blaze-2d/lib/src/shapes/triangle.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 triangle
const baseVertices = {
    tc: vec2.fromValues(0.5, 1),
    bl: vec2.fromValues(0, 0),
    br: vec2.fromValues(1, 0),
};
const indices = new Uint16Array([0, 1, 2]);
const uvs = new Float32Array([0, 0, 1, 0, 0.5, 1]);
/**
 * Represents a triangle in 2D space with a width and height.
 */
export default class Triangle extends Shape {
    /**
     * Creates a new {@link Triangle} instance with dimensions, position and rotation.
     *
     * @param width The width of the triangle (x size)
     * @param height The height of the triangle (y size)
     * @param position The triangle's position in world space, default is [0, 0]
     * @param rotation The triangle's rotation, default is 0.
     */
    constructor(width, height, position, rotation) {
        super();
        if (position)
            this.setPosition(position);
        if (rotation)
            this.setRotation(rotation);
        this.setWidth(width);
        this.setHeight(height);
    }
    /**
     * Calculates the triangle'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 triangle'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;
        // vector to get from tc vertex to bc
        // worldLocalRotated[2] is tc
        const tcbc = vec2.sub(vec2.create(), vec2.fromValues(worldLocalRotated[2][0], worldLocalRotated[0][1]), worldLocalRotated[2]);
        // centre of the triangle after translations
        // TODO: Could change centre calculation to Midpoint formula
        const centre = vec2.scaleAndAdd(vec2.create(), worldLocalRotated[2], tcbc, 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 triangle.
     *
     * These are the vertices for a triangle scaled to the width and height of the {@link Triangle} instance.
     *
     * @returns The triangles base vertices
     */
    getBaseVertices() {
        const base = [
            baseVertices.bl,
            vec2.multiply(vec2.create(), baseVertices.br, vec2.fromValues(this.width, 1)),
            vec2.multiply(vec2.create(), baseVertices.tc, vec2.fromValues(this.width, this.height)),
        ];
        const temp = vec2.create();
        const offset = vec2.fromValues(this.width / 2, this.height / 2);
        const centred = base.map((v) => {
            vec2.sub(temp, v, offset);
            return vec2.clone(temp);
        });
        return centred;
    }
    /**
     * Gets the triangle's vertex indices for drawing using element arrays.
     *
     * @param offset An offset to apply to each index
     * @returns The triangle's vertex indices with the given offset added to each index
     */
    getIndices(offset = 0) {
        return indices.map((i) => i + offset);
    }
    /**
     * Calculates the triangles's UV coords to be used for texture rendering.
     *
     * @returns the triangle's UV coords
     */
    getUVCoords() {
        return uvs;
    }
    /**
     * Sets the triangle's width.
     *
     * @throws When the the provided width is < 0
     *
     * @param width The triangle's new width
     */
    setWidth(width) {
        if (width < 0)
            return void Logger.error("Triangle", "Width cannot be < 0.");
        this.width = width;
    }
    /**
     * Gets the triangle's width in world space units.
     *
     * @returns The triangle's width in world space
     */
    getWidth() {
        return this.width;
    }
    /**
     * Sets the triangle's height.
     *
     * @throws When the the provided height is < 0
     *
     * @param height The triangle's new height
     */
    setHeight(height) {
        if (height < 0)
            return void Logger.error("Triangle", "Height cannot be < 0.");
        this.height = height;
    }
    /**
     * Gets the triangle's height in world space units.
     *
     * @returns The triangle's height in world space
     */
    getHeight() {
        return this.height;
    }
}
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