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### #ActualKaiserJohan

Posted 12 December 2012 - 07:33 AM

Hello,

I'm not sure I understand how the triangle winding order works. I've been reading http://www.arcsynthesis.org/gltut/Positioning/Tutorial%2004.html but I don't quite understand how it works.

Specifically these lines, where the bolded I do not understand:

No matter what size or shape the triangle is, you can classify the ordering of a triangle in two ways: clockwise or counter-clockwise. That is, if the order of the vertices from 1 to 2 to 3 moves clockwise in a circle, relative to the triangle's center, then the triangle is facing clockwise relative to the viewer. Otherwise, the triangle is counter-clockwise relative to the viewer.

For reference, I'm trying to make a cube using glDrawElements, and I want to know how I should order them and why. Below is a naive attempt:

const float vertexPositions[] =
{
// front vertices
-0.5f, 0.5f, 0.0f,
0.5f, 0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
// back vertices
-0.5f, 0.5f, 0.5f,
0.5f, 0.5f, 0.5f,
0.5f, -0.5f, 0.5f,
-0.5f, -0.5f, 0.5f
};
const GLshort indexData[] =
{
// back
4, 5, 6,
7, 4, 5,
// right
1, 5, 6,
2, 1, 6,
// left
4, 0, 3,
7, 4, 3,
// top
4, 5, 1,
0, 4, 1,
// bottom
7, 6, 2,
3, 7, 2,
// front
0, 1, 2,
3, 0, 1
};


### #2KaiserJohan

Posted 12 December 2012 - 07:32 AM

Hello,

I'm not sure I understand how the triangle winding order. I've been reading http://www.arcsynthesis.org/gltut/Positioning/Tutorial%2004.html but I don't quite understand how it works.

Specifically these lines, where the bolded I do not understand:

No matter what size or shape the triangle is, you can classify the ordering of a triangle in two ways: clockwise or counter-clockwise. That is, if the order of the vertices from 1 to 2 to 3 moves clockwise in a circle, relative to the triangle's center, then the triangle is facing clockwise relative to the viewer. Otherwise, the triangle is counter-clockwise relative to the viewer.

For reference, I'm trying to make a cube using glDrawElements, and I want to know how I should order them and why. Below is a naive attempt:

const float vertexPositions[] =
{
// front vertices
-0.5f, 0.5f, 0.0f,
0.5f, 0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
// back vertices
-0.5f, 0.5f, 0.5f,
0.5f, 0.5f, 0.5f,
0.5f, -0.5f, 0.5f,
-0.5f, -0.5f, 0.5f
};
const GLshort indexData[] =
{
// back
4, 5, 6,
7, 4, 5,
// right
1, 5, 6,
2, 1, 6,
// left
4, 0, 3,
7, 4, 3,
// top
4, 5, 1,
0, 4, 1,
// bottom
7, 6, 2,
3, 7, 2,
// front
0, 1, 2,
3, 0, 1
};


### #1KaiserJohan

Posted 12 December 2012 - 07:32 AM

Hello,

I'm not sure I understand what the triangle winding order. I've been reading http://www.arcsynthesis.org/gltut/Positioning/Tutorial%2004.html but I don't quite understand how it works.

Specifically these lines, where the bolded I do not understand:

No matter what size or shape the triangle is, you can classify the ordering of a triangle in two ways: clockwise or counter-clockwise. That is, if the order of the vertices from 1 to 2 to 3 moves clockwise in a circle, relative to the triangle's center, then the triangle is facing clockwise relative to the viewer. Otherwise, the triangle is counter-clockwise relative to the viewer.

For reference, I'm trying to make a cube using glDrawElements, and I want to know how I should order them and why. Below is a naive attempt:

const float vertexPositions[] =
{
// front vertices
-0.5f, 0.5f, 0.0f,
0.5f, 0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
// back vertices
-0.5f, 0.5f, 0.5f,
0.5f, 0.5f, 0.5f,
0.5f, -0.5f, 0.5f,
-0.5f, -0.5f, 0.5f
};
const GLshort indexData[] =
{
// back
4, 5, 6,
7, 4, 5,
// right
1, 5, 6,
2, 1, 6,
// left
4, 0, 3,
7, 4, 3,
// top
4, 5, 1,
0, 4, 1,
// bottom
7, 6, 2,
3, 7, 2,
// front
0, 1, 2,
3, 0, 1
};


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