WebGL Lesson 03

Here are some lines of code.

var renderer = new THREE.WebGLRenderer();
renderer.setSize( 800, 400 );
document.body.appendChild( renderer.domElement );

Same code again in other style.

var renderer = new THREE.WebGLRenderer();
renderer.setSize( 800, 400 );
document.body.appendChild( renderer.domElement );

1-2-three
lesson 03

<html>

<head>
<title>Learning WebGL — lesson 3</title>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">

varying vec4 vColor;

void main(void) {
        gl_FragColor = vColor;
    }
</script>

uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;

varying vec4 vColor;

void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vColor = aVertexColor;
    }
</script>

var gl;

function getShader(gl, id) {
        var shaderScript = document.getElementById(id);
        if (!shaderScript) {
            return null;
        }

var str = "";
        var k = shaderScript.firstChild;
        while (k) {
            if (k.nodeType == 3) {
                str += k.textContent;
            }
            k = k.nextSibling;
        }

var shader;
        if (shaderScript.type == "x-shader/x-fragment") {
            shader = gl.createShader(gl.FRAGMENT_SHADER);
        } else if (shaderScript.type == "x-shader/x-vertex") {
            shader = gl.createShader(gl.VERTEX_SHADER);
        } else {
            return null;
        }

gl.shaderSource(shader, str);
        gl.compileShader(shader);

if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(shader));
            return null;
        }

return shader;
    }

var shaderProgram;

function initShaders() {
        var fragmentShader = getShader(gl, "shader-fs");
        var vertexShader = getShader(gl, "shader-vs");

shaderProgram = gl.createProgram();
        gl.attachShader(shaderProgram, vertexShader);
        gl.attachShader(shaderProgram, fragmentShader);
        gl.linkProgram(shaderProgram);

if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
            alert("Could not initialise shaders");
        }

gl.useProgram(shaderProgram);

shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
        gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

shaderProgram.vertexColorAttribute = gl.getAttribLocation(shaderProgram, "aVertexColor");
        gl.enableVertexAttribArray(shaderProgram.vertexColorAttribute);

shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
        shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
    }

var mvMatrix = mat4.create();
    var mvMatrixStack = [];
    var pMatrix = mat4.create();

function mvPushMatrix() {
        var copy = mat4.create();
        mat4.set(mvMatrix, copy);
        mvMatrixStack.push(copy);
    }

function mvPopMatrix() {
        if (mvMatrixStack.length == 0) {
            throw "Invalid popMatrix!";
        }
        mvMatrix = mvMatrixStack.pop();
    }

function setMatrixUniforms() {
        gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
        gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
    }

function degToRad(degrees) {
        return degrees * Math.PI / 180;
    }

var triangleVertexPositionBuffer;
    var triangleVertexColorBuffer;
    var squareVertexPositionBuffer;
    var squareVertexColorBuffer;

function initBuffers() {
        triangleVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
        var vertices = [
             0.0,  1.0,  0.0,
            -1.0, -1.0,  0.0,
             1.0, -1.0,  0.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        triangleVertexPositionBuffer.itemSize = 3;
        triangleVertexPositionBuffer.numItems = 3;

triangleVertexColorBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexColorBuffer);
        var colors = [
            1.0, 0.0, 0.0, 1.0,
            0.0, 1.0, 0.0, 1.0,
            0.0, 0.0, 1.0, 1.0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
        triangleVertexColorBuffer.itemSize = 4;
        triangleVertexColorBuffer.numItems = 3;

squareVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
        vertices = [
             1.0,  1.0,  0.0,
            -1.0,  1.0,  0.0,
             1.0, -1.0,  0.0,
            -1.0, -1.0,  0.0
            ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        squareVertexPositionBuffer.itemSize = 3;
        squareVertexPositionBuffer.numItems = 4;

squareVertexColorBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexColorBuffer);
        colors = []
        for (var i=0; i < 4; i++) {
            colors = colors.concat([0.5, 0.5, 1.0, 1.0]);
        }
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
        squareVertexColorBuffer.itemSize = 4;
        squareVertexColorBuffer.numItems = 4;
    }

var rTri = 0;
    var rSquare = 0;

function drawScene() {
        gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

mat4.identity(mvMatrix);

mat4.translate(mvMatrix, [-1.5, 0.0, -7.0]);

mvPushMatrix();
        mat4.rotate(mvMatrix, degToRad(rTri), [0, 1, 0]);

gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, triangleVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexColorBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, triangleVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

setMatrixUniforms();
        gl.drawArrays(gl.TRIANGLES, 0, triangleVertexPositionBuffer.numItems);
        mvPopMatrix();

mat4.translate(mvMatrix, [3.0, 0.0, 0.0]);

mvPushMatrix();
        mat4.rotate(mvMatrix, degToRad(rSquare), [1, 0, 0]);

gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexColorBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexColorAttribute, squareVertexColorBuffer.itemSize, gl.FLOAT, false, 0, 0);

setMatrixUniforms();
        gl.drawArrays(gl.TRIANGLE_STRIP, 0, squareVertexPositionBuffer.numItems);

mvPopMatrix();
    }

var lastTime = 0;

function animate() {
        var timeNow = new Date().getTime();
        if (lastTime != 0) {
            var elapsed = timeNow - lastTime;

rTri += (90 * elapsed) / 1000.0;
            rSquare += (75 * elapsed) / 1000.0;
        }
        lastTime = timeNow;
    }

function tick() {
        requestAnimFrame(tick);
        drawScene();
        animate();
    }

function webGLStart() {
        var canvas = document.getElementById("lesson03-canvas");
        initGL(canvas);
        initShaders()
        initBuffers();

gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.enable(gl.DEPTH_TEST);

tick();
    }

</script>

</head>

</html>

WebGL Lesson 03

1-2-threelesson 03

1-2-three
lesson 03