ptex from ptc?

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Priyamvad Deshmukh

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Apr 24, 2014, 5:19:49 PM4/24/14
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Hi All

I'm trying to experiment making a ptex file from a ptc file with the ptxmake tool from renderman.
http://renderman.pixar.com/resources/current/rps/ptxmake.html

This probably may not be the right space to ask this question so let me know if that's the case and ignore this question please.

I cannot find any information about what happens when one does not specify a face-edge data file to the tool. How does it decide what the connectivity information is?
Does it still filter across faces? Does it have a default connectivity logic that gets used in the process and is there a way to verify that?

Thanks a bunch
Priyamvad


Brent Burley

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Apr 24, 2014, 6:15:08 PM4/24/14
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I would expect that if you don't provide a "fedfile" ptxmake will write the ptex file with no adjacency data.  You can verify this with ptxinfo -f which will report the adjacency data.

If there is no adjacency data then the ptex api will not filter across faces.  The results may be acceptable for some uses, especially when the "clamp" border mode is used and no additional blur is added to the filter width.


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Priyamvad Deshmukh

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Apr 24, 2014, 6:43:51 PM4/24/14
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Aha, yes, it does not show any connectivity information in ptxinfo.
Cool, good to know. Thank you!!

A follow up question if I may, ptxinfo also shows no mipmap done which is also what I'd expect.
But are the in-face textures mip-mapped and filtered? Also, when creating the ptx, is there any compression applied to these in-face texture values as well?

Thanks again!
Priyamvad

Brent Burley

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Apr 24, 2014, 8:05:03 PM4/24/14
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If there are no mipmaps generated when writing the file then mipmaps will be generated on demand and added to the in-memory PtexCache.  The filter will produce an identical result, but there will likely be more I/O.

Virtually all data written to the ptex file is compressed using deflate (zlib).  Data in the in-memory cache, including generated mipmaps, is uncompressed.  However, faces with a constant value are always stored (and filtered) as a single value in the "constant data" block at the start of the file.  This is present regardless of whether mipmaps were generated.

Priyamvad Deshmukh

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Apr 24, 2014, 9:06:00 PM4/24/14
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All excellent information.

Thanks again!
Cheers
Priyamvad

Priyamvad Deshmukh

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May 20, 2014, 12:29:25 AM5/20/14
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Hi Brent

I was wondering if there is a way to create multi-channel ptex files using the ptxmake workflow?
http://renderman.pixar.com/resources/current/rps/ptxmake.html

I have multiple channels in the ptc file but ptxmake only seems to want one at a time?
Am I missing something here?

Thanks!
Priyamvad

Brent Burley

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May 20, 2014, 11:26:18 AM5/20/14
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That's more of a PRMan question, but it seems like ptxmake only accepts a single displaychannel name.  You could however write a small tool that combines multiple ptex files though.

Priyamvad Deshmukh

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May 20, 2014, 6:14:49 PM5/20/14
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Right, makes sense.

Thanks Brent!
Priyamvad

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