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65 lines (51 loc) · 1.61 KB
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TranslatedTriangle.js
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65 lines (51 loc) · 1.61 KB
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var VSHADER_SOURCE =
'attribute vec4 a_Position;' +
'uniform vec4 u_Translation ; '+
'void main(){' +
'gl_Position = a_Position +u_Translation;'+
'}';
var FSHADER_SOURCE =
'void main(){gl_FragColor = vec4(1.0,0.0,0.0 ,1.0);}';
var Tx = 0.5,Ty = 0.5,Tz = 0.0;
function main(){
var canvas = document.getElementById('webgl');
var gl = getWebGLContext(canvas);
if(!gl){
console.log('Failed to get the rendering context');
return;
}
if(!initShaders(gl,VSHADER_SOURCE ,FSHADER_SOURCE)){
console.log('Failed to initialize shaders');
return;
}
var n = initVertexBuffers(gl);
if(n<0){
console.log('Failed to set the position of the vertices');
return;
}
var u_Translation = gl.getUniformLocation(gl.program, "u_Translation");
gl.uniform4f(u_Translation , Tx,Ty,Tz , 0.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0 , n);
}
function initVertexBuffers(gl){
var vertices = new Float32Array([
0.0,0.5,-0.5,-0.5,0.5,-0.5
]);
var n = 3;
var vertexBuffer = gl.createBuffer();
if(!vertexBuffer){
console.log('Failed to create the buffer object');
return -1;
}
gl.bindBuffer(gl.ARRAY_BUFFER , vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER , vertices , gl.STATIC_DRAW);
var a_Position = gl.getAttribLocation(gl.program , 'a_Position');
if(a_Position <0){
console.log('Failed to get the stroage location');
return -1;
}
gl.vertexAttribPointer(a_Position , 2,gl.FLOAT , false ,0,0);
gl.enableVertexAttribArray(a_Position);
return n;
}