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TimChan

matrix in opengl and dx

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I want to ask that what is the deference of matrix operation between opengl and directx. I know one difference is that the translation vector in opengl is the last column of a matrix 4x4 but one in directx is the last row of a matrix 4x4. Is that because of the different handedness of their coordinate systems? Another question is that how to convert a opengl matrix to directx matrix and vice versa? Is just making that matrix to be transposed? EDIT: hey, why did MS make such a difference!??

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Original post by TimChan
I want to ask that what is the deference of matrix operation between opengl and directx. I know one difference is that the translation vector in opengl is the last column of a matrix 4x4 but one in directx is the last row of a matrix 4x4.

Is that because of the different handedness of their coordinate systems?


No, I'm pretty sure the handedness has nothing to do with whether the matrices are row or column major.

I'd answer the rest of your question, but I can't remember if the difference between OpenGL and DirectX matrices exists only in memory, or if it's purely a notational convention.

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Thanks for replies.

So can I get a directx matrix by making the opengl matrix be transposed or vice versa?

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So can I get a directx matrix by making the opengl matrix be transposed or vice versa?
I can't be sure about the following because I don't use DirectX. But here's what I've gathered from reading about it...

Mathematically, a DirectX matrix and an OpenGL matrix are transposes of each other. However, because the storage conventions are also transposes of each other, the matrices are actually laid out in memory the same way.

I think the vector-matrix multiplication code for DirectX and OpenGL would be the same. However, matrix-matrix mult code will be different.

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