Positionable Camera

To get an arbitrary viewpoint！

This part is corresponding to Ray Tracing In One Weekend: Positionable Camera.

Render image

function RenderImage(canvas: HTMLCanvasElement, generateColor: (ray: Ray, world: World, depth: number) => Vector3) {

positionable-camera render image setup

    const width = canvas.width;
    const height = canvas.height
    const context = canvas.getContext('2d');
    const imageData = context.getImageData(0, 0, width, height);

    const world = new World()
        .addObject(new Sphere(new Vector3(0, 0, 1), 0.5, new Lambertian(new Vector3(0.1, 0.2, 0.5))))
        .addObject(new Sphere(new Vector3(0, 100.5, 1), 100, new Lambertian(new Vector3(0.8, 0.8, 0))))
        .addObject(new Sphere(new Vector3(1, 0, 1), 0.5, new Metal(new Vector3(0.8, 0.6, 0.2))))
        .addObject(new Sphere(new Vector3(-1, 0, 1), 0.5, new Dielectric(1.5)));

pay attention to the coordinate conversion: $y$ -> $-y$ and $z$ -> $-z$ .

    const lookFrom = new Vector3(-2, -2, -1);
    const lookAt = new Vector3(0, 0, 1);
    const up = new Vector3(0, -1, 0);

fov: field of view

    const fov = Math.PI / 2;
    const aspect = width / height;

use PositionableCamera:

    const camera = new PositionableCamera(fov, aspect, lookFrom, lookAt, up);

positionable-camera paint

    const samples = 50;
    const maxDepth = 50;

    for (let x = 0; x < width; ++x) {
        for (let y = 0; y < height; ++y) {
            const color = new Vector3(0, 0, 0);
            for (let k = 0; k < samples; ++k) {
                const u = (x + Math.random()) / width;
                const v = (y + Math.random()) / height;
                const ray = camera.getRay(u, v);

                color.add(generateColor(ray, world, maxDepth));
            }
            color.divideScalar(samples);

            //
            const r = Math.sqrt(color.x);
            const g = Math.sqrt(color.y);
            const b = Math.sqrt(color.z);

            //
            const n = (y * width + x) * 4;
            imageData.data[n] = r * 255;
            imageData.data[n + 1] = g * 255;
            imageData.data[n + 2] = b * 255;
            imageData.data[n + 3] = 255;
        }
    }
    context.putImageData(imageData, 0, 0);
}

Result

Zoom in:

positionable-camera trivial setup

positionable-camera imports

import { onMount } from 'svelte';
import { Vector3, Ray } from 'three';
import { World } from '../../common/with-material/world.js';
import { Sphere } from '../../common/with-material/sphere.js';
import { PositionableCamera } from '../../common/positionable-camera.js';
import { Lambertian, Dielectric, Metal } from '../../common/with-material/material.js';

function GenerateColor(ray: Ray, world: World, depth: number, generateColor: (ray: Ray, world: World, depth: number) => Vector3) {
    if (depth <= 0) {
        return new Vector3(0, 0, 0);
    }

    const record = world.hit(ray, { min: 0.001, max: Number.MAX_SAFE_INTEGER });
    if (record) {
        const { scattered, attenuation } = record.material.scatter(ray, record);
        if (scattered) {
            const color = generateColor(
                scattered,
                world,
                depth - 1
            );
            return color.multiply(attenuation);
        }
        return new Vector3(0, 0, 0);
    }

    const unitDirection = ray.direction.clone().normalize();
    const t = 0.5 * (unitDirection.y + 1);
    const blend = new Vector3(0.5, 0.7, 1.0).lerp(new Vector3(1, 1, 1), t);
    return blend;

}

export default function Section() {
    let canvas: HTMLCanvasElement;

    onMount(() => {
        function generateColor(ray: Ray, world: World, depth: number) {
            //@ts-ignore
            <GenerateColor />;
        };

        //@ts-ignore
        <RenderImage />;
    });

    let width = 600;
    let height = 300;

    <div class="container">
        <canvas bindRef={canvas} width={width} height={height}></canvas>
    </div>
}

Table of Contents

Positionable Camera

Render image

Result

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