextureCoord;                                                        \
                                      highp vec3 ambientLight = vec3(0.5, 0.5, 0.5);                                        \
                                      highp vec3 directionalLightColor = vec3(0.75, 0.75, 0.75);                             \
                                      highp vec3 directionalVector = vec3(0.85, 0.8, 0.75);                                 \
                                      highp vec4 transformedNormal = uNormalMatrix * vec4(aVertexNormal, 1.0);              \
                                      highp float directional = max(dot(transformedNormal.xyz, directionalVector), 0.0);    \
                                      vLighting = ambientLight + (directionalLightColor * directional);                     \
                                  }", gl.VERTEX_SHADER);
    var fragmentShader = getShader(gl,
                                   "varying highp vec2 vTextureCoord;   \
                                    varying highp vec3 vLighting;       \

                                    uniform sampler2D uSampler;         \

                                    void main(void) {                   \
                                        mediump vec3 texelColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t)).rgb;  \
                                        gl_FragColor = vec4(texelColor * vLighting, 1.0);                                       \
                                    }", gl.FRAGMENT_SHADER);

    var shaderProgram = gl.createProgram();
    gl.attachShader(shaderProgram, vertexShader);
    gl.attachShader(shaderProgram, fragmentShader);
    gl.linkProgram(shaderProgram);

    if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
        console.log("Could not initialise shaders");
        console.log(gl.getProgramInfoLog(shaderProgram));
    }

    gl.useProgram(shaderProgram);

    // look up where the vertex data needs to go.
    vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
    gl.enableVertexAttribArray(vertexPositionAttribute);
    textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
    gl.enableVertexAttribArray(textureCoordAttribute);
    vertexNormalAttribute =gl.getAttribLocation(shaderProgram, "aVertexNormal");
    gl.enableVertexAttribArray(vertexNormalAttribute);

    pMatrixUniform  = gl.getUniformLocation(shaderProgram, "uPMatrix");
    mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
    nUniform = gl.getUniformLocation(shaderProgram, "uNormalMatrix");

    var textureSamplerUniform = gl.getUniformLocation(shaderProgram, "uSampler")
    gl.activeTexture(gl.TEXTURE0);
    gl.uniform1i(textureSamplerUniform, 0);
}

function getShader(gl, str, type) {
    var shader = gl.createShader(type);
    gl.shaderSource(shader, str);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        console.log("JS:Shader compile failed");
        console.log(gl.getShaderInfoLog(shader));
        return null;
    }

    return shader;
}

© 2016 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.