framebuffer.js Example File | Qt Canvas 3D (deprecated) 5.12.9

- Qt 5.12
- Qt Canvas 3D (deprecated)
- Framebuffer Example
- framebuffer.js Example File
- Qt 5.12.9 Reference Documentation

# framebuffer.js Example File

framebuffer/qml/framebuffer/framebuffer.js

     /****************************************************************************
     **
     ** Copyright (C) 2016 The Qt Company Ltd.
     ** Contact: https://www.qt.io/licensing/
     **
     ** This file is part of the QtCanvas3D module of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
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     ** accordance with the commercial license agreement provided with the
     ** Software or, alternatively, in accordance with the terms contained in
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     ** information use the contact form at https://www.qt.io/contact-us.
     **
     ** BSD License Usage
     ** Alternatively, you may use this file under the terms of the BSD license
     ** as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
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     **     from this software without specific prior written permission.
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     ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
     **
     ** $QT_END_LICENSE$
     **
     ****************************************************************************/

     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;
     }