CGTalk - How do I grow the render area without changing elements' size?

View Full Version : How do I grow the render area without changing elements' size?

juanxer

01-19-2009, 09:31 PM

I have done an old-style multipass-heavy job (duplicating projects and adjusting things, the usual). Now I find that, althought the animation I did is quite fine, I' must reduce the size of the objects in the frame. I can scale them all in After Effects without problems, but some elements (reflections and shadows) got halfway off the frame, so i have a problem to solve, and it's not as simple as a re-render.

EIAS allows one to crop the render area. Well, I wish it would allow for negative croppimg values (acting like printing apps' "bleeding" values) to cover more of the scene without accidentally changing the scene elements' size in pixels.

How do you deal with this (other than the obvious "cover your ass by rendering bigger than the final frame so that nothing gets cut off and you can reposition and resize later)?

scimmo

01-20-2009, 02:31 AM

I just answered this in the EI forum- and now, after reading your post here, I think I have a better idea of what you're up against.

My suggestion is the same, though- just enlarge your resolution settings but keep your camera's focal length the same. It should work fine. We do this all the time when going from SD to HD.

Scott

juanxer

01-20-2009, 06:58 AM

Mmmm, if I change resolutions, certainly the FOV data changes accordingly, too. If I change FOV then back to what it was, would I get what I want? I'll test it as soon as possible.

(This is a lifesaver. Thank you!)

richardjoly

01-20-2009, 03:16 PM

I don't know if this what you are looking for but the way I understand it is you have the inside image of my example and want the larger one.
The small one is 600 pixels wide and the large one 1200. To get the same aspect you have to change the focal length to expand your field of view. Twice the size, half the focal length.

Project is here:
http://www.rdn.qc.ca/eias/bleed.zip

scimmo

01-20-2009, 06:01 PM

Richard's method works great if you want to expand all borders. My suggestion works if you want to just expand the width (focal mode is horizontal). I think Richard's method is probably more what you were looking for?

Here's a couple of images to show what I was saying...

Scott

richardjoly

01-20-2009, 07:02 PM

Most interesting Scott. Never thought of doing it like that. I was under the impression it would change the perspective of the objects...

We now have crop, bleed would be a nice addition...

scimmo

01-20-2009, 08:35 PM

IMHO, if you need to "patch" a render with a new one- let's say you're going to comp it all in AE- then you need to have two things: the objects have to be the same size or you get mismatches in the anti-aliasing; and the angle has to be the same.

There's a couple of ways to skin a cat, as they say.

juanxer

01-20-2009, 09:12 PM

These solutions are all mightily interesting. Thank you all for that, both here and at the EITG forum.

A Freehand/Illustrator-style "bleed" feature would be the less complex way for an user to control this, anyway. Has any other 3D app anything like that?

What happened to me with this project must be the silliest "gotcha" one can get. :banghead: :)

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