webgl/webgl-skybox-plus-environment-map.html

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<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - Textures - Skybox and Environment Map</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
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<body>
<div class="description">
Skybox using a cubemap.<br/>
</div>
<canvas id="canvas"></canvas>
</body>
<script id="envmap-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec3 a_normal;

uniform mat4 u_projection;
uniform mat4 u_view;
uniform mat4 u_world;

varying vec3 v_worldPosition;
varying vec3 v_worldNormal;

void main() {
  // Multiply the position by the matrix.
  gl_Position = u_projection * u_view * u_world * a_position;

  // send the view position to the fragment shader
  v_worldPosition = (u_world * a_position).xyz;

  // orient the normals and pass to the fragment shader
  v_worldNormal = mat3(u_world) * a_normal;
}
</script>
<!-- fragment shader -->
<script id="envmap-fragment-shader" type="x-shader/x-fragment">
precision highp float;

// Passed in from the vertex shader.
varying vec3 v_worldPosition;
varying vec3 v_worldNormal;

// The texture.
uniform samplerCube u_texture;

// The position of the camera
uniform vec3 u_worldCameraPosition;

void main() {
  vec3 worldNormal = normalize(v_worldNormal);
  vec3 eyeToSurfaceDir = normalize(v_worldPosition - u_worldCameraPosition);
  vec3 direction = reflect(eyeToSurfaceDir,worldNormal);

  gl_FragColor = textureCube(u_texture, direction);
}
</script>
<script id="skybox-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
varying vec4 v_position;
void main() {
  v_position = a_position;
  gl_Position = vec4(a_position.xy, 1, 1);
}
</script>
<script id="skybox-fragment-shader" type="x-shader/x-fragment">
precision mediump float;

uniform samplerCube u_skybox;
uniform mat4 u_viewDirectionProjectionInverse;

varying vec4 v_position;
void main() {
  vec4 t = u_viewDirectionProjectionInverse * v_position;
  gl_FragColor = textureCube(u_skybox, normalize(t.xyz / t.w));
}
</script>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
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and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
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<script src="resources/webgl-utils.js"></script>
<script src="resources/m4.js"></script>
<script src="resources/primitives.js"></script>
<script>
"use strict";

function main() {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  var canvas = document.querySelector("#canvas");
  var gl = canvas.getContext("webgl");
  if (!gl) {
    return;
  }

  // setup GLSL programs and lookup locations
  const envmapProgramInfo = webglUtils.createProgramInfo(
      gl, ["envmap-vertex-shader", "envmap-fragment-shader"]);
  const skyboxProgramInfo = webglUtils.createProgramInfo(
      gl, ["skybox-vertex-shader", "skybox-fragment-shader"]);

  // create buffers and fill with vertex data
  const cubeBufferInfo = primitives.createCubeBufferInfo(gl, 1);
  const quadBufferInfo = primitives.createXYQuadBufferInfo(gl);

  // Create a texture.
  const texture = gl.createTexture();
  gl.bindTexture(gl.TEXTURE_CUBE_MAP, texture);

  const faceInfos = [
    {
      target: gl.TEXTURE_CUBE_MAP_POSITIVE_X,
      url: 'resources/images/computer-history-museum/pos-x.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_NEGATIVE_X,
      url: 'resources/images/computer-history-museum/neg-x.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_POSITIVE_Y,
      url: 'resources/images/computer-history-museum/pos-y.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_NEGATIVE_Y,
      url: 'resources/images/computer-history-museum/neg-y.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_POSITIVE_Z,
      url: 'resources/images/computer-history-museum/pos-z.jpg',
    },
    {
      target: gl.TEXTURE_CUBE_MAP_NEGATIVE_Z,
      url: 'resources/images/computer-history-museum/neg-z.jpg',
    },
  ];
  faceInfos.forEach((faceInfo) => {
    const {target, url} = faceInfo;

