blaze-2d/lib/src/shapes/circle.js

A fast and simple WebGL 2 2D game engine written in TypeScript

import { vec2 } from "gl-matrix";
import Logger from "../logger";
import { applyRotation, applyTranslation } from "../utils/vectors";
import Shape from "./shape";
// vertices for a
const baseVertices = {
    tl: vec2.fromValues(0, 1),
    tr: vec2.fromValues(1, 1),
    bl: vec2.fromValues(0, 0),
    br: vec2.fromValues(1, 0),
};
const indices = new Uint16Array([0, 1, 2, 0, 2, 3]);
const uvs = new Float32Array([0, 1, 1, 1, 1, 0, 0, 0]);
/**
 * Represents a circle in 2D space with a radius and centre.
 */
export default class Circle extends Shape {
    /**
     * Creates a new {@link Circle} instance with a radius, position and rotation.
     *
     * @param radius The radius of the circle
     * @param centre The circle's centre in world space, default is [0, 0]
     * @param rotation The circle's rotation, default is 0.
     */
    constructor(radius, centre, rotation) {
        super();
        if (centre)
            this.setPosition(centre);
        if (rotation)
            this.setRotation(rotation);
        this.setRadius(radius);
    }
    /**
     * Calculates the circle's vertices relative to the provided origin in world space.
     *
     * @param origin The origin to calculate the vertices relative to, should be a world position
     * @param rotation An optional world space rotation to apply to the vertices
     * @param returnVecs Wether or not to return the vertices as vec2s or raw numbers
     * @returns The circle's vertices relative to the provided origin in world space
     */
    getVerticesWorld(origin, rotation, returnVecs = false) {
        const base = this.getBaseVertices();
        const world = applyTranslation(base, origin);
        const worldLocal = applyTranslation(world, this.getPosition());
        const worldLocalRotated = rotation ? applyRotation(worldLocal, origin, rotation) : worldLocal;
        // const worldLocalTranslation = worldRotated;
        // vector to get from tl vertex to br vertex
        const tlbr = vec2.sub(vec2.create(), worldLocalRotated[1], worldLocalRotated[3]);
        // centre of the rectangle after translations
        const centre = vec2.scaleAndAdd(vec2.create(), worldLocalRotated[3], tlbr, 0.5);
        const worldLocalRotatedLocalRot = applyRotation(worldLocalRotated, centre, this.getRotation());
        // const worldLocalTransRot = worldLocalTranslation;
        if (returnVecs)
            return worldLocalRotatedLocalRot;
        const final = [];
        worldLocalRotatedLocalRot.forEach((v) => final.push(...v));
        return final;
    }
    /**
     * Calculates the base vertices of the circle.
     *
     * These vertices are the base vertices for a quad, scaled to the diameter of the {@link Circle} instance.
     *
     * @returns The circle's base vertices
     */
    getBaseVertices() {
        const diameter = this.radius * 2;
        const base = [
            baseVertices.bl,
            this.vertexScale(baseVertices.br, [diameter, 1]),
            this.vertexScale(baseVertices.tr, [diameter, diameter]),
            this.vertexScale(baseVertices.tl, [1, diameter]),
        ];
        const temp = vec2.create();
        const offset = vec2.fromValues(this.radius, this.radius);
        const centred = base.map((v) => {
            vec2.sub(temp, v, offset);
            return vec2.clone(temp);
        });
        return centred;
    }
    /**
     * Gets the circle's vertex indices for drawing using element arrays.
     *
     * @param offset An offset to apply to each index
     * @returns The circle's vertex indices with the given offset added to each index
     */
    getIndices(offset = 0) {
        return indices.map((i) => i + offset);
    }
    /**
     * Calculates the circle's UV coords to be used for texture rendering.
     *
     * @returns the circle's UV coords
     */
    getUVCoords() {
        return uvs;
    }
    /**
     * Scales the first vector by the components in the second vector, returning the resultant vector.
     *
     * @param v1 The first vector
     * @param v2 The second vector
     * @returns A new vector with the scaled components
     */
    vertexScale(v1, v2) {
        return [v1[0] * v2[0], v1[1] * v2[1]];
    }
    /**
     * Sets the circle's radius.
     *
     * @throws When the provided radius is < 0
     *
     * @param radius The circle's new radius
     */
    setRadius(radius) {
        if (radius < 0)
            return void Logger.error("Circle", "Radius cannot be < 0.");
        this.radius = radius;
    }
    /**
     * Gets the radius of the circle.
     *
     * @returns The radius of the circle
     */
    getRadius() {
        return this.radius;
    }
}
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