DirectXMath: XMMatrixPerspectiveFovLH AspectHByW?

[nlguillemot]

There's no github for DirectXMath, so I guess this is the next best thing.

I think the AspectHByW parameter of XMMatrixPerspectiveFovLH should be AspectWByH.

If you look at the math to compute m[0][0] and m[1][1] inside XMMatrixPerspectiveFovLH, you'll see that it's identical to the math used in gluPerspective. However, gluPerspective's aspect parameter is width/height.

How could gluPerspective and XMMatrixPerspectiveFovLH use the same math, but have a different meaning? Futhermore, the results in my app look wrong when I pass height/width, but look correct when I pass width/height.

[walbourn]

The first thing to say is that gluPerspective should be compared with XMMatrixPerspectiveFovRH, not LH because all OpenGL math is generally column-major, right-handed.

You are correct that the aspectRatio should be W / H as documented on MSDN. The name AspectHByW is confusing so it should probably just be changed to AspectRatio

[walbourn]

Note that I've been considering a DirectXMath GitHub for some time. I'll see if I can make that happen this year...

[walbourn]

There is now a DirectXMath GitHub. I've created this issue there.

[nlguillemot]

Nice! Well done on making it happen.