pockets Posted January 16, 2016 Share Posted January 16, 2016 Hey there, I've recently run into an issue on two shots where the standard Alembic Archive doesn't seem to import an animated focal length on any camera objects. It's never come up before since zooming is pretty rare. I thought it was an issue with the file coming from Soft, since aperture and pixel aspect ratio aren't interpreted correctly but that's an easy fix. But I've loaded the Alembic into Maya and I get a camera with zoom during the shot intact, where Houdini just has a fixed focal and no animation. I exported the camera from Maya to a separate Alembic and this too reads into Houdini with a fixed focal length. Before I put the bug report in and try to figure a workaround I wanted to see if anyone else had run into this issue. There aren't many parameters to the Alembic Archive so I feel safe assuming this is a bug and not simply operator error. cheers Quote Link to comment Share on other sites More sharing options...
fathom Posted January 16, 2016 Share Posted January 16, 2016 are you saying there are no expressions in the alembic camera in houdini? the focal, aperture, near/far, and window parms should all have expressions that query the alembic camera dictionary -- regardless of whether there is animation in the alembic file. if those are intact, then what is the focal/aperture you're getting? it's gotta come from somewhere -- does it match any of the frames? does the camera animate in any other way or is it locked off? check the maya camera and see what parms are changing and make sure they're something normal that houdini will understand -- ie, it's not faking a zoom with some other esoteric camera controls. Quote Link to comment Share on other sites More sharing options...
pockets Posted January 16, 2016 Author Share Posted January 16, 2016 (edited) The camera animates and a static focal and (bogus) aperture are read in. On shots with a static focal length it's always been correct, to the best of my recollection, but there's a single held value that's, I'm assuming, a single value in the source camera's zoom range. Also, it's not being animated in Maya it's being animated in Softimage and I read the Alembic into Maya as a control, to see what it did there. Maya correctly interprets the animated focal length. Houdini is not, I only get a single value. And, from the Alembic scene which Maya was able to read correctly I wrote that camera out and Houdini treated it exactly as it did the camera coming from Soft, with no animation in the focal length, only a single value. edit: and actually, no, there are no expressions if I dive down into the hierarchy within the Alembic Archive to the Houdini camera object. There are all static values and the only expressions are on the various Alembic Xform SOPs, which has been my experience since H13. The quality of the parameters in this camera has varied depending on where the the Alembic was written from. Softimage in writing bogus pixel aspect ratios into the file which Houdini interprets a little differently than Maya, and the aperture is completely wrong but that's an easy override. An animated focal, however, is a little more fiddly. Edited January 16, 2016 by pockets Quote Link to comment Share on other sites More sharing options...
fathom Posted January 16, 2016 Share Posted January 16, 2016 sorry, but i'm not sure that totally answers my question. are the focal/aperture on your camera coming up as expressions (python code grabbing alembic dictionary info) or are they simple constant values? has the camera's import frame somehow come undone? the camera has to import its view data separately from the transform that positions the camera, so it's possible the camera is looking at frame 1 or something whereas the xform is pulling the right data. Quote Link to comment Share on other sites More sharing options...
pockets Posted January 16, 2016 Author Share Posted January 16, 2016 No, there are no expressions on the camera node at all. It has static values in all parameters. The only expressions of any kind present in the entirety of the Alembic Archive hierarchy is in the Frame and Frames Per Second parameters on the Alembic Xform node containing the Houdini camera SOP. No Python anywhere. However, that was H15.0.313 and I just read the Alembic into H14.0.474 and not only does the camera successfully zoom but all the pertinent camera back parameters have expressions. Aperture and pixel aspect ratio are completely wrong but I have a fix for that. So, I'll look at versioning up to the next production build soon and perhaps in the meantime "launder" the files through H14. Quote Link to comment Share on other sites More sharing options...
fathom Posted January 17, 2016 Share Posted January 17, 2016 wow, weird. i'd def submit that as a bug. Quote Link to comment Share on other sites More sharing options...
pockets Posted January 17, 2016 Author Share Posted January 17, 2016 If it's still borked in the next release version I install I will. They're already up to 15.0.347 so, since it wasn't broke before I'm hoping I'm just stopped at an unfortunate version. It was an oversight on my part not recognizing that the camera back parameters were without embedded expressions. All of the other shots with fixed focals worked and were aligned just fine so I wasn't thinking something was quite that broken. Not to mention, this version of Soft has some issues with its Alembic export. Even Maya misinterprets some of the parameters, but it's one of those not always and not in the same way sort of thing. The kind of problems I hate. We've been able to get over it by comparing the cameras in both packages side-by-side. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.