Hi,

Does Karma expect textures to be mipmapped prior to rendering, or can it auto generate them on the fly? I see there is a "imaketx" tool that shipped with 18.5 . Do we need to use that exclusively, or will it accept .tx files generated with txmake/maketx?

Thanks,
Chris

Karma works best with mip-mapped .exr or .rat files which can be created with imaketx. For tiled, mip-mapped .exr files, you can also use tools like maketx or txmake. Karma should also work with tiled, mip-mapped .tif textures.

If you have .png or .jpg files as textures, there are two modes that karma can use to process these. Both of these modes will use significantly more memory and probably take longer for time to first pixel. So tiled, mip-mapped textures are better.

The default mode is to use OpenImageIO for texturing. There are a lot of ways to control auto-mip generation, cache, tiling etc. (see https://openimageio.readthedocs.io/en/latest/imagecache.html [openimageio.readthedocs.io] and setting the OPENIMAGEIO_IMAGECACHE_OPTIONS environment variable).

The other mode is to use Houdini's internal texture filtering, which can be enabled by setting HOUDINI_ENABLE_EXR_TEXTURE=0.

Great info, thank you Mark.

To clarify about using .pngs or .jpgs, are you saying Karma does not accept mipmapped .png files that have been processed beforehand? For example, could I run maketx on my .png texture and use the resulting .tx file with Karma?

If you run imaketx on the source .png file and create a .tx file, the .tx file will not be stored as a .png file.
And it will be tiled and mip-mapped (as a .tif file). And it will work well with Karma.

mark
The default mode is to use OpenImageIO for texturing. There are a lot of ways to control auto-mip generation, cache, tiling etc. (see https://openimageio.readthedocs.io/en/latest/imagecache.html [openimageio.readthedocs.io] and setting the OPENIMAGEIO_IMAGECACHE_OPTIONS environment variable).

The other mode is to use Houdini's internal texture filtering, which can be enabled by setting HOUDINI_ENABLE_EXR_TEXTURE=0.

Have you noticed the filtering of textures with OCIO vs Houdini native seems more broad? To get the same texture sharpness, I find I have to set filter width to 0.5 when using OCIO filtering.

I tried adding some variables as shown here to configure OpenImageIO texture cache options https://www.sidefx.com/docs/houdini/ref/env.html [www.sidefx.com]

I tried this example
OPENIMAGEIO_IMAGECACHE_OPTIONS=max_memory_MB=512.0,max_open_files=50

But after including it in my Houdini env file I get no result from rendering with Karma, cpu is definitely showing some action, but I have yet to reach first pixel on light scene after many minutes.

I have a lot of .tx files generated from Arnold, due to storage constraints, I would like to use .tx files with Karma without having a second .rat file sitting next to the .rat file.

Can I expect the same performance and first class support in Karma XPU for both? I am houdini 20.5.445 btw.