Hi
So I need to render non square pixels in Karma, and I have a camera that is anamorphic.
First thing, loading a camera from OBJ that works as intended (viewport is not squeezed in OBJ level) does not translate into LOP's with the those settings, is it because a USD Camera doesn't have a pixel aspect ratio ?

Second thing is I make a LOP's camera, and add a rendersettings node after and set aspect ratio to 2, so now my hydra viewport in Houdini GL is drawing a mask like its a x2 Pixel aspect ratio, but all things drawn as square pixels, while Karma at least does the correct squeeze on all objects.

So last thing when viewing in Karma with an aspect ratio of 2 as in this example, is there something that stretches it out so I can view it correctly like the normal Render Viewer or Mplay does, and still renders an image to disk with an non-square pixel aspect ratio
Cheers

jens_martensson
does not translate into LOP's with the those settings, is it because a USD Camera doesn't have a pixel aspect ratio ?

USD camera's don't have pixels so they don't have pixel aspect ratios, but in this case it's importing it wrong because it's not interpreting the aspect ratio of the obj camera correctly by taking the pixel aspect into account.

It can be fixed with an edit properties (camera) lop set to multiply if exists, and multiply the horizontal aperture by the pixel aspect ratio or the vertical by the reciprocal.

jens_martensson
Second thing is I make a LOP's camera, and add a rendersettings node after and set aspect ratio to 2, so now my hydra viewport in Houdini GL is drawing a mask like its a x2 Pixel aspect ratio, but all things drawn as square pixels, while Karma at least does the correct squeeze on all objects.

I noticed the aspect ratio on the render settings node is used incorrectly in the viewer. With the default aspect ratio conform policy, the image fov is expanded twice, resulting in an image of the wrong aspect ratio and double the vertical fov. I had to set aspect ratio conform policy to 'adjust pixel aspect ratio' to get an image that is the right view and squeeze. When rendering to disk or mplay it applies it correctly either way.

So to get it to render to disk correctly and also look correct in the viewport, change the aspect ratio conform policy to 'adjust pixel aspect ratio'. Keep in mind the pixel res used will directly affect the actual pixel aspect ratio.

Thanks
That works, I would hope it can be transferred more easily with an updated Scene Import, to add those properties, at least the aperture settings on the camera
Cheers

jens_martensson
Thanks
That works, I would hope it can be transferred more easily with an updated Scene Import, to add those properties, at least the aperture settings on the camera
Cheers

Yeah, go ahead and submit a bug for that. Scene import is extensible though, so maybe it's possible to fix temporarily by writing a custom husdtranslator.

I have the same problem but I am having trouble replicating the solution.
can you add the steps in a list so it can help any future readers more easily?

I've not been able to get it to work as described either.

I'm basically using different settings for the render and the viewport..

I set "Aspect Ratio Conform Policy as Crop Aperture" to "Crop Aperture".

Then for the render to disk I have "Pixel Aspect Ratio" as 2 and leave resolution as it's intended. This reads in to nuke and reformats correctly to non-square pixels.

For rendering in the viewport and mplay I again have "Aspect Ratio Conform Policy" as "Crop Aperture" set to "Crop Aperture", I leave "Pixed Aspect Ratio" as 2, and half the vertical resolution.

I'm doing this with seperate Karma LOPs. It's all way less than ideal workflow, I'm sure there must be something simple I'm missing.

Change the Aspect Ratio Conform Policy to "Adjust Pixel Aspect Ratio" and the same render settings can be used in the viewport as to disk. I think it's a bug that the pixel aspect ratio setting doesn't do anything in the viewport. Since it is ignored, the only thing you can do is use the stretch ARCP without using a different, flat resolution for the viewport.

This works if I halve the vertical aperture first.

Cheers.

rangi
This works if I halve the vertical aperture first.

Cheers.

You shouldn't need to change the vertical aperture. the aspect ratio of horizontal to vertical is the projected aspect ratio, not the film aspect ratio. For example, the scope aspect ratio of 2.35 would have the horizontal to vertical aspect ratio be 2.35, not the film aspect ratio of 1.175. At least that's how it works with USD cameras.

apparently this is more complicated than I thought, hope someone explains the steps in a list for a correct "pixel aspect ratio of 2" workflow and what version of Houdini they are using

AhmedHindy
apparently this is more complicated than I thought, hope someone explains the steps in a list for a correct "pixel aspect ratio of 2" workflow and what version of Houdini they are using

Steps:

1. Set pixel aspect to 2
   

jsmack
So to get it to render to disk correctly and also look correct in the viewport, change the aspect ratio conform policy to 'adjust pixel aspect ratio'. Keep in mind the pixel res used will directly affect the actual pixel aspect ratio.

that doesn't work for hydra viewport renders. I didn't test disk renders yet

AhmedHindy

jsmack
So to get it to render to disk correctly and also look correct in the viewport, change the aspect ratio conform policy to 'adjust pixel aspect ratio'. Keep in mind the pixel res used will directly affect the actual pixel aspect ratio.

that doesn't work for hydra viewport renders. I didn't test disk renders yet

Since the viewport doesn't seem to abide by the pixel aspect ratio, you have to set the aspect ratio conform policy to 'adjust aspect ratio,' however this has the limitation that the image aspect ratio will always be from the camera and not from the resolution.

It's not necessary when rendering to disk with husk and Karma though.

I hope this will get fixed in Houdini 20

I've found using Fill in fit mode works to get me correct aspect ratios in viewport
(D > Background tab > Camera tab)