webgl_game/script.ts

import { Vec2 } from "./common.js";
import { Graphics } from "./graphics.js";

const vertexShader = 
    `#version 300 es
     
    in vec2 a_position;
    in vec4 a_color;
    out vec4 color;
    uniform vec2 u_resolution;
     
    void main() {
        vec2 clipSpace = (a_position / u_resolution) * 2.0 - 1.0;

        color = a_color;

        gl_Position = vec4(clipSpace.xy, 0.0, 1.0);
    }
`;

const fragmentShader = 
    `#version 300 es

    precision highp float;
    in vec4 color;
    out vec4 outColor;

    void main() {
      outColor = color;
    }
`;

function initializeContext(canvasId: string): WebGL2RenderingContext | null {
    const canvas  = document.getElementById(canvasId) as HTMLCanvasElement;
    const ctx = canvas.getContext("webgl2", {antialias: false});

    return ctx;

}

function drawTriangle(gfx: Graphics, positions: [Vec2, Vec2, Vec2]) {
    const a_position = gfx.getAttribute("a_position");
    const a_color = gfx.getAttribute("a_color");

    const points: Array<number> = [
        positions[0].x, positions[0].y,
        positions[1].x, positions[1].y,
        positions[2].x, positions[2].y,
    ]

    const color: Array<number> = [
        1, 0, 0, 1,
        0, 1, 0, 1,
        0, 0, 1, 1,
    ];

    a_position.data(gfx.ctx, points, gfx.ctx.STATIC_DRAW);
    a_color.data(gfx.ctx, color, gfx.ctx.STATIC_DRAW);
    gfx.ctx.drawArrays(gfx.ctx.TRIANGLES, 0, 3);
}

function drawTriangleExts(gfx: Graphics, position: Vec2, exts: Vec2) {
    const a_position = gfx.getAttribute("a_position");
    const a_color = gfx.getAttribute("a_color");

    const points: Array<number> = [
        position.x, position.y,
        position.x + exts.x, position.y,
        position.x, position.y + exts.y,
    ]

    const color: Array<number> = [
        1, 0, 0, 1,
        0, 1, 0, 1,
        0, 0, 1, 1,
    ];

    a_position.data(gfx.ctx, points, gfx.ctx.STATIC_DRAW);
    a_color.data(gfx.ctx, color, gfx.ctx.STATIC_DRAW);
    gfx.ctx.drawArrays(gfx.ctx.TRIANGLES, 0, 3);
}

function drawRectangle(gfx: Graphics, position: Vec2, exts: Vec2) {
    const a_position = gfx.getAttribute("a_position");
    const a_color = gfx.getAttribute("a_color");

    const points: Array<number> = [
        position.x, position.y,
        position.x + exts.x, position.y,
        position.x, position.y + exts.y,
        
        position.x + exts.x, position.y + exts.y,
        position.x + exts.x, position.y,
        position.x, position.y + exts.y,
    ]

    const color: Array<number> = [
        1, 0, 0, 1,
        0, 1, 0, 1,
        0, 0, 1, 1,
        1, 0, 0, 1,
        0, 1, 0, 1,
        0, 0, 1, 1,
    ];

    a_position.data(gfx.ctx, points, gfx.ctx.STATIC_DRAW);
    a_color.data(gfx.ctx, color, gfx.ctx.STATIC_DRAW);
    gfx.ctx.drawArrays(gfx.ctx.TRIANGLES, 0, 6);

}

function drawCircle(gfx: Graphics, position: Vec2, radius: number) {
    const points: Array<Vec2> = new Array<Vec2>();

    const precision = 40;
    const angle = 2.0*Math.PI/precision;
    let a = 0;
    for (let i = 0; i < precision; ++i) {
        var vec = Vec2.angle(a);
        vec.mult(radius);
        a += angle;
        points.push(vec);
    }

    for (let i = 0; i < points.length; i++) {
        const current = points[i];
        const next = points[(i + 1) % points.length];
        let center = position;
        drawTriangle(gfx, [center, center.addNew(current), center.addNew(next)]);
    }
}

function drawLine(gfx: Graphics, A: Vec2, B: Vec2) {
    const a_position = gfx.getAttribute("a_position");
    const a_color = gfx.getAttribute("a_color");

    let points: Array<number> = [
        A.x, A.y,
        B.x, B.y,
    ];

    const color: Array<number> = [
        1, 0, 0, 1,
        0, 0, 1, 1,
    ];

    a_position.data(gfx.ctx, points, gfx.ctx.STATIC_DRAW);
    a_color.data(gfx.ctx, color, gfx.ctx.STATIC_DRAW);
    gfx.ctx.drawArrays(gfx.ctx.LINES, 0, 2);
}

function fullscreenCanvas(id: string) {
    const canvas  = document.getElementById(id) as HTMLCanvasElement;
    canvas.width  = window.innerWidth;
    canvas.height = window.innerHeight;
}

function draw(gfx: Graphics) {
    const position: Vec2 = new Vec2(gfx.ctx.canvas.width / 2 - 100, gfx.ctx.canvas.height / 2 - 100);

    gfx.clear(0, 0, 0, 0);
    gfx.ctx.uniform2f(gfx.getUniform("u_resolution"), gfx.ctx.canvas.width, gfx.ctx.canvas.height);
    drawRectangle(gfx, position, new Vec2(200, 200))
    drawTriangle(gfx, [new Vec2(100, 100), new Vec2(200, 100), new Vec2(100, 200)]);
    drawTriangleExts(gfx, new Vec2(200, 200), new Vec2(-100, -100));
    drawCircle(gfx, new Vec2(400, 200), 100);
    drawLine(gfx, new Vec2(100, 600), new Vec2(600, 600));
}

(() => {
    const canvasId = "game";
    fullscreenCanvas(canvasId);
    const ctx = initializeContext(canvasId);
    if (ctx === null) return;

    const gfx = new Graphics(ctx, vertexShader, fragmentShader);

    const a_position = gfx.createAttribute("a_position");
    a_position.format(2, gfx.ctx.FLOAT, false, 0, 0);

    const a_color = gfx.createAttribute("a_color");
    a_color.format(4, gfx.ctx.FLOAT, false, 0, 0);

    gfx.createUniform("u_resolution");
    
    draw(gfx);
    window.onresize = () => {
        fullscreenCanvas(canvasId);
        draw(gfx);
    }
})();