vignetted Zdpeth pass - ?

[simmsimaging]

I'm trying to render a zdepth pass of a basically flat terrain object and I am getting a circular vignetting in the corners in my VrayZdepth pass every time. Using physical camera, but vignette is off and the terrain is not curved to create that effect. Same thing if I render a perspective view instead of the camera. If I render with scanline and a max camera it's fine.

See attached - it's literally a flat plane that is dead-straight to camera - you can clearly see the vignette. I can't get rid of it - what am I missing?

Thanks in advance

b

[Sushidelic]

Hi Brett,

whenever you use a perspective camera pointed straight to a plane, it is normal that the corners of the image are further away then the middle part (if the distance from the middle point is z, and the distance on your plane/cam mid-point to the edge of the field of view is x, then the distance from the cam to the edge is sqrt(z² + x²) ). Just imagine a specific z-depth distance to be something like a sphere around your camera. You will get a "flat" z-channel if you use an orthographic cam that then uses parallel projection.

Hope this helps,
Michael

[simmsimaging]

That helps a lot - thought it was just me. I'll try it with an orthographic camera.

Thanks very much.
b

[vlado]

V-Ray calculates the Z-buffer as the distance from the camera position, whereas the scanline renderer calculates this as distance from the camera XY plane.

Best regards,
Vlado

[simmsimaging]

Thanks Vlado. Using a Max camera seems to have resolved it for for what I need here, which is great because I was finding that rounded displacements were getting truncated (flattened on top) with the scanline generated zdepth maps no matter how I set the range. With Vray Zdepth I hit it first time out very nicely. Probably because I can create 32bit maps, but the Zdepth ranges seem to work more a bit more sensibly in Vray. Could be just me though

b