WebGLでハーフトーンシェーディング

<script src="js/lib/minMatrixb.js"></script>
<script src="js/script.js" type="module"></script>

//===============================================================
// GLSL
//===============================================================
const vertexShader =`
	attribute vec3 position;
	attribute vec3 normal;
	attribute vec4 color;
	uniform mat4 mvpMatrix;
	uniform mat4 invMatrix;
	uniform vec3 lightDirection;
	varying float vDiffuse;
	varying vec4 vColor;

	void main(void){

		//ライトベクトル
		vec3 invLight = normalize(invMatrix * vec4(lightDirection,0.0)).xyz;

		//拡散光の影響力
		vDiffuse = clamp(dot(normal,invLight),0.0,1.0);

		vColor = color;
		gl_Position = mvpMatrix * vec4(position,1.0);
	}
`;
const fragmentShader =`
	precision mediump float;

	//ドットの大きさ
	uniform float dotScale;

	//拡散光の影響力
	varying float vDiffuse;

	varying vec4 vColor;

	void main(void){

		//ドットの大きさを計算
		vec2 v = gl_FragCoord.xy * dotScale;
		float f = (sin(v.x) * 0.5 + 0.5) + (sin(v.y) * 0.5 + 0.5);

		//トゥーンシェーディング
		float s;
		if(vDiffuse > 0.6){
			s = 1.0;
		}else if(vDiffuse > 0.2){
			s = 0.6;
		}else{
			s = 0.4;
		}

		//ハーフトーンシェーディングで描画
		gl_FragColor = vec4(vColor.rgb * (vDiffuse + vec3(f)) * s,1.0);
	}
`;

//===============================================================
// Init & Redering
//===============================================================
window.addEventListener('load',function(){
	init();
  	rendering();
});

let canvas,gl;
let m,mMatrix,vMatrix,pMatrix,vpMatrix,mvpMatrix,invMatrix;
let prg,attLocation,attStride,uniLocation;
let torusData,tVBOList,tIndex;
let lightDirection;
let q,qt;
let count = 0;

function init(){
    canvas = document.getElementById('webgl-canvas');
	canvas.width = window.innerWidth;
	canvas.height = window.innerHeight;

	gl = canvas.getContext('webgl');
	gl.enable(gl.DEPTH_TEST);
	gl.depthFunc(gl.LEQUAL);
	gl.enable(gl.CULL_FACE);

	let vShader = createShader(gl.VERTEX_SHADER,vertexShader);
	let fShader = createShader(gl.FRAGMENT_SHADER,fragmentShader);
	prg = createProgram(vShader,fShader);

	attLocation = [];
	attLocation[0] = gl.getAttribLocation(prg,'position');
	attLocation[1] = gl.getAttribLocation(prg,'normal');
	attLocation[2] = gl.getAttribLocation(prg,'color');

	attStride = [];
	attStride[0] = 3;
	attStride[1] = 3;
	attStride[2] = 4;

	uniLocation = [];
	uniLocation[0] = gl.getUniformLocation(prg,'mvpMatrix');
	uniLocation[1] = gl.getUniformLocation(prg,'invMatrix');
	uniLocation[2] = gl.getUniformLocation(prg,'lightDirection');
	uniLocation[3] = gl.getUniformLocation(prg,'dotScale');

	torusData = torus(64,64,1.0,2.0,[1.0,1.0,1.0,1.0]);
	const tPosition = createVbo(torusData.p);
	const tNormal = createVbo(torusData.n);
	const tColor = createVbo(torusData.c);
	tVBOList = [tPosition,tNormal,tColor];
	tIndex = createIbo(torusData.i);

	m = new matIV();
	mMatrix = m.identity(m.create());
	vMatrix = m.identity(m.create());
	pMatrix = m.identity(m.create());
	vpMatrix = m.identity(m.create());
	mvpMatrix = m.identity(m.create());
	invMatrix = m.identity(m.create());

	q = new qtnIV();
	qt = q.identity(q.create());

	lightDirection = [-0.577,0.577,0.577];

	window.addEventListener('mousemove',mouseMove);
}

function rendering(){
	gl.clearColor(0.0,0.0,0.0,0.0);
	gl.clearDepth(1.0);
	gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

	const eyePosition = [];
	const camUpDirection = [];
	q.toVecIII([0.0,0.0,20.0],qt,eyePosition);
	q.toVecIII([0.0,1.0,0.0],qt,camUpDirection);
	m.lookAt(eyePosition,[0,0,0],camUpDirection,vMatrix);
	m.perspective(50,canvas.width/canvas.height,0.1,100,pMatrix);
	m.multiply(pMatrix,vMatrix,vpMatrix);

	setAttribute(tVBOList,attLocation,attStride);
	gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER,tIndex);

	m.identity(mMatrix);
	m.multiply(vpMatrix,mMatrix,mvpMatrix);
	m.inverse(mMatrix,invMatrix);
	gl.uniformMatrix4fv(uniLocation[0],false,mvpMatrix);
	gl.uniformMatrix4fv(uniLocation[1],false,invMatrix);
	gl.uniform3fv(uniLocation[2],lightDirection);
	gl.uniform1f(uniLocation[3],2.0);
	gl.drawElements(gl.TRIANGLES,torusData.i.length,gl.UNSIGNED_SHORT,0);

	gl.flush();

	requestAnimationFrame(rendering);
}

//===============================================================
// Controll
//===============================================================
function mouseMove(event){
    const wh = 1 / Math.sqrt(canvas.width * canvas.width + canvas.height * canvas.height);
    let x = event.clientX - canvas.offsetLeft - canvas.width * 0.5;
    let y = event.clientY - canvas.offsetTop - canvas.height * 0.5;
    let sq = Math.sqrt(x * x + y * y);
    const r = sq * 2.0 * Math.PI * wh;
    if(sq != 1){
        sq = 1 / sq;
        x *= sq;
        y *= sq;
    }
    if(q){
        q.rotate(r,[y,x,0.0],qt);
    }
}

//===============================================================
// Function
//===============================================================
function createShader(shaderType,shaderText){
	const shader = gl.createShader(shaderType);
	gl.shaderSource(shader,shaderText);
	gl.compileShader(shader);
	return shader;
}

function createProgram(vs,fs){
	const program = gl.createProgram();
	gl.attachShader(program, vs);
	gl.attachShader(program, fs);
	gl.linkProgram(program);
	gl.useProgram(program);
	return program;
}

function createVbo(data){
	const vbo = gl.createBuffer();
	gl.bindBuffer(gl.ARRAY_BUFFER,vbo);
	gl.bufferData(gl.ARRAY_BUFFER,new Float32Array(data),gl.STATIC_DRAW);
	gl.bindBuffer(gl.ARRAY_BUFFER,null);
	return vbo;
}

function createIbo(data){
	const ibo = gl.createBuffer();
	gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER,ibo);
	gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,new Int16Array(data),gl.STATIC_DRAW);
	gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER,null);
	return ibo;
}

function setAttribute(vbo,attL,attS){
	for(let i in vbo){
		gl.bindBuffer(gl.ARRAY_BUFFER,vbo[i]);
		gl.enableVertexAttribArray(attL[i]);
		gl.vertexAttribPointer(attL[i],attS[i],gl.FLOAT,false,0,0);
	}
}