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transform_feedback_instanced.html
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transform_feedback_instanced.html
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<!DOCTYPE html>
<html lang="en">
<head>
<title>WebGL 2 Samples - transform_feedback_instanced</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
<link rel="stylesheet" href="style.css">
<script src="utility.js"></script>
<script src="third-party/gl-matrix-min.js"></script>
<script src="third-party/noise3D.js"></script>
</head>
<body>
<div id="info">WebGL 2 Samples - transform_feedback_instanced</div>
<p id="description">Demonstrates how to combine transform feedback and instanced drawing. Agents are wandering randomly.</p>
<!-- WebGL 2 shaders -->
<script id="vs-emit" type="x-shader/x-vertex">
#version 300 es
#define OFFSET_LOCATION 0
#define ROTATION_LOCATION 1
#define M_2PI 6.28318530718
// We simulate the wandering of agents using transform feedback in this vertex shader
// The simulation goes like this:
// Assume there's a circle in front of the agent whose radius is WANDER_CIRCLE_R
// the origin of which has a offset to the agent's pivot point, which is WANDER_CIRCLE_OFFSET
// Each frame we pick a random point on this circle
// And the agent moves MOVE_DELTA toward this target point
// We also record the rotation facing this target point, so it will be the base rotation
// for our next frame, which means the WANDER_CIRCLE_OFFSET vector will be on this direction
// Thus we fake a smooth wandering behavior
#define MAP_HALF_LENGTH 1.01
#define WANDER_CIRCLE_R 0.01
#define WANDER_CIRCLE_OFFSET 0.04
#define MOVE_DELTA 0.001
precision highp float;
precision highp int;
uniform float u_time;
layout(location = OFFSET_LOCATION) in vec2 a_offset;
layout(location = ROTATION_LOCATION) in float a_rotation;
out vec2 v_offset;
out float v_rotation;
float rand(vec2 co)
{
return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}
void main()
{
float theta = M_2PI * rand(vec2(u_time, a_rotation + a_offset.x + a_offset.y));
float cos_r = cos(a_rotation);
float sin_r = sin(a_rotation);
mat2 rot = mat2(
cos_r, sin_r,
-sin_r, cos_r
);
vec2 p = WANDER_CIRCLE_R * vec2(cos(theta), sin(theta)) + vec2(WANDER_CIRCLE_OFFSET, 0.0);
vec2 move = normalize(rot * p);
v_rotation = atan(move.y, move.x);
v_offset = a_offset + MOVE_DELTA * move;
// wrapping at edges
v_offset = vec2 (
v_offset.x > MAP_HALF_LENGTH ? - MAP_HALF_LENGTH : ( v_offset.x < - MAP_HALF_LENGTH ? MAP_HALF_LENGTH : v_offset.x ) ,
v_offset.y > MAP_HALF_LENGTH ? - MAP_HALF_LENGTH : ( v_offset.y < - MAP_HALF_LENGTH ? MAP_HALF_LENGTH : v_offset.y )
);
gl_Position = vec4(v_offset, 0.0, 1.0);
}
</script>
<!-- Unsused -->
<script id="fs-emit" type="x-shader/x-fragment">
#version 300 es
precision highp float;
precision highp int;
void main()
{
}
</script>
<script id="vs-draw" type="x-shader/x-vertex">
#version 300 es
#define OFFSET_LOCATION 0
#define ROTATION_LOCATION 1
#define POSITION_LOCATION 2
#define COLOR_LOCATION 3
precision highp float;
precision highp int;
layout(location = POSITION_LOCATION) in vec2 a_position;
layout(location = ROTATION_LOCATION) in float a_rotation;
layout(location = OFFSET_LOCATION) in vec2 a_offset;
layout(location = COLOR_LOCATION) in vec3 a_color;
out vec3 v_color;
void main()
{
v_color = a_color;
float cos_r = cos(a_rotation);
float sin_r = sin(a_rotation);
mat2 rot = mat2(
cos_r, sin_r,
-sin_r, cos_r
);
gl_Position = vec4(rot * a_position + a_offset, 0.0, 1.0);
}
</script>
<script id="fs-draw" type="x-shader/x-fragment">
#version 300 es
#define ALPHA 0.9
precision highp float;
precision highp int;
in vec3 v_color;
out vec4 color;
void main()
{
color = vec4(v_color * ALPHA, ALPHA);
}
</script>
<script>
(function () {
'use strict';
// -- Init Canvas
var canvas = document.createElement('canvas');
