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HTML

              
                <canvas id="canvas" width="800" height="600">
              
            
!

CSS

              
                body {background:black}

canvas {border:1px solid darkgray}
              
            
!

JS

              
                type Vect2d = { x: number; y: number };
type Vect3d = { x: number; y: number; x: number };
type RGBA = { r: number; g: number; b: number; a: number };

const BLACK: RGBA = {r:0,g:0,b:0,a:255}
const RED: RGBA = {r:255,g:0,b:0,a:255}
const GREEN: RGBA = {r:0,g:255,b:0,a:255}
const BLUE: RGBA = {r:0,g:0,b:255,a:255}
const YELLOW: RGBA = {r:255,g:255,b:0,a:255}
const PURPLE: RGBA = {r:255,g:0,b:255,a:255}
const TEAL: RGBA = {r:0,g:255,b:255,a:255}

const FOV = 90

const cvs = document.getElementById("canvas");
const { width, height } = cvs;
const ctx = cvs.getContext("2d");
const z0 = (width/2)/Math.tan((FOV/2)*Math.PI/180)

class URLTexture {
	private imageData
	private width: number
	private height: number
	
	constructor(url) {
		const img = new Image()
		img.onload = () => {
			ctx.drawImage(img, 0, 0);
    	this.imageData = ctx.getImageData(0, 0, img.width, img.height).data;
			alert(this.imageData)
		}
		img.src = url
		this.width = img.width
		this.height = img.height
	}
	
	public getValue({x,y}: Vect2d): RGBA {
		if (x >= this.width) {
			x = this.width - 1
		}
		
		if (y >= this.height) {
			y = this.height - 1
		}
		
		return {
			r: this.imageData[(y * 4 * this.height) + (x * 4)],
			g: this.imageData[(y * 4 * this.height) + (x * 4) + 1],
			b: this.imageData[(y * 4 * this.height) + (x * 4) + 2],
			a: this.imageData[(y * 4 * this.height) + (x * 4) + 3]
		}
	}
}

class Triangle {
	private vertices: Vect3d[3]
  private worldCoords: Vect3d[3]
	private drawPoints: Vect3d[3]
	public averageZ: number
	public normalZ: number
	
	constructor(vertices: Vect3d[3], color: RGBA) {
		this.vertices = vertices
		this.color = color
		this.translate = {x:0,y:0,z:0}
		this.rotation = {x:0,y:0,z:0}
	}
	
	public calculateWorldCoords(position,rotation) {
		this.worldCoords = this.vertices
		
		this.worldCoords = this.worldCoords.map(vertex => rotate(vertex,rotation))
		
		this.worldCoords=this.worldCoords.map(vertex => translate(vertex,position))
		
		this.averageZ = (this.worldCoords[0].z + this.worldCoords[1].z + this.worldCoords[2].z) / 3
	}
	
	public calculateDrawPoints() {
		this.drawPoints=this.worldCoords.map(vertex => applyPerspective(vertex))
		
		this.drawPoints=this.drawPoints.map(vertex => centerScreen(vertex))
		
		this.normalZ = (this.drawPoints[1].x - this.drawPoints[0].x) * (this.drawPoints[2].y - this.drawPoints[0].y) - (this.drawPoints[1].y - this.drawPoints[0].y) * (this.drawPoints[2].x - this.drawPoints[0].x)
	}
	
	public draw(screenBuffer) {
		if (!this.drawPoints.length) return
		let aux
		
		if (this.drawPoints[0].y > this.drawPoints[1].y) {
			aux = this.drawPoints[0]
			this.drawPoints[0] = this.drawPoints[1]
			this.drawPoints[1] = aux
		}
		
		if (this.drawPoints[0].y > this.drawPoints[2].y) {
			aux = this.drawPoints[0]
			this.drawPoints[0] = this.drawPoints[2]
			this.drawPoints[2] = aux
		}
		
		if (this.drawPoints[1].y > this.drawPoints[2].y) {
			aux = this.drawPoints[1]
			this.drawPoints[1] = this.drawPoints[2]
			this.drawPoints[2] = aux
		}
		
