WebGL - Introduction

xholonWorkbook.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--Xholon Workbook http://www.primordion.com/Xholon/gwt/ MIT License, Copyright (C) Ken Webb, Wed May 27 2020 15:01:45 GMT-0400 (Eastern Daylight Time)-->
<XholonWorkbook>

<Notes><![CDATA[
Xholon
------
Title: WebGL - Introduction
Description: 
Url: http://www.primordion.com/Xholon/gwt/
InternalName: 0e25100dffaa5432f8fc471b22f93da9
Keywords: 

My Notes
--------
May 27, 2020

http://127.0.0.1:8080/war/Xholon.html?app=WebGL+-+Introduction&src=lstr&gui=clsc&jslib=gl-matrix

TODO
----
- Tutorial05behavior runs veeerrrryyyyyy slowlyyyyyyyyyyyyyyyyyyyyy (Firefox, nodejs http-server, localhost)


References
----------
(1) https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API

(2) https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial

(3) https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial/Getting_started_with_WebGL

(4) https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial/Adding_2D_content_to_a_WebGL_context

(5) https://mdn.github.io/webgl-examples/tutorial/gl-matrix.js
    Tutorial 2 (and maybe others) require this JavaScript library

(6) https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial/Creating_3D_objects_using_WebGL

]]></Notes>  

<_-.XholonClass>
  <PhysicalSystem/>
  
  <Tutorial>
    <!--<Tutorial01/>
    <Tutorial02/>-->
    <Tutorial05/>
  </Tutorial>
  
</_-.XholonClass>

<xholonClassDetails>
  
</xholonClassDetails>

<PhysicalSystem>
  <!--<Tutorial01/>-->
  <!--<Tutorial02/>-->
  <Tutorial05/>
</PhysicalSystem>

<Tutorial01behavior implName="org.primordion.xholon.base.Behavior_gwtjs"><![CDATA[/*
  // see: Getting_started_with_WebGL[ref 3]
  const xhcanvas = $doc.querySelector("#xhcanvas");
  xhcanvas.innerHTML = '<canvas id="canvas01"' + '></canvas>';
  const canvas = xhcanvas.firstElementChild;
  // Initialize the GL context
  const gl = canvas.getContext("webgl");

  // Only continue if WebGL is available and working
  if (gl === null) {
    alert("Unable to initialize WebGL. Your browser or machine may not support it.");
  }
  else {
    // Set clear color to black, fully opaque
    gl.clearColor(0.0, 0.0, 0.0, 1.0);
    // Clear the color buffer with specified clear color
    gl.clear(gl.COLOR_BUFFER_BIT);
  }
//# sourceURL=Tutorial01behavior.js
*/]]></Tutorial01behavior>

<Tutorial02behavior implName="org.primordion.xholon.base.Behavior_gwtjs"><![CDATA[/*
  // see: Adding_2D_content_to_a_WebGL_context[ref 4]
  const xhcanvas = $doc.querySelector("#xhcanvas");
  xhcanvas.innerHTML = '<canvas id="canvas02"' + '></canvas>';
  const canvas = xhcanvas.firstElementChild;
  // Initialize the GL context
  const gl = canvas.getContext("webgl");

  // Vertex shader program

  const vsSource = `
    attribute vec4 aVertexPosition;
    uniform mat4 uModelViewMatrix;
    uniform mat4 uProjectionMatrix;
    void main() {
      gl_Position = uProjectionMatrix * uModelViewMatrix * aVertexPosition;
    }
  `;

  // Fragment shader program

  const fsSource = `
    void main() {
      gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
    }
  `;

  // Initialize a shader program; this is where all the lighting
  // for the vertices and so forth is established.
  const shaderProgram = initShaderProgram(gl, vsSource, fsSource);

  // Collect all the info needed to use the shader program.
  // Look up which attribute our shader program is using
  // for aVertexPosition and look up uniform locations.
  const programInfo = {
    program: shaderProgram,
    attribLocations: {
      vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
    },
    uniformLocations: {
      projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
      modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
    },
  };

  // Here's where we call the routine that builds all the
  // objects we'll be drawing.
  const buffers = initBuffers(gl);

  // Draw the scene
  //drawScene(gl, programInfo, buffers); // moved to Xholon beh act()

//
// initBuffers
//
// Initialize the buffers we'll need. For this demo, we just
// have one object -- a simple two-dimensional square.
//
function initBuffers(gl) {

  // Create a buffer for the square's positions.

  const positionBuffer = gl.createBuffer();

  // Select the positionBuffer as the one to apply buffer
  // operations to from here out.

  gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);

  // Now create an array of positions for the square.

  const positions = [
     1.0,  1.0,
    -1.0,  1.0,
     1.0, -1.0,
    -1.0, -1.0,
  ];

  // Now pass the list of positions into WebGL to build the
  // shape. We do this by creating a Float32Array from the
  // JavaScript array, then use it to fill the current buffer.

  gl.bufferData(gl.ARRAY_BUFFER,
                new Float32Array(positions),
                gl.STATIC_DRAW);

  return {
    position: positionBuffer,
  };
}

//
// Draw the scene.
//
function drawScene(gl, programInfo, buffers) {
  gl.clearColor(0.0, 0.0, 0.0, 1.0);  // Clear to black, fully opaque
  gl.clearDepth(1.0);                 // Clear everything
  gl.enable(gl.DEPTH_TEST);           // Enable depth testing
  gl.depthFunc(gl.LEQUAL);            // Near things obscure far things

  // Clear the canvas before we start drawing on it.

  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

  // Create a perspective matrix, a special matrix that is
  // used to simulate the distortion of perspective in a camera.
  // Our field of view is 45 degrees, with a width/height
  // ratio that matches the display size of the canvas
  // and we only want to see objects between 0.1 units
  // and 100 units away from the camera.

  const fieldOfView = 45 * Math.PI / 180;   // in radians
  const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
  const zNear = 0.1;
  const zFar = 100.0;
  const projectionMatrix = $wnd.mat4.create();

  // note: glmatrix.js always has the first argument
  // as the destination to receive the result.
  $wnd.mat4.perspective(projectionMatrix,
                   fieldOfView,
                   aspect,
                   zNear,
                   zFar);

  // Set the drawing position to the "identity" point, which is
  // the center of the scene.
  const modelViewMatrix = $wnd.mat4.create();

  // Now move the drawing position a bit to where we want to
  // start drawing the square.

  $wnd.mat4.translate(modelViewMatrix,     // destination matrix
                 modelViewMatrix,     // matrix to translate
                 [-0.0, 0.0, -6.0]);  // amount to translate

  // Tell WebGL how to pull out the positions from the position
  // buffer into the vertexPosition attribute.
  {
    const numComponents = 2;
    const type = gl.FLOAT;
    const normalize = false;
    const stride = 0;
    const offset = 0;
    gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
    gl.vertexAttribPointer(
        programInfo.attribLocations.vertexPosition,
        numComponents,
        type,
        normalize,
        stride,
        offset);
    gl.enableVertexAttribArray(
        programInfo.attribLocations.vertexPosition);
  }

  // Tell WebGL to use our program when drawing

  gl.useProgram(programInfo.program);

  // Set the shader uniforms

  gl.uniformMatrix4fv(
      programInfo.uniformLocations.projectionMatrix,
      false,
      projectionMatrix);
  gl.uniformMatrix4fv(
      programInfo.uniformLocations.modelViewMatrix,
      false,
      modelViewMatrix);

  {
    const offset = 0;
    const vertexCount = 4;
    gl.drawArrays(gl.TRIANGLE_STRIP, offset, vertexCount);
  }
}

//
// Initialize a shader program, so WebGL knows how to draw our data
//
function initShaderProgram(gl, vsSource, fsSource) {
  const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
  const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);

  // Create the shader program

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

  // If creating the shader program failed, alert

  if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
    alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram));
    return null;
  }

  return shaderProgram;
}

//
// creates a shader of the given type, uploads the source and
// compiles it.
//
function loadShader(gl, type, source) {
  const shader = gl.createShader(type);

  // Send the source to the shader object

  gl.shaderSource(shader, source);

  // Compile the shader program

  gl.compileShader(shader);

  // See if it compiled successfully

  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
    alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));
    gl.deleteShader(shader);
    return null;
  }

  return shader;
}

var me, beh = {
  postConfigure: function() {
    me = this.cnode.parent();
  },
  act: function() {
    drawScene(gl, programInfo, buffers);
  }
}
//# sourceURL=Tutorial02behavior.js
*/]]></Tutorial02behavior>

<Tutorial05behavior implName="org.primordion.xholon.base.Behavior_gwtjs"><![CDATA[
  // see: [ref 6]
  const xhcanvas = $doc.querySelector("#xhcanvas");
  xhcanvas.innerHTML = '<canvas id="canvas05" width="640" height="480"' + '></canvas>';
  const canvas = xhcanvas.firstElementChild;
  // Initialize the GL context
  const gl = canvas.getContext("webgl");
  