canvas.width = Math.min(window.innerWidth, window.innerHeight);
canvas.height = canvas.width;
document.body.appendChild(canvas);
// -- Init WebGL Context
var gl = canvas.getContext('webgl2', { antialias: false });
var isWebGL2 = !!gl;
if(!isWebGL2)
{
document.getElementById('info').innerHTML = 'WebGL 2 is not available. See <a href="https://www.khronos.org/webgl/wiki/Getting_a_WebGL_Implementation">How to get a WebGL 2 implementation</a>';
return;
}
canvas.addEventListener("webglcontextlost", function(event) {
event.preventDefault();
}, false);
// -- Init Program
var PROGRAM_TRANSFORM = 0;
var PROGRAM_DRAW = 1;
var programs = initPrograms();
// -- Initialize data
var NUM_INSTANCES = 1000;
var currentSourceIdx = 0;
var trianglePositions = new Float32Array([
0.015, 0.0,
-0.010, 0.010,
-0.010, -0.010,
]);
var instanceOffsets = new Float32Array(NUM_INSTANCES * 2);
var instanceRotations = new Float32Array(NUM_INSTANCES * 1);
var instanceColors = new Float32Array(NUM_INSTANCES * 3);
for (var i = 0; i < NUM_INSTANCES; ++i) {
var oi = i * 2;
var ri = i;
var ci = i * 3;
instanceOffsets[oi] = Math.random() * 2.0 - 1.0;
instanceOffsets[oi + 1] = Math.random() * 2.0 - 1.0;
instanceRotations[i] = Math.random() * 2 * Math.PI;
instanceColors[ci] = Math.random();
instanceColors[ci + 1] = Math.random();
instanceColors[ci + 2] = Math.random();
}
// -- Init Vertex Array
var OFFSET_LOCATION = 0;
var ROTATION_LOCATION = 1;
var POSITION_LOCATION = 2; // this is vertex position of the instanced geometry
var COLOR_LOCATION = 3;
var NUM_LOCATIONS = 4;
var drawTimeLocation = gl.getUniformLocation(programs[PROGRAM_DRAW], 'u_time');
var vertexArrays = [gl.createVertexArray(), gl.createVertexArray()];
// Transform feedback objects track output buffer state
var transformFeedbacks = [gl.createTransformFeedback(), gl.createTransformFeedback()];
var vertexBuffers = new Array(vertexArrays.length);
for (var va = 0; va < vertexArrays.length; ++va) {
gl.bindVertexArray(vertexArrays[va]);
vertexBuffers[va] = new Array(NUM_LOCATIONS);
vertexBuffers[va][OFFSET_LOCATION] = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffers[va][OFFSET_LOCATION]);
gl.bufferData(gl.ARRAY_BUFFER, instanceOffsets, gl.STREAM_COPY);
gl.vertexAttribPointer(OFFSET_LOCATION, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(OFFSET_LOCATION);
vertexBuffers[va][ROTATION_LOCATION] = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffers[va][ROTATION_LOCATION]);
gl.bufferData(gl.ARRAY_BUFFER, instanceRotations, gl.STREAM_COPY);
gl.vertexAttribPointer(ROTATION_LOCATION, 1, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(ROTATION_LOCATION);
vertexBuffers[va][POSITION_LOCATION] = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffers[va][POSITION_LOCATION]);
gl.bufferData(gl.ARRAY_BUFFER, trianglePositions, gl.STATIC_DRAW);
gl.vertexAttribPointer(POSITION_LOCATION, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(POSITION_LOCATION);
vertexBuffers[va][COLOR_LOCATION] = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffers[va][COLOR_LOCATION]);
gl.bufferData(gl.ARRAY_BUFFER, instanceColors, gl.STATIC_DRAW);
gl.vertexAttribPointer(COLOR_LOCATION, 3, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(COLOR_LOCATION);
gl.vertexAttribDivisor(COLOR_LOCATION, 1); // attribute used once per instance
gl.bindVertexArray(null);
gl.bindBuffer(gl.ARRAY_BUFFER, null);
// Set up output
gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, transformFeedbacks[va]);
gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 0, vertexBuffers[va][OFFSET_LOCATION]);
gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 1, vertexBuffers[va][ROTATION_LOCATION]);
gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, null);
}
render();
function initPrograms() {
// Setup program for transform feedback shaders
function createShader(gl, source, type) {
var shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