		if (this.drawPoints[0].y < this.drawPoints[1].y) {
			const slope1 = (this.drawPoints[1].x - this.drawPoints[0].x) / (this.drawPoints[1].y - this.drawPoints[0].y)
			const slope2 = (this.drawPoints[2].x - this.drawPoints[0].x) / (this.drawPoints[2].y - this.drawPoints[0].y)
			for (let i = 0; i <= this.drawPoints[1].y - this.drawPoints[0].y; i++) {
				let x1 = this.drawPoints[0].x + i * slope1
				let x2 = this.drawPoints[0].x + i * slope2
				let y = this.drawPoints[0].y + i
				
				if (x1 > x2) {
					let aux = x1
					x1 = x2
					x2 = aux
				}
				
				for (let j = x1; j <= x2; j++) {
					screenBuffer.drawPixel({x:j,y},this.color)
				}
			}
		}
		
		if (this.drawPoints[1].y < this.drawPoints[2].y) {
			const slope1 = (this.drawPoints[2].x - this.drawPoints[1].x) / (this.drawPoints[2].y - this.drawPoints[1].y)
			const slope2 = (this.drawPoints[2].x - this.drawPoints[0].x) / (this.drawPoints[2].y - this.drawPoints[0].y)
			const sx = this.drawPoints[2].x - (this.drawPoints[2].y - this.drawPoints[1].y) * slope2
			
			for (let i = 0; i <= this.drawPoints[2].y - this.drawPoints[1].y; i++) {
				let x1 = this.drawPoints[1].x + i * slope1
				let x2 = sx + i * slope2
				let y = this.drawPoints[1].y + i
				
				if (x1 > x2) {
					let aux = x1
					x1 = x2
					x2 = aux
				}
				
				for (let j = x1; j <= x2; j++) {
					screenBuffer.drawPixel({x:j,y},this.color)
				}
			}
		}
	}
}

class Mesh {
	constructor(screenBuffer, vertices, triangles, translate, rotation) {
		this.screenBuffer = screenBuffer;
		this.triangles = triangles;
		this.translate = translate || {x:0,y:0,z:0}
		this.rotation = rotation||{x:0,y:0,z:0}
	}

	public draw() {
		this.triangles.forEach(tri => tri.rotation = this.rotation)
		this.triangles.forEach(tri => tri.translate = this.translate)
		this.triangles.forEach(triangle => triangle.draw(this.screenBuffer))
	}
}

class ScreenBuffer {
	constructor(ctx) {
		this.ctx = ctx;
		this.buffer = ctx.createImageData(width, height);
		this.pixels = this.buffer.data;
		this.numPixels = this.buffer.width * this.buffer.height;
	}

	public drawPixel(coords: Vect2d, color: RGBA) {
		const i = (this.buffer.width * Math.ceil(coords.y) + Math.ceil(coords.x)) * 4;
		this.pixels[i] = color.r;
		this.pixels[i + 1] = color.g;
		this.pixels[i + 2] = color.b;
		this.pixels[i + 3] = color.a;
	}

	public drawBuffer() {
		this.ctx.putImageData(this.buffer, 0, 0);
	}
}

function render(time) {
	// const crateTexture = new URLTexture("https://i.pinimg.com/originals/8e/33/fa/8e33fa90c71e445c9ce287acc0eea64e.jpg")
	// console.log(crateTexture.getValue({x:1,y:1}))
	
	const screenBuffer = new ScreenBuffer(ctx);
	const cubeVerts = [
		{ x: -50, y: -50, z: -50 },
		{ x: -50, y: 50, z: -50 },
		{ x: 50, y: 50, z: -50 },
		{ x: 50, y: -50, z: -50 },
		{ x: -50, y: -50, z: 50 },
		{ x: -50, y: 50, z: 50 },
		{ x: 50, y: 50, z: 50 },
		{ x: 50, y: -50, z: 50 },
	]
	