  $wnd.xh.css.style(`
canvas {
	border: 2px solid black;
	background-color: black;
}
video {
	display: none;
}
`);

var cubeRotation = 0.0;

//
// Start here
//
function main() {

  // Vertex shader program

  const vsSource = `
    attribute vec4 aVertexPosition;
    attribute vec4 aVertexColor;

    uniform mat4 uModelViewMatrix;
    uniform mat4 uProjectionMatrix;

    varying lowp vec4 vColor;

    void main(void) {
      gl_Position = uProjectionMatrix * uModelViewMatrix * aVertexPosition;
      vColor = aVertexColor;
    }
  `;

  // Fragment shader program

  const fsSource = `
    varying lowp vec4 vColor;

    void main(void) {
      gl_FragColor = vColor;
    }
  `;

  // Initialize a shader program; this is where all the lighting
  // for the vertices and so forth is established.
  const shaderProgram = initShaderProgram(gl, vsSource, fsSource);

  // Collect all the info needed to use the shader program.
  // Look up which attributes our shader program is using
  // for aVertexPosition, aVevrtexColor and also
  // look up uniform locations.
  const programInfo = {
    program: shaderProgram,
    attribLocations: {
      vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
      vertexColor: gl.getAttribLocation(shaderProgram, 'aVertexColor'),
    },
    uniformLocations: {
      projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
      modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
    },
  };

  // Here's where we call the routine that builds all the
  // objects we'll be drawing.
  const buffers = initBuffers(gl);

  var then = 0;

  // Draw the scene repeatedly
  function render(now) {
    now *= 0.001;  // convert to seconds
    const deltaTime = now - then;
    then = now;

    drawScene(gl, programInfo, buffers, deltaTime);

    requestAnimationFrame(render);
  }
  requestAnimationFrame(render);
}

//
// initBuffers
//
// Initialize the buffers we'll need. For this demo, we just
// have one object -- a simple three-dimensional cube.
//
function initBuffers(gl) {

  // Create a buffer for the cube's vertex positions.

  const positionBuffer = gl.createBuffer();

  // Select the positionBuffer as the one to apply buffer
  // operations to from here out.

  gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);

  // Now create an array of positions for the cube.

  const positions = [
    // 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,
  ];

  // Now pass the list of positions into WebGL to build the
  // shape. We do this by creating a Float32Array from the
  // JavaScript array, then use it to fill the current buffer.

  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);

  // Now set up the colors for the faces. We'll use solid colors
  // for each face.

  const faceColors = [
    [1.0,  1.0,  1.0,  1.0],    // Front face: white
    [1.0,  0.0,  0.0,  1.0],    // Back face: red
    [0.0,  1.0,  0.0,  1.0],    // Top face: green
    [0.0,  0.0,  1.0,  1.0],    // Bottom face: blue
    [1.0,  1.0,  0.0,  1.0],    // Right face: yellow
    [1.0,  0.0,  1.0,  1.0],    // Left face: purple
  ];

  // Convert the array of colors into a table for all the vertices.

  var colors = [];

  for (var j = 0; j < faceColors.length; ++j) {
    const c = faceColors[j];

    // Repeat each color four times for the four vertices of the face
    colors = colors.concat(c, c, c, c);
  }

  const colorBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);

  // Build the element array buffer; this specifies the indices
  // into the vertex arrays for each face's vertices.

  const indexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);

  // This array defines each face as two triangles, using the
  // indices into the vertex array to specify each triangle's
  // position.

  const indices = [
    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
  ];

  // Now send the element array to GL

  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,
      new Uint16Array(indices), gl.STATIC_DRAW);

  return {
    position: positionBuffer,
    color: colorBuffer,
    indices: indexBuffer,
  };
}

//
// Draw the scene.
//
function drawScene(gl, programInfo, buffers, deltaTime) {
  gl.clearColor(0.0, 0.0, 0.0, 1.0);  // Clear to black, fully opaque
  gl.clearDepth(1.0);                 // Clear everything
  gl.enable(gl.DEPTH_TEST);           // Enable depth testing
  gl.depthFunc(gl.LEQUAL);            // Near things obscure far things

  // Clear the canvas before we start drawing on it.

  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

  // Create a perspective matrix, a special matrix that is
  // used to simulate the distortion of perspective in a camera.
  // Our field of view is 45 degrees, with a width/height
  // ratio that matches the display size of the canvas
  // and we only want to see objects between 0.1 units
  // and 100 units away from the camera.

  const fieldOfView = 45 * Math.PI / 180;   // in radians
  const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
  const zNear = 0.1;
  const zFar = 100.0;
  const projectionMatrix = $wnd.mat4.create();

  // note: glmatrix.js always has the first argument
  // as the destination to receive the result.
  $wnd.mat4.perspective(projectionMatrix,
                   fieldOfView,
                   aspect,
                   zNear,
                   zFar);

  // Set the drawing position to the "identity" point, which is
  // the center of the scene.
  const modelViewMatrix = $wnd.mat4.create();

  // Now move the drawing position a bit to where we want to
  // start drawing the square.