return shader;
}
var vshaderTransform = createShader(gl, getShaderSource('vs-emit'), gl.VERTEX_SHADER);
var fshaderTransform = createShader(gl, getShaderSource('fs-emit'), gl.FRAGMENT_SHADER);
var programTransform = gl.createProgram();
gl.attachShader(programTransform, vshaderTransform);
gl.deleteShader(vshaderTransform);
gl.attachShader(programTransform, fshaderTransform);
gl.deleteShader(fshaderTransform);
var varyings = ['v_offset', 'v_rotation'];
gl.transformFeedbackVaryings(programTransform, varyings, gl.SEPARATE_ATTRIBS);
gl.linkProgram(programTransform);
// check
var log = gl.getProgramInfoLog(programTransform);
if (log) {
console.log(log);
}
log = gl.getShaderInfoLog(vshaderTransform);
if (log) {
console.log(log);
}
// Setup program for draw shader
var programDraw = createProgram(gl, getShaderSource('vs-draw'), getShaderSource('fs-draw'));
var programs = [programTransform, programDraw];
return programs;
}
function transform() {
var programTransform = programs[PROGRAM_TRANSFORM];
var destinationIdx = (currentSourceIdx + 1) % 2;
// Toggle source and destination VBO
var sourceVAO = vertexArrays[currentSourceIdx];
var destinationTransformFeedback = transformFeedbacks[destinationIdx];
gl.useProgram(programTransform);
gl.bindVertexArray(sourceVAO);
gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, destinationTransformFeedback);
// NOTE: The following two lines shouldn't be necessary, but are required to work in ANGLE
// due to a bug in its handling of transform feedback objects.
// https://bugs.chromium.org/p/angleproject/issues/detail?id=2051
gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 0, vertexBuffers[destinationIdx][OFFSET_LOCATION]);
gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 1, vertexBuffers[destinationIdx][ROTATION_LOCATION]);
// Attributes per-vertex when doing transform feedback needs setting to 0 when doing transform feedback
gl.vertexAttribDivisor(OFFSET_LOCATION, 0);
gl.vertexAttribDivisor(ROTATION_LOCATION, 0);
// Turn off rasterization - we are not drawing
gl.enable(gl.RASTERIZER_DISCARD);
// Update position and rotation using transform feedback
gl.beginTransformFeedback(gl.POINTS);
gl.drawArrays(gl.POINTS, 0, NUM_INSTANCES);
gl.endTransformFeedback();
// Restore state
gl.disable(gl.RASTERIZER_DISCARD);
gl.useProgram(null);
gl.bindBuffer(gl.ARRAY_BUFFER, null);
gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, null);
gl.bindBuffer(gl.TRANSFORM_FEEDBACK_BUFFER, null);
// Ping pong the buffers
currentSourceIdx = (currentSourceIdx + 1) % 2;
}
function render() {
// Rotate triangles
transform();
// Set the viewport
gl.viewport(0, 0, canvas.width, canvas.height - 10);
// Clear color buffer
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.bindVertexArray(vertexArrays[currentSourceIdx]);
// Attributes per-instance when drawing sets back to 1 when drawing instances
gl.vertexAttribDivisor(OFFSET_LOCATION, 1);
gl.vertexAttribDivisor(ROTATION_LOCATION, 1);
gl.useProgram(programs[PROGRAM_DRAW]);
// Enable blending
gl.enable(gl.BLEND);
gl.blendFunc(gl.SRC_ALPHA, gl.ONE);
// Set uniforms
var time = Date.now();
gl.uniform1f(drawTimeLocation, time);
gl.drawArraysInstanced(gl.TRIANGLES, 0, 3, NUM_INSTANCES);
requestAnimationFrame(render);
}
// If you have a long-running page, and need to delete WebGL resources, use:
//
// gl.deleteProgram(programs[PROGRAM_TRANSFORM]);
// gl.deleteProgram(programs[PROGRAM_DRAW]);
// for (var i = 0; i < 2; ++i) {
// for (var j = 0; j < Particle.MAX; ++j) {
// gl.deleteBuffer(vertexBuffers[i][j]);
// }
// }
// gl.deleteVertexArray(vertexArrays[PROGRAM_TRANSFORM]);
// gl.deleteVertexArray(vertexArrays[PROGRAM_DRAW]);
// gl.deleteTransformFeedback(transformFeedbacks[0]);
// gl.deleteTransformFeedback(transformFeedbacks[1]);
})();
</script>
<div id="highlightedLines" style="display: none">#L221-L367</div>
</body>
</html>