Question by teexit · Jun 28, 2013 at 08:03 AM · transform coordinates matrix

How to transform a viewport point to homogenous coordniate?

Hi guys,

Unity can use Camera.ViewportToWorldPoint to transform point to homogenous coodinate.

But, if I don't want to use this function how to do this by matrix?

Thanks a lot.

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moonstruck · Jun 28, 2013 at 08:18 AM 1

Camera.ViewportToWorldPoint doesn't return the homogenous coordinates. It returns usual cartesian world coordinates of the point (x, y, z), where (x, y) are normalized coordinates (both components are in [0,1] range) on the camera plane and z in the distance between the camera and that plane along camera's forward direction.

So what matrix do you need?

teexit · Jun 28, 2013 at 08:28 AM 0

moonstruck, thank you for reply. Actually, I need the inverse of view-projection matrix. But, I can get this... Unity can get projection matrix(but, this matrix is opengl conversion)

moonstruck · Jun 28, 2013 at 08:45 AM 0

http://docs.unity3d.com/Documentation/ScriptReference/Camera.html

So it may work you: ( camera.projection$$anonymous$$atrix * camera.cameraToWorld$$anonymous$$atrix ).inverse (projection coordinates into the camera view space).

teexit · Jun 28, 2013 at 09:43 AM 0

But, document say "that camera space matches OpenGL convention". If I run on directx version, is it still work correctlly?

moonstruck · Jun 28, 2013 at 10:11 AM 0

Yeah, because it is the convention for this particular matrix (i.e. the orientation along z axis). It shouldn't depend on the library you are using.

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