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View Full Version : help with re-rendering an object in a scene



biliousfrog
11-27-2008, 09:57 AM
If you look at the attached image, the foreground object (Choke) plus another has been amended slightly and needs to be updated in the animation. Bearing in mind that I rendered it over almost 36hrs with 16 cores of Intel's finest, I don't really want to go through it all again unless I have to.

The amendment is that the roof has been changed to mesh (see CAD drawing) so any areas blocked by the module will now be seen.

I'm expecting the worst but does anyone have a suggestion on how I could cut the rendering times by rendering as little as possible? I'm thinking like a limited region that I could animate around the screen to render just the section containing the amended object.

...failing that, I'll render it all again. I can skip the first 30 seconds or so which will cut the time down a lot.

BTW, the camera is flying all over as modules are 'spotted' in a specific order.

Dexter2999
11-27-2008, 12:03 PM
36 hrs? It's a day and a half. It's called a "change order" and you bill for it. And they will have it by Monday afternoon at the latest if you start now.

biliousfrog
11-27-2008, 01:53 PM
yeah I know that...but if I can do it in 12 hrs I can pocket the 24 ;)

MooseDog
11-27-2008, 03:02 PM
the only thing i can think of would be to put together a series or collection of mattes for different objects to be used as alphas in compositing.

Dexter2999
11-27-2008, 06:30 PM
And next time...you will consider maybe doing those pieces that obscure parts of a scene as separate passes.

Hindsight being 20/20. I know I will start keeping that kind of thing in mind.

zapper1998
11-27-2008, 10:57 PM
How big is the scene? object size?
what are your render settings? RT or GI ?

biliousfrog
11-28-2008, 04:06 AM
Well Dexter, you're right of course but LW's native pass system makes seperate object passes a complete PITA. Maybe Janus would make things easier, I'll look into that.

TBH I don't think that there's going to be an easy way of doing it apart from re-rendering from the section that the object appears. If things were the other way round, with the mesh being replaced with a solid top, I'd just render that part of the model with some mattes for the occluding objects...but unfortunately, it isn't going to be that easy.

The scene has 960,334 polys, 1280x720, 1509 frames, raytraced shadows / reflection and RRL = 4. There's no GI, most objects have interpolated reflection blurring though, Perspective cam, 1AA, AS= 0.03, PR MB = 3 passes. DoF is done in post with After Effects lens blur. All objects were supplied as 3d AutoCAD files and converted with various apps, mostly Rhino.

Once rendered the EXR sequence is loaded into AE along with the depth pass. The sequence is paused at key intervals and information about the various modules is displayed before moving to the next. Total running length once finished is just over 3mins. There are 28 seperate modules that are 'dropped' into position and the camera moves to each location in turn (which is what makes replacements so tricky).

I'll try to post it (or part of it) when done depending on any NDA restrictions (which I am not aware of). It's a bit of a tester which will bring in a lot of future work if they're happy, which they seem to be so far.

kopperdrake
11-28-2008, 06:15 PM
Could you not produce a version of the box where the new lid is 100% white luminous and as a solid polygon and just render the sequence so you have a white shape that is essentially the lid area and the section of image you need to rerender, and the background needs to be solid black. You then end up with essentially an alpha sequence of the area you want to rerender.

Then, bring that black and white sequence into the new scene where you now have the new mesh lid. Create a polygon the same aspect ratio as your scene, attach the alpha sequence to it as a clip map and parent that polygon to your camera so that it fills the screen perfectly. When you then render you should end up with only seeing a black mass surrounding a lid-shaped hole for each frame, and that lid-shaped hole shoud contain the new image. I'm guessing that this should cut down on rendering time? You can then comp that over the original animation.

Sorry it's a bit rough but it might just work?

toby
11-28-2008, 09:26 PM
... good idea!!
that's one for the toolbox, eh?

biliousfrog
11-29-2008, 07:59 AM
Could you not produce a version of the box where the new lid is 100% white luminous and as a solid polygon and just render the sequence so you have a white shape that is essentially the lid area and the section of image you need to rerender, and the background needs to be solid black. You then end up with essentially an alpha sequence of the area you want to rerender.

Then, bring that black and white sequence into the new scene where you now have the new mesh lid. Create a polygon the same aspect ratio as your scene, attach the alpha sequence to it as a clip map and parent that polygon to your camera so that it fills the screen perfectly. When you then render you should end up with only seeing a black mass surrounding a lid-shaped hole for each frame, and that lid-shaped hole shoud contain the new image. I'm guessing that this should cut down on rendering time? You can then comp that over the original animation.

Sorry it's a bit rough but it might just work?

Genius!...but too late:D

One for the toolbox indeed!:)