Hi Patrick,
If I understand your question correctly, you'll want to follow these steps:
1. un-project your 2D coord into 3D space (using cam projection matrix)
2. divide the resulting vector by its 4th component (w coordinate)
3. Scale the vector so that its Z == -depth_sample
4. Apply camera transformations (if any) to go from camera to world
space (using cam transform matrix)
Hope that helps.
Cheers,
Ivan
On Fri, Nov 2, 2012 at 3:30 AM, Patrick Heinen
<mailingli...@patrickheinen.com> wrote:
> Hi everyone,
>
> I'm trying to project a point from a deep image back to 3d space. I'm
> currently taking the camera projection matrix, inverting it and multiplying
> it with a Vector 4 {pixelX*deep,pixelY*deep,deep,deep}.
> However this doesn't give me the exact position.
> When projecting from 3d to 2d the 3rd position of the resulting vector is not
> equal to the 4th position, the value changes as a function of the distance
> from camera to object and the near crop.
> To get the exact point in 3d I now need to be able to reconstruct this 3rd
> position in the vector.
> Does anyone know how it is calculated?
>
> Thanks
> Patrick
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