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webgl-3d-fog-depth-based-issue.html
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - Fog - Depth Based Issue</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<canvas id="canvas"></canvas>
<div id="uiContainer">
<div id="ui"></div>
</div>
</body>
<!-- vertex shader -->
<script id="vertex-shader-3d" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec2 a_texcoord;
uniform mat4 u_worldView;
uniform mat4 u_projection;
varying vec2 v_texcoord;
varying float v_fogDepth;
void main() {
// Multiply the position by the matrix.
gl_Position = u_projection * u_worldView * a_position;
// Pass the texcoord to the fragment shader.
v_texcoord = a_texcoord;
// Pass just the negated z position relative to the camera.
// the camera is looking in the -z direction so normally stuff
// in front of the camera has a negative Z position
// but by negating he we get a positive depth.
v_fogDepth = -(u_worldView * a_position).z;
}
</script>
<!-- fragment shader -->
<script id="fragment-shader-3d" type="x-shader/x-fragment">
precision mediump float;
// Passed in from the vertex shader.
varying vec2 v_texcoord;
varying float v_fogDepth;
// The texture.
uniform sampler2D u_texture;
uniform vec4 u_fogColor;
uniform float u_fogNear;
uniform float u_fogFar;
void main() {
vec4 color = texture2D(u_texture, v_texcoord);
float fogAmount = smoothstep(u_fogNear, u_fogFar, v_fogDepth);
gl_FragColor = mix(color, u_fogColor, fogAmount);
}
</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.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="resources/webgl-utils.js"></script>
<script src="resources/m4.js"></script>
<script src="resources/webgl-lessons-ui.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 program
var program = webglUtils.createProgramFromScripts(gl, ["vertex-shader-3d", "fragment-shader-3d"]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texcoordLocation = gl.getAttribLocation(program, "a_texcoord");
// lookup uniforms
var projectionLocation = gl.getUniformLocation(program, "u_projection");
var worldViewLocation = gl.getUniformLocation(program, "u_worldView");
var textureLocation = gl.getUniformLocation(program, "u_texture");
var fogColorLocation = gl.getUniformLocation(program, "u_fogColor");
var fogNearLocation = gl.getUniformLocation(program, "u_fogNear");
var fogFarLocation = gl.getUniformLocation(program, "u_fogFar");
// Create a buffer for positions
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Put the positions in the buffer
setGeometry(gl);
// provide texture coordinates for the rectangle.
var texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
// Set Texcoords.
setTexcoords(gl);
// Create a texture.
var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
// Fill the texture with a 1x1 blue pixel.
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE,
new Uint8Array([0, 0, 255, 255]));
// Asynchronously load an image
var image = new Image();
image.src = "resources/f-texture.png";
image.addEventListener('load', function() {
// Now that the image has loaded make copy it to the texture.
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA,gl.UNSIGNED_BYTE, image);
// Check if the image is a power of 2 in both dimensions.
if (isPowerOf2(image.width) && isPowerOf2(image.height)) {
// Yes, it's a power of 2. Generate mips.
gl.generateMipmap(gl.TEXTURE_2D);
} else {
// No, it's not a power of 2. Turn of mips and set wrapping to clamp to edge
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
}
});
function isPowerOf2(value) {
return (value & (value - 1)) === 0;
}
function radToDeg(r) {
return r * 180 / Math.PI;
}
function degToRad(d) {
return d * Math.PI / 180;
}
var modelXRotationRadians = degToRad(0);
var modelYRotationRadians = degToRad(0);
var fogColor = [0.8, 0.9, 1, 1];
var settings = {
fov: 60,
fogNear: 3.2,
fogFar: 4.7,
};
webglLessonsUI.setupUI(document.querySelector("#ui"), settings, [
{ type: "slider", key: "fov", min: 1, max: 120, },
{ type: "slider", key: "fogNear", min: 0, max: 7, precision: 3, step: 0.001, },
{ type: "slider", key: "fogFar", min: 0, max: 7, precision: 3, step: 0.001, },
]);
// 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.clearColor(...fogColor);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 3; // 3 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation, size, type, normalize, stride, offset);
// Turn on the texcoord attribute
gl.enableVertexAttribArray(texcoordLocation);
// bind the texcoord buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
// Tell the texcoord attribute how to get data out of texcoordBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
texcoordLocation, size, type, normalize, stride, offset);
// Compute the projection matrix
var fieldOfViewRadians = degToRad(settings.fov);
var aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
var projectionMatrix =
m4.perspective(fieldOfViewRadians, aspect, 1, 2000);
// Compute the camera's matrix
var cameraMatrix = m4.yRotation(time);
// Make a view matrix from the camera matrix.
var viewMatrix = m4.inverse(cameraMatrix);
const numCubes = 8;
for (let i = 0; i < numCubes; ++i) {
var worldViewMatrix = m4.yRotate(viewMatrix, i / numCubes * Math.PI * 2);
worldViewMatrix = m4.translate(worldViewMatrix, 0, 0, -5);
// Set the matrices.
gl.uniformMatrix4fv(projectionLocation, false, projectionMatrix);
gl.uniformMatrix4fv(worldViewLocation, false, worldViewMatrix);
// Tell the shader to use texture unit 0 for u_texture
gl.uniform1i(textureLocation, 0);
// set the fog color and near, far settings
gl.uniform4fv(fogColorLocation, fogColor);
gl.uniform1f(fogNearLocation, settings.fogNear);
gl.uniform1f(fogFarLocation, settings.fogFar);
// Draw the geometry.
gl.drawArrays(gl.TRIANGLES, 0, 6 * 6);
}
requestAnimationFrame(drawScene);
}
}
// Fill the buffer with the values that define a cube.
function setGeometry(gl) {
var positions = new Float32Array([
-0.5, -0.5, -0.5,
-0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
-0.5, 0.5, -0.5,
0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
-0.5, -0.5, 0.5,
0.5, -0.5, 0.5,
-0.5, 0.5, 0.5,
-0.5, 0.5, 0.5,
0.5, -0.5, 0.5,
0.5, 0.5, 0.5,
-0.5, 0.5, -0.5,
-0.5, 0.5, 0.5,
0.5, 0.5, -0.5,
-0.5, 0.5, 0.5,
0.5, 0.5, 0.5,
0.5, 0.5, -0.5,
-0.5, -0.5, -0.5,
0.5, -0.5, -0.5,
-0.5, -0.5, 0.5,
-0.5, -0.5, 0.5,
0.5, -0.5, -0.5,
0.5, -0.5, 0.5,
-0.5, -0.5, -0.5,
-0.5, -0.5, 0.5,
-0.5, 0.5, -0.5,
-0.5, -0.5, 0.5,
-0.5, 0.5, 0.5,
-0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
0.5, 0.5, -0.5,
0.5, -0.5, 0.5,
0.5, -0.5, 0.5,
0.5, 0.5, -0.5,
0.5, 0.5, 0.5,
]);
gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW);
}
// Fill the buffer with texture coordinates the cube.
function setTexcoords(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
0, 0,
0, 1,
1, 0,
0, 1,
1, 1,
1, 0,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
0, 1,
1, 0,
0, 1,
1, 1,
1, 0,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
0, 0,
0, 1,
1, 0,
0, 1,
1, 1,
1, 0,
0, 0,
1, 0,
0, 1,
0, 1,
1, 0,
1, 1,
]),
gl.STATIC_DRAW);
}
main();
</script>
</html>