    // Upload the canvas to the cubemap face.
    const level = 0;
    const internalFormat = gl.RGBA;
    const width = 512;
    const height = 512;
    const format = gl.RGBA;
    const type = gl.UNSIGNED_BYTE;

    // setup each face so it's immediately renderable
    gl.texImage2D(target, level, internalFormat, width, height, 0, format, type, null);

    // Asynchronously load an image
    const image = new Image();
    image.src = url;
    image.addEventListener('load', function() {
      // Now that the image has loaded make copy it to the texture.
      gl.bindTexture(gl.TEXTURE_CUBE_MAP, texture);
      gl.texImage2D(target, level, internalFormat, format, type, image);
      gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
    });
  });
  gl.generateMipmap(gl.TEXTURE_CUBE_MAP);
  gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_LINEAR);

  function radToDeg(r) {
    return r * 180 / Math.PI;
  }

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

  var fieldOfViewRadians = degToRad(60);
  var cameraYRotationRadians = degToRad(0);

  var spinCamera = true;
  // Get the starting time.
  var then = 0;

  requestAnimationFrame(drawScene);

  // Draw the scene.
  function drawScene(time) {
    // convert to seconds
    time *= 0.001;
    // Subtract the previous time from the current time
    var deltaTime = time - then;
    // Remember the current time for the next frame.
    then = time;

    webglUtils.resizeCanvasToDisplaySize(gl.canvas);

    // Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.enable(gl.CULL_FACE);
    gl.enable(gl.DEPTH_TEST);

    // Clear the canvas AND the depth buffer.
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // Compute the projection matrix
    var aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
    var projectionMatrix =
        m4.perspective(fieldOfViewRadians, aspect, 1, 2000);

    // camera going in circle 2 units from origin looking at origin
    var cameraPosition = [Math.cos(time * .1) * 2, 0, Math.sin(time * .1) * 2];
    var target = [0, 0, 0];
    var up = [0, 1, 0];
    // Compute the camera's matrix using look at.
    var cameraMatrix = m4.lookAt(cameraPosition, target, up);

    // Make a view matrix from the camera matrix.
    var viewMatrix = m4.inverse(cameraMatrix);

    // Rotate the cube around the x axis
    var worldMatrix = m4.xRotation(time * 0.11);

    // We only care about direciton so remove the translation
    var viewDirectionMatrix = m4.copy(viewMatrix);
    viewDirectionMatrix[12] = 0;
    viewDirectionMatrix[13] = 0;
    viewDirectionMatrix[14] = 0;

    var viewDirectionProjectionMatrix = m4.multiply(
        projectionMatrix, viewDirectionMatrix);
    var viewDirectionProjectionInverseMatrix =
        m4.inverse(viewDirectionProjectionMatrix);

    // draw the cube
    gl.depthFunc(gl.LESS);  // use the default depth test
    gl.useProgram(envmapProgramInfo.program);
    webglUtils.setBuffersAndAttributes(gl, envmapProgramInfo, cubeBufferInfo);
    webglUtils.setUniforms(envmapProgramInfo, {
      u_world: worldMatrix,
      u_view: viewMatrix,
      u_projection: projectionMatrix,
      u_texture: texture,
      u_worldCameraPosition: cameraPosition,
    });
    webglUtils.drawBufferInfo(gl, cubeBufferInfo);

    // draw the skybox

    // let our quad pass the depth test at 1.0
    gl.depthFunc(gl.LEQUAL);

    gl.useProgram(skyboxProgramInfo.program);
    webglUtils.setBuffersAndAttributes(gl, skyboxProgramInfo, quadBufferInfo);
    webglUtils.setUniforms(skyboxProgramInfo, {
      u_viewDirectionProjectionInverse: viewDirectionProjectionInverseMatrix,
      u_skybox: texture,
    });
    webglUtils.drawBufferInfo(gl, quadBufferInfo);

    requestAnimationFrame(drawScene);
  }
}

main();
</script>
</html>