Qt 5.9 | Qt Canvas 3D | Framebuffer Example | framebuffer.js Example File

Qt 5.9.2 Reference Documentation

# framebuffer.js Example File

framebuffer/qml/framebuffer/framebuffer.js

      /****************************************************************************
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      ** 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.
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      **
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      ** modification, are permitted provided that the following conditions are
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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;
      }