Issue #1285009636


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Message number: 1285009636
Synopsis: Clamped Z-Depth
Last posting date: 2010/09/28 11:32
Last answer date: 2010/11/19 10:03
Categories: Support - Vue 8.5 xStream - Solving a software issue
Posted by:ben p
On:2010/09/20 12:09:38
Operating system:MacOS X 10.5
Desktop resolution:1920x1200
Color depth:32 bits (millions of colors)
Video board model:ATI Radeon 4870 1GB
Video driver reference:EFI Driver Version: 01.00.318
Product version (and build #):vue xstream 8.50-04 Build 52340

When I render a Z-Depth pass or a Distance to Camera pass, my depth information is clamped to some values between .633 and 1.0. The sky is 1.0 and the closest I can get to camera is around .63. I am outputting 32 bit floating point EXRs. Is there any way to get the full range of values from 0-1? Thanks.

Posted by:Lee Randall
On:2010/09/21 06:25:54

Hi ben,

Have you tried changing your OpenGL clipping settings (Options panel>Display tab)?

Best regards.
Lee Randall

Posted by:ben p
On:2010/09/27 17:30:53

Thanks for the reply. I changed the OpenGL clipping as per your instructions. While this setting affects the viewport display, it doesn't seem to affect the Z-Depth render pass at all. The .EXRs I am outputting are still clipping. It looks like no matter what, the Z-Depth is being evaluated with 0 distance being somewhere behind or at the camera position, instead of the closest visible point as 0.
We are compositing Vue renders with renders out of Renderman, so what we will have to end up doing is clipping the Renderman depth to the same values as the Vue depth, which is pretty limiting and will throw away more than half of the Renderman depth info.
Any other ideas?

Posted by:Lee Randall
On:2010/09/28 07:17:57

Hi ben,

I'll have to check with the developers

Best regards.
Lee Randall

Posted by:ben p
On:2010/09/28 11:32:59

Thank you.

Posted by:John Canver
On:2010/10/20 11:03:05

Hi ben,

Z-depth information is coded using a logarithmic rule, to give better precision for near distances. The distance is absolute, because making it dependent on closest/farthest hit objects would make it impossible to compare z-depth channels for different renders.

the MAXDEPTH encoded is 100,000. To get the linear distance value from the z-depth channel, the following formula is used:

depth = exp( u * log( 1 + MAXDEPTH ) ) - 1

where u is the normalized z-depth value (z/255 in 8-bit format, z/65535 in 16-bit format, and so on)

Best regards.
John Canver

Posted by:E-on software support
On:2010/11/19 10:03:05

This support ticket was closed automatically for lack of response.
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