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p0pes
04-11-2011, 09:47 PM
I feel kinda stupid but I can't seem to figure out why this isn't working. I just wanted to create an open box (cube with no top). Working off of the tutorial at http://learningwebgl.com/blog/?p=370 I edited the code to remove the top face of the cube like such. all I did was comment out the sections pertaining to the top face and then adjusted the size of the arrays. But when I run nothing draws. I'm at a loss and its probably something stupid but any help is appreciated.



cubeVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
vertices = [
// Front face
-1.0, -1.0, 1.0,
1.0, -1.0, 1.0,
1.0, 1.0, 1.0,
-1.0, 1.0, 1.0,

// Back face
-1.0, -1.0, -1.0,
-1.0, 1.0, -1.0,
1.0, 1.0, -1.0,
1.0, -1.0, -1.0,

// Top face
//-1.0, 1.0, -1.0,
//-1.0, 1.0, 1.0,
//1.0, 1.0, 1.0,
//1.0, 1.0, -1.0,

// Bottom face
-1.0, -1.0, -1.0,
1.0, -1.0, -1.0,
1.0, -1.0, 1.0,
-1.0, -1.0, 1.0,

// Right face
1.0, -1.0, -1.0,
1.0, 1.0, -1.0,
1.0, 1.0, 1.0,
1.0, -1.0, 1.0,

// Left face
-1.0, -1.0, -1.0,
-1.0, -1.0, 1.0,
-1.0, 1.0, 1.0,
-1.0, 1.0, -1.0,
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
cubeVertexPositionBuffer.itemSize = 3;
cubeVertexPositionBuffer.numItems = 20;

cubeVertexColorBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexColorBuffer);
var colors = [
[1.0, 0.0, 0.0, 1.0], // Front face
[1.0, 1.0, 0.0, 1.0], // Back face
//[0.0, 1.0, 0.0, 1.0], // Top face
[1.0, 0.5, 0.5, 1.0], // Bottom face
[1.0, 0.0, 1.0, 1.0], // Right face
[0.0, 0.0, 1.0, 1.0], // Left face
];
var unpackedColors = []
for (var i in colors) {
var color = colors[i];
for (var j=0; j < 4; j++) {
unpackedColors = unpackedColors.concat(color);
}
}
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(unpackedColors), gl.STATIC_DRAW);
cubeVertexColorBuffer.itemSize = 4;
cubeVertexColorBuffer.numItems = 20;

cubeVertexIndexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
var cubeVertexIndices = [
0, 1, 2, 0, 2, 3, // Front face
4, 5, 6, 4, 6, 7, // Back face
//8, 9, 10, 8, 10, 11, // Top face
12, 13, 14, 12, 14, 15, // Bottom face
16, 17, 18, 16, 18, 19, // Right face
20, 21, 22, 20, 22, 23 // Left face
]
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
cubeVertexIndexBuffer.itemSize = 1;
cubeVertexIndexBuffer.numItems = 30;

SteveBaker
04-12-2011, 05:52 AM
You need to adjust the numbers in the cubeVertexIndices array. When you removed those four vertices, you caused all of the vertices after that to have index values that are four smaller.

Incidentally - when you do get it working, you probably won't see the interior surfaces of the cube. Either turn off back-face culling or make more faces inside the box to represent the interior.

p0pes
04-12-2011, 11:50 AM
Yep, definite brain fart moment. Thanks.