parsegraph-pagingbuffer

pagingbuffer

This module provides a class to manage a sequence of buffer pages for a WebGL buffer.

import PagingBuffer from "parsegraph-pagingbuffer";
import vertShaderSource from "./vert.glsl";
import fragShaderSource from "./frag.glsl";
import Color from "parsegraph-color";

document.addEventListener("DOMContentLoaded", () => {
  const root = document.getElementById("demo");
  root.style.position = "relative";
  root.style.overflow = "hidden";
  const trailerCanvas = document.createElement("canvas");
  trailerCanvas.style.position = "absolute";
  trailerCanvas.style.left = "0px";
  trailerCanvas.style.right = "0px";
  trailerCanvas.style.top = "0px";
  trailerCanvas.style.bottom = "0px";
  trailerCanvas.style.zIndex = "0";
  root.appendChild(trailerCanvas);
  const gl = trailerCanvas.getContext("webgl");
  const prog = gl.createProgram();
  const vShader = gl.createShader(gl.VERTEX_SHADER);
  const fShader = gl.createShader(gl.FRAGMENT_SHADER);
  gl.shaderSource(vShader, vertShaderSource);
  gl.compileShader(vShader);
  gl.attachShader(prog, vShader);

  gl.shaderSource(fShader, fragShaderSource);
  gl.compileShader(fShader);
  gl.attachShader(prog, fShader);

  gl.linkProgram(prog);
  const pg = new PagingBuffer(gl, prog);
  pg.defineAttrib("a_texCoord", 2);
  pg.defineAttrib("a_color", 3);
  pg.defineAttrib("start", 2);
  pg.defineAttrib("end", 2);
  pg.defineAttrib("duration", 1);
  pg.defineAttrib("size", 1);
  pg.defineAttrib("startTime", 1);

  const interval = 6000;

  pg.clear();
  pg.addPage();
  const playing = new Date();
  if (trailerCanvas.width !== root.clientWidth) {
    trailerCanvas.width = root.clientWidth;
  }
  if (trailerCanvas.height !== root.clientHeight) {
    trailerCanvas.height = root.clientHeight;
  }

  const addTrailer = (startX: number, startY: number, color: Color) => {
    const size = Math.floor(2 + 100 * Math.random());
    const sw = root.clientWidth;
    const sh = root.clientHeight;
    const end = [Math.random() * sw, Math.random() * sh];
    const startTime = Date.now() - playing.getTime();
    const duration = Math.random() * (interval - 1000);
    [
      [
        [1, 1],
        [-1, 1],
        [-1, -1],
      ],
      [
        [1, 1],
        [-1, -1],
        [1, -1],
      ],
    ].forEach((texCoords) => {
      texCoords.forEach((texCoord) => {
        pg.append2D("start", startX / sw, (sh - startY) / sh);
        pg.append2D("end", end[0] / sw, (sh - end[1]) / sh);
        pg.append2D("a_texCoord", texCoord[0], texCoord[1]);
        pg.append3D("a_color", color.r(), color.g(), color.b());
        pg.append1D("startTime", startTime);
        pg.append1D("duration", duration);
        pg.append1D("size", size / Math.min(sw, sh));
      });
    });
  };

  for (let i = 0; i < 100; ++i) {
    const x = Math.random() * root.clientWidth;
    const y = Math.random() * root.clientHeight;
    addTrailer(x, y, Color.random());
  }

  const animate = () => {
    const sw = trailerCanvas.width;
    const sh = trailerCanvas.height;
    gl.viewport(0, 0, sw, sh);
    const pct = Math.min(interval, Date.now() - playing.getTime()) / interval;
    gl.clearColor(0, 0, 0, 0);
    gl.clear(gl.COLOR_BUFFER_BIT);

    gl.useProgram(prog);
    gl.uniform1f(
      gl.getUniformLocation(prog, "time"),
      Date.now() - playing.getTime()
    );
    gl.uniform1f(gl.getUniformLocation(prog, "aspectRatio"), sw / sh);
    pg.renderPages();
    gl.useProgram(null);
    if (pct < 1) {
      requestAnimationFrame(animate);
    }
  };
  requestAnimationFrame(animate);
});