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Question: use the following javascript file and the html file to...
Question details
use the following javascript file and the html file to create a graphic by adding additional shapes by:
1) creating functions drawTriangle( vec2, vec2, vec2) and drawSquare (vec2, vec2)
- square takes the upper left and lower right as the two vec2
2) call these functions with different values to draw the shapes necessary to complete your graphic
triangle.js:
var gl;
var points;
var color;
window.onload = function init()
{
var canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
//var vertices = new Float32Array([-1, -1, 0, 1, 1, -1]);
points = [vec2(-1,-1),vec2(0,1),vec2(1,-1)]
color
=[vec4(1,0,0,1),vec4(0,1,0,1),vec4(0,0,1,1)];
// Configure WebGL
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
// Load shaders and initialize attribute buffers
var program = initShaders( gl, "vertex-shader", "fragment-shader"
);
gl.useProgram( program );
// Load the data into the GPU
var bufferId = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, bufferId );
gl.bufferData( gl.ARRAY_BUFFER,flatten(points), gl.STATIC_DRAW
);
// Associate out shader variables with our data buffer
var vPosition = gl.getAttribLocation( program, "vPosition" );
gl.vertexAttribPointer( vPosition, 2, gl.FLOAT, false, 0, 0
);
gl.enableVertexAttribArray( vPosition );
// Load the color data into the GPU
var cbufferId = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, cbufferId );
gl.bufferData( gl.ARRAY_BUFFER,flatten(color), gl.STATIC_DRAW
);
// Associate out color shader variables with our data
buffer
var vColor = gl.getAttribLocation( program, "vColor" );
gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vColor );
//setting a uniform variable for color
var uColor = vec4(1.0, 1.0, 0.0, 1.0);
var colorLoc = gl.getUniformLocation( program,
"uColor" );
gl.uniform4fv( colorLoc, flatten(uColor));
render();
};
function render() {
gl.clear( gl.COLOR_BUFFER_BIT );
gl.drawArrays( gl.TRIANGLES, 0, 3 );
}
triangle.html:
<!DOCTYPE html>
<html>
<head>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 fColor;
void
main()
{
gl_Position = vPosition;
fColor = vColor;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
varying vec4 fColor;
uniform vec4 uColor;
void
main()
{
gl_FragColor = uColor;
}
</script>
<script type="text/javascript" src="../Common/webgl-utils.js"></script>
<script type="text/javascript" src="../Common/initShaders.js"></script>
<script type="text/javascript" src="../Common/MV.js"></script>
<script type="text/javascript" src="triangle.js"></script>
</head>
<body>
<canvas id="gl-canvas" width="512" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
</body>
</html>
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