Coding/JavsScript 삽질기2022. 1. 19. 10:25

유튜브에서본 회전 하는 3D 도넛을 구현해 보았다.

3D doughnut

코드는 아래와 같다.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>3D doughnut</title>
    <meta name='viewport' content='width=device-width, initial-scale=1.0'>
    <style>
        canvas {
            height: 100%;
            width: 100%;
        }
    </style>
</head>
<body>
<div align='center'>
    <canvas id="canvas"></canvas>
</div>
<script language="JavaScript">
    // Start: 2022.01.16
    // Update: 2022.01.18

    let cvs;
    let canvas;
    let bufCanvas;
    let bufCtx;
    let thetaX = 127;
    let thetaZ = 0;

    function InitCanvas() {
        height = window.innerHeight;
        width = window.innerWidth;

        canvas = document.getElementById("canvas");
        canvas.width = width;
        canvas.height = height;
        cvs = canvas.getContext("2d");

        bufCanvas = document.createElement("canvas");
        bufCanvas.width = canvas.width;
        bufCanvas.height = canvas.height;
        bufCtx = bufCanvas.getContext("2d");
    }

    function drawCircle(x, y, c, r) {
        if (c <= 0 || c >= 255){
            console.log(c);
        }

        bufCtx.beginPath();
        bufCtx.fillStyle = "rgb(" + c + "," + c + "," + c + ")";
        bufCtx.strokeStyle = "rgb(255, 255, 255)";
        bufCtx.arc(x, y, r, 0, Math.PI * 2);
        bufCtx.stroke();
        bufCtx.fill();
        bufCtx.closePath();
    }

    function _draw() {
        let maxSize = canvas.height < canvas.width ? canvas.height : canvas.width;
        let dimen = 8;
        let ox = canvas.width / 2;
        let oy = canvas.height / 2;

        let R1 = maxSize/20;  // 원의 반지름
        let R2 = maxSize/10;  // Y축으로 회전하기 위한 반경

        // 카메라와 스크린의 거리를 z'라 하고, 그 투영되는 상을 x',y'
        // z:x = z':x'
        // z:y = z':y'
        // x' = xz'/z, y' = yz'/z
        // z' = z1
        // x', y' = xz1/z, yz1/z
        // z의 최대거리 z2 = 5000이라 하면
        // x' <= (height/2 * 0.8) (화면 중앙 위치, 마진 0.1)
        // x 의 최대 값은 R1 + R2
        // x' = Z1(R1+R2)/z2 = height * 0.4
        // Z1 = Z2 * height * 0.4 / (R1+R2)

        let ZZ2 = 5000;
        let ZZ1 = maxSize * ZZ2 * 0.4 / (R1 + R2);

        let points = [];

        for (let i = 0; i < 628; i += dimen) {
            let x1 = Math.cos(i/100) * R1 + R2;
            let y1 = Math.sin(i/100) * R1;
            let nx1 = Math.cos(i/100);
            let ny1 = Math.sin(i/100);

            for (let j = 0; j < 628; j += dimen) {
                // Y축 회전
                let x2 = x1 * Math.cos(j/100);
                let y2 = y1;
                let z2 = x1 * Math.sin(j/100);

                let nx2 = nx1 * Math.cos(j/100);
                let ny2 = ny1;
                let nz2 = nx1 * Math.sin(j/100);

                // X축 회전
                let x3 = x2;
                let y3 = y2 * Math.cos(thetaX/100) - z2 * Math.sin(thetaX/100);
                let z3 = y2 * Math.sin(thetaX/100) + z2 * Math.cos(thetaX/100);

                let nx3 = nx2;
                let ny3 = ny2 * Math.cos(thetaX/100) - nz2 * Math.sin(thetaX/100);
                let nz3 = ny2 * Math.sin(thetaX/100) + nz2 * Math.cos(thetaX/100);

                // Z축 회전
                let x4 = x3 * Math.cos(thetaZ/100) - y3 * Math.sin(thetaZ/100);
                let y4 = x3 * Math.sin(thetaZ/100) + y3 * Math.cos(thetaZ/100);
                let z4 = ZZ2 + z3;

                let nx4 = nx3 * Math.cos(thetaZ/100) - ny3 * Math.sin(thetaZ/100);
                let ny4 = nx3 * Math.sin(thetaZ/100) + ny3 * Math.cos(thetaZ/100);
                let nz4 = nz3;

                // 법선 벡터 (nx4, ny4, nz)와 광원의 백터 내적 계산
                // 광원 위치는 (0, 0, -1)
                let lx = 0;
                let ly = 0;
                let lz = -1;
                let light = nx4 * lx + ny4 * ly + nz4 * lz;

                if (light > 0) {
                    let color = Math.round(light * 255);

                    // x' = xz'/z, y' = yz'/z
                    let xp = Math.floor(x4 * ZZ1 / z4);
                    let yp = Math.floor(-y4 * ZZ1 / z4);

                    points.push([xp + ox, yp + oy, 255-color]);
                }
            }
        }

        bufCtx.beginPath();
        bufCtx.strokeStyle = "black";
        bufCtx.fillStyle = "black";
        bufCtx.fill();

        bufCtx.fillRect(0, 0, canvas.width, canvas.height);
        bufCtx.closePath();
        bufCtx.stroke();

        points.forEach(e => drawCircle(e[0], e[1], e[2], 1));

        thetaX = (thetaX + 2) % 629;
        thetaZ = (thetaZ + 2) % 629;
    }

    function OnDraw() {
        _draw();

        cvs.beginPath();
        cvs.clearRect(0, 0, canvas.width, canvas.height);
        cvs.drawImage(bufCanvas, 0, 0);

        console.log(">OnDraw()");
    }


    function onLoadPage() {
        InitCanvas();
        OnDraw();
        setInterval(OnDraw, 50);
    }

    window.onload = onLoadPage();
</script>
</body>
</html>

 

 

Posted by chobocho

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