  $wnd.mat4.translate(modelViewMatrix,     // destination matrix
                 modelViewMatrix,     // matrix to translate
                 [-0.0, 0.0, -6.0]);  // amount to translate
  $wnd.mat4.rotate(modelViewMatrix,  // destination matrix
              modelViewMatrix,  // matrix to rotate
              cubeRotation,     // amount to rotate in radians
              [0, 0, 1]);       // axis to rotate around (Z)
  $wnd.mat4.rotate(modelViewMatrix,  // destination matrix
              modelViewMatrix,  // matrix to rotate
              cubeRotation * .7,// amount to rotate in radians
              [0, 1, 0]);       // axis to rotate around (X)

  // Tell WebGL how to pull out the positions from the position
  // buffer into the vertexPosition attribute
  {
    const numComponents = 3;
    const type = gl.FLOAT;
    const normalize = false;
    const stride = 0;
    const offset = 0;
    gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
    gl.vertexAttribPointer(
        programInfo.attribLocations.vertexPosition,
        numComponents,
        type,
        normalize,
        stride,
        offset);
    gl.enableVertexAttribArray(
        programInfo.attribLocations.vertexPosition);
  }

  // Tell WebGL how to pull out the colors from the color buffer
  // into the vertexColor attribute.
  {
    const numComponents = 4;
    const type = gl.FLOAT;
    const normalize = false;
    const stride = 0;
    const offset = 0;
    gl.bindBuffer(gl.ARRAY_BUFFER, buffers.color);
    gl.vertexAttribPointer(
        programInfo.attribLocations.vertexColor,
        numComponents,
        type,
        normalize,
        stride,
        offset);
    gl.enableVertexAttribArray(
        programInfo.attribLocations.vertexColor);
  }

  // Tell WebGL which indices to use to index the vertices
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffers.indices);

  // Tell WebGL to use our program when drawing

  gl.useProgram(programInfo.program);

  // Set the shader uniforms

  gl.uniformMatrix4fv(
      programInfo.uniformLocations.projectionMatrix,
      false,
      projectionMatrix);
  gl.uniformMatrix4fv(
      programInfo.uniformLocations.modelViewMatrix,
      false,
      modelViewMatrix);

  {
    const vertexCount = 36;
    const type = gl.UNSIGNED_SHORT;
    const offset = 0;
    gl.drawElements(gl.TRIANGLES, vertexCount, type, offset);
  }

  // Update the rotation for the next draw

  cubeRotation += deltaTime;
}

//
// Initialize a shader program, so WebGL knows how to draw our data
//
function initShaderProgram(gl, vsSource, fsSource) {
  const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
  const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);

  // Create the shader program

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

  // If creating the shader program failed, alert

  if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
    alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram));
    return null;
  }

  return shaderProgram;
}

//
// creates a shader of the given type, uploads the source and
// compiles it.
//
function loadShader(gl, type, source) {
  const shader = gl.createShader(type);

  // Send the source to the shader object

  gl.shaderSource(shader, source);

  // Compile the shader program

  gl.compileShader(shader);

  // See if it compiled successfully

  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
    alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));
    gl.deleteShader(shader);
    return null;
  }

  return shader;
}

var me, beh = {
  postConfigure: function() {
    me = this.cnode.parent();
  },
  act: function() {
    main();
  }
}
//# sourceURL=Tutorial05behavior.js
]]></Tutorial05behavior>

<SvgClient><Attribute_String roleName="svgUri"><![CDATA[data:image/svg+xml,
<svg width="100" height="50" xmlns="http://www.w3.org/2000/svg">
  <g>
    <title>Tutorial01</title>
    <rect id="PhysicalSystem/Tutorial01" fill="#98FB98" height="50" width="50" x="25" y="0"/>
    <g>
      <title>Height</title>
      <rect id="PhysicalSystem/Tutorial01/*" fill="#6AB06A" height="50" width="10" x="80" y="0"/>
    </g>
  </g>
</svg>
]]></Attribute_String><Attribute_String roleName="setup">${MODELNAME_DEFAULT},${SVGURI_DEFAULT}</Attribute_String></SvgClient>

</XholonWorkbook>