	const cubeTris = [
		// left
		new Triangle([cubeVerts[0],cubeVerts[1],cubeVerts[3]], YELLOW),
		new Triangle([cubeVerts[1],cubeVerts[2],cubeVerts[3]], YELLOW),
		// right
		new Triangle([cubeVerts[7],cubeVerts[5],cubeVerts[4]], RED),
		new Triangle([cubeVerts[7],cubeVerts[6],cubeVerts[5]], RED),
		// top
		new Triangle([cubeVerts[4],cubeVerts[0],cubeVerts[7]], GREEN),
		new Triangle([cubeVerts[0],cubeVerts[3],cubeVerts[7]], GREEN),
		// bottom
		new Triangle([cubeVerts[1],cubeVerts[6],cubeVerts[2]], PURPLE),
		new Triangle([cubeVerts[1],cubeVerts[5],cubeVerts[6]], PURPLE),
		// back
		new Triangle([cubeVerts[4],cubeVerts[1],cubeVerts[0]], BLUE),
		new Triangle([cubeVerts[4],cubeVerts[5],cubeVerts[1]], BLUE),
		// front
		new Triangle([cubeVerts[3],cubeVerts[2],cubeVerts[7]], TEAL),
		new Triangle([cubeVerts[7],cubeVerts[2],cubeVerts[6]], TEAL),
	]
	
	const cube = new Mesh(screenBuffer, cubeVerts, cubeTris);
	cube.rotation.y += 0.001 * time
	cube.rotation.x += 0.001 * time
	cube.rotation.z += 0.001 * time
	
	let triangles: Triangle[] = []
	
	cube.triangles.forEach(tri => {
		tri.calculateWorldCoords(cube.translate,cube.rotation)
		triangles.push(tri)
	})
	
	triangles.sort((a,b) => a.averageZ > b.averageZ?-1:1)
	triangles.forEach(tri => {
		tri.calculateDrawPoints()
		if (tri.normalZ < 0) {
		tri.draw(screenBuffer)
		}
	})

	screenBuffer.drawBuffer();
	requestAnimationFrame(render);
}
requestAnimationFrame(render);

function translate(original: Vect3d, translation: Vect3d): Vect3d {
	let transformedVector: Vect3d = {x:0,y:0,z:0}
	transformedVector.x = original.x + translation.x
	transformedVector.y = original.y + translation.y
	transformedVector.z = original.z + translation.z
	return transformedVector
} 

function rotate(original: Vect3d, rotation: Vect3d): Vect3d {
	let transformedVector: Vect3d = {x:0,y:0,z:0}
	transformedVector.x = original.x * (Math.cos(rotation.z) * Math.cos(rotation.y)) + 
				 original.y * (Math.cos(rotation.z) * Math.sin(rotation.y) * Math.sin(rotation.x) - Math.sin(rotation.z) * Math.cos(rotation.x)) +
				 original.z * (Math.cos(rotation.z) * Math.sin(rotation.y) * Math.cos(rotation.x) + Math.sin(rotation.z) * Math.sin(rotation.x))
	transformedVector.y = original.x * (Math.sin(rotation.z) * Math.cos(rotation.y)) +
				 original.y * (Math.sin(rotation.z) * Math.sin(rotation.y) * Math.sin(rotation.x) + Math.cos(rotation.z) * Math.cos(rotation.x)) +
				 original.z * (Math.sin(rotation.z) * Math.sin(rotation.y) * Math.cos(rotation.x) - Math.cos(rotation.z) * Math.sin(rotation.x))
	transformedVector.z = original.x * (- Math.sin(rotation.y)) +
				 original.y * (Math.cos(rotation.y) * Math.sin(rotation.x)) +
				 original.z * (Math.cos(rotation.y) * Math.cos(rotation.x))
	return transformedVector
} 

function applyPerspective({x,y,z}: Vect3d): Vect3d {
	let transformedVector: Vect3d = {x:0,y:0,z:0}
	transformedVector.x = x*z0/(z0+z)
	transformedVector.y = y*z0/(z0+z)
	transformedVector.z = z
	return transformedVector
}

function centerScreen(vector: Vect3d) {
	let transformedVector = {x:0,y:0,z:0}
	transformedVector.x = vector.x + width / 2
	transformedVector.y = vector.y + height / 2
	transformedVector.z = vector.z
	return 	transformedVector
}
              
            
!
999px

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