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View Full Version : GI contact shadows - how to influence ?



Dirk
10-11-2008, 07:36 PM
I'm toying around with GI now, like it a lot, but I have a question:

How do I change the size / strength of contact shadows? One way seems to be to reduce diffuse on all surfaces, and increase GI intensity. What else can I do?

Here's a picture on what I'm working:

JeffrySG
10-11-2008, 10:25 PM
Well, with GI the shadows will vary based on the environment the object/ground is in. When you have very spread out light sources (like a HDRI light probe) the shadows will be very soft. When you have a very sharp strong light source (like a point light) the shadow will be very hard. You can use combos of different light sources as well. Think of the real world. It all has to do with what is illuminating the scene - or the world.

ps. very cool image! :)

SplineGod
10-11-2008, 10:58 PM
You could also try using a gradient based on distance to a null parented to the bottom of each leg. That gradient would be used in the diffuse channel/color channel to fake the appearace of a shadow on that surface.

3dworks
10-12-2008, 02:10 AM
...and don't forget the old-school trick using negative lights which in this case should be easy to setup and render very fast as well... ;)

cheers

markus

Dirk
10-12-2008, 03:52 AM
Yeah, negative point light is cool... Thanks!

Are there pits with GI I don't know about? Feels much too easy to use... and it's fast :D

Dirk
10-12-2008, 05:25 AM
Is there a way to blur the hdr probe for imageworld, in lightwave?

Dirk
10-12-2008, 06:42 AM
Don't know if that Imageworld hdr probe looks right... but nice anyway.

MooseDog
10-12-2008, 07:19 AM
Is there a way to blur the hdr probe for imageworld, in lightwave?

F6>Processing>Full Precision Blur


Feels much too easy to use... and it's fast

we have :newtek: to thank for that. i still get a little shiver, after using the radiosity cache, every time i see the "last g.i. time" zip all the way to zero seconds! definitely alot of fun to learn.

Dirk
10-12-2008, 08:06 AM
I just took a look at Exceptions Radiosity tut - So what to do with animated characters? Deformation isn't possible right now, as I understand.

Would it be an option to use GI on anything but deforming stuff, ... but how to fake GI on deforming stuff?

SplineGod
10-12-2008, 09:53 AM
The animated cache doesnt work with deformations. Also theres an issue with PRMB and caching I think...cant remember ATM.
For characters you may have to render separately and comp if you want to use the animated cache on everything else.
Its too bad they cant get it working with deformations. It certainly doesnt make the workflow easier which is what we would all like to see.

Dirk
10-12-2008, 10:50 AM
Ok, so I try to sum that up as far as I understand it now:

We need Interpolation, since without it, render times would be prohibitive when it comes to animation with radiosity.

With a static cache, only the camera can move without having errors.

When objects are animated, we need the cache for animation, however, this doesn't work with deformed objects, and the cache grows over time because new interpolation points have to be added, slowing down everything.

The growing cache and the problem with deformations seem to be fundamental problems to me - if you interpolate, you'll get those problems.

SplineGod
10-12-2008, 11:21 AM
Except on holidaysk, weekends and leapyears....its all clear as mud. :)

Dirk
10-12-2008, 04:59 PM
But radiosity cache with deformations? Is that possible at all?

And one more thing - would it be possible to compute a cache for all static parts of a scene, and drop everything else in after that - even it if means to fake the effect, like with gradients and / or (negative) lights?

CC Rider
10-13-2008, 09:17 AM
Except on holidaysk, weekends and leapyears....its all clear as mud. :)

sorry for briefly going off topic...

SplineGod, are you a Brian Regan fan?
Sounds almost like one of his routines...

:D

SplineGod
10-13-2008, 09:52 PM
I dont think Im familiar with him :)

toby
10-14-2008, 12:00 AM
And one more thing - would it be possible to compute a cache for all static parts of a scene, and drop everything else in after that - even it if means to fake the effect, like with gradients and / or (negative) lights?
It would be so much easier to render them separately and comp them together. Even if you have to comp them in LW. Or Quicktime Pro.