Generate vertices for a cylinder
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@ -1,5 +1,90 @@
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"use strict";
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(() => {
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const makeCylinder = (meridians = 3, parallels = 3) => {
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// The number of meridians dividing the sphere's surface.
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// Two meridians would make an XZ plane.
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if (meridians < 3) {
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throw "meridians must be ≥ 3";
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}
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// The number of parallels, including the poles, dividing the sphere's surface.
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// Two parallels would make a vertical line segment.
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if (parallels < 3) {
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throw "parallels must be ≥ 3";
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}
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const radius = 1;
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const positions = new Float32Array(meridians * parallels * 3);
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let positionsIdx = 0;
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for (let p = 0; p < parallels; p++) {
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const y = -radius + p * 2 * radius / parallels;
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for (let m = 0; m < meridians; m++) {
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const θ = 2 * Math.PI / meridians;
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const x = Math.sin(θ) * radius;
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const z = Math.cos(θ) * radius;
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const currPosition = [
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Math.sin(θ) * radius,
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y,
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Math.cos(θ) * radius,
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];
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for (const coord of currPosition) {
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positions[positionsIdx++] = coord;
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}
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}
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}
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const indices = new Uint16Array(meridians * (parallels - 1) * 6);
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const textureCoords = new Float32Array(meridians * (parallels - 1) * 12);
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let indicesIdx = 0;
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let textureCoordsIdx = 0;
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for (let p = 0; p < parallels - 1; p++) {
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for (let m = 0; m < meridians; m++) {
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const lowerLeft = p * meridians + m;
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const lowerRight = p * meridians + (m + 1) % meridians;
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const upperLeft = (p + 1) * meridians + m;
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const upperRight = (p + 1) * meridians + (m + 1) % meridians;
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const currIndices = [
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// Lower triangle
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lowerLeft, lowerRight, upperRight,
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// Upper triangle
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lowerLeft, upperRight, upperLeft,
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];
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for (const index of currIndices) {
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indices[indicesIdx++] = index;
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}
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const currTextureCoords = [
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// Lower triangle
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m / meridians, p / parallels,
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(m + 1) / meridians, p / parallels,
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(m + 1) / meridians, (p + 1) / parallels,
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// Upper triangle
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m / meridians, p / parallels,
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(m + 1) / meridians, (p + 1) / parallels,
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m / meridians, (p + 1) / parallels,
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];
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for (const coord of currTextureCoords) {
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textureCoords[textureCoordsIdx++] = coord;
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}
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}
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}
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for (let p = 0; p < parallels; p++) {
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for (let m = 0; m < meridians; m++) {
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/*
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*/
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}
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}
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return { positions, textureCoords, indices };
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}
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console.log(makeCylinder());
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const initShaderProgram = (gl) => {
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const vShaderSrc = `
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attribute vec3 position;
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