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View Full Version : Help for Radiosity-Strategy in an animation (LW2015.3)



ShadowMap
09-13-2017, 05:03 AM
Hi there Lightwavers ;-)

Although I have studied the Radiosity-Bible on this link (http://www.except.nl/lightwave/RadiosityGuide96/), I still seem to fail with the general concept when animating a GI-Scene.
The still-frame-renders look cool in my oppinion, but the animation seems to be the tricky part here.

I'm at work right now and can't get my hands on the scene file, but I'll try to post some stuff this evening.

The scene is pretty simple:
The camera stays fixed in an office-scene, desk in foreground, plant in the corner, window in the back, sunlight falling directly through the window with blinds, casting shadows on floor and wall.
Now... the only thing changing (moving) are the blinds coming down very slowly, and at the end they close, making the room pretty dark, only illuiminated by the PC monitor on the desk, some
light still spillimg through the blinds, since they don't close fully.

My questionn now is:
What's the best strategy when animating this 575 frame animation?

I know I can't bake the solution because the lighting situation constantly changes due to the blinds moving down. But I also can't cache the solution because every frame will have it's own
individual GI-pass and shading. When I check the "Animation" checkbox under Cache, something seems to go wrong; LW renders first rame only and then comes to a halt at frame 2, saying
"computing prelimenary radiosity solution).... I set the frame step for the Cache to 25 or so.... but like I said, I might be doing something completely wrong here, since it's now doesn't seem
to make any sense to cache someting, due to the constantly changing lighting situation.

Tonight, I'll post some still renders and screenshots of my settings. My research on the web didn't really help me so far bacause they all address a different situation
(e.g. objects moving, lighting remains the same all the time, camera is fixed...OR... camera is the only thing moving etc.)

Which would be the wiser approach? MonteCarlo or FinalGather?
The crucial point I guess is that the lighting situation constantly changes, making if very difficult for placing the optimal amount of sample-points (RPE's and Secondary bounces)

Any ideas?

Thanks a lot in advance for your suggestions and help ;-)

Cheers,
Steven R.

lertola2
09-13-2017, 05:50 AM
In a situation like the one you describe I think it will be very hard to eliminate the radiosity flickering. Others know better about adjusting radiosity settings but for me I have given up on interpolation. Just turn it off and tweak the Rays Per Evaluation setting. Start with a very low number like 10 or less and do tests until you find an acceptable balance between render quality and render time.

ShadowMap
09-13-2017, 06:13 AM
Thnks a lot for your quick response... I really appreciate it.
So you would go for kinda "brute-force" on this one...? I thought so, too... I guess the strategy here would be in that case; keep the RPEs low and let the Adaptive Sampling do the "hard work"...?
I could also neglect the window from being part of the Radiosity-Solution, I guess... so turning off "Use Transparency".

The bad part is also, that my Procedural Texture Bumps Maps for the walls seem very faint, almost not noticable... maybe the walls should be textured with Image Maps instead... would also maybe
gain some seconds in rendering time, since Bumps always add some extra time...

So, you're saying that interpolation always introduces flicker and "splotchies", and the only way to get rid of them is the brute-force method...?

I'll give it a try and post some pictures this evening.

But thanks so far for your input.

Cheers,
Steven R

OjN
09-13-2017, 09:13 AM
The fast solution. 2 area ligiths for the window
1 area lgith. radiosity off. blind shadows/light
1 area light. radiosity on. after the blinds (you don't want radiosity calculate blinds). diffuse on. specular off. animated intesity (faking blind effect).

A lot faster...:) Never make radiosity calculate blinds or curtains.

Cheers,
Oscar J

ShadowMap
09-13-2017, 11:16 AM
AWESOME TIPP, thanks a lot, never thought about that....... I'll give it a try this evening.
Came home, still rendering.... for another 5,5 hours.... so I can't post screenshots of my
settings right now... but I've uploaded the first frame. Later I will post my screenshot-settings,
maybe someone can see what I'm doing wrong.

BTW, I do have two polygons on a separate layer, the same size as the window glass, they emitt
light (luminosity value in surface editor, envelope from 200% down to 20% over the course of the animation.
Render time on my MacPro 2 x 2.93GHz 6-Core Intel Xeon with 12 GBs RAM: 6 minutes (720p Res.)

Rendered in linear color space and then did an exposure in Photoshop to lift up the values a bit.
But I can notice ColorBanding in the right wall.... damn!... Rendered as 24-bit TGA-File... is there a better choice???

Comments are welcome ;-)

Cheers guys,
Steven R.

Scazzino
09-13-2017, 11:37 AM
Another trick I often use is to render with the minimum DOF and also render out a Depth buffer (in OpenEXR). Then I use the Depth buffer to add further DOF blurring in post (Fusion). This helps smooth out noise so that you don't need to render quite so high samples to get rid of all the noise. It also helps smooth out some of the radiosity noise as well.

ShadowMap
09-13-2017, 05:11 PM
The fast solution. 2 area ligiths for the window
1 area lgith. radiosity off. blind shadows/light
1 area light. radiosity on. after the blinds (you don't want radiosity calculate blinds). diffuse on. specular off. animated intesity (faking blind effect).



Just wanted to try out your trick, thought it should be no big deal.... BUT where do I cancel a light from being part of the radiosity???
I see no "Exclude from Radiosity" for a light source...

Any ideas?

artzgo
09-13-2017, 05:32 PM
Just wanted to try out your trick, thought it should be no big deal.... BUT where do I cancel a light from being part of the radiosity???
I see no "Exclude from Radiosity" for a light source...

Any ideas?

https://www.youtube.com/watch?time_continue=988&v=nTbT1PX14YE

Danner
09-14-2017, 02:20 AM
In regards to color banding, there are two things you can do. One is to enable dithering in the processing tab (ctrl F8) and the other is to render to a higher bit depth.

ShadowMap
09-14-2017, 03:31 AM
Thanks very much "artzgo" and "Danner".... some VERY helpful thoughts, thanks for your help.... I'll give it a try this evening... Lightwave community is the best!!!

kyuzo
09-14-2017, 06:50 AM
Artzgo - I clicked on that link for excluding a light from radiosity, but the video is so quiet, and he's either got a heavy foreign accent, or is actually speaking a different language - I can't tell.
Any chance you have a different link or can summarise the method in a couple of sentences?

cheers,

Derek

magiclight
09-14-2017, 03:47 PM
Not sure why you can't hear it, the volume is fine in the video, but it will not help, it's not english ;)

ShadowMap
09-14-2017, 03:51 PM
There is audio in the film, but it starts later.... and yeah, I can't understand a word either (I think it's polish...),
but the main part is that you can follow what he says and you still get the concept ;-)

Cheers,
Steven R

OjN
09-15-2017, 12:14 AM
Just wanted to try out your trick, thought it should be no big deal.... BUT where do I cancel a light from being part of the radiosity???
I see no "Exclude from Radiosity" for a light source...

Any ideas?

137904

You can bake your radiosity solution without the light you don't want (about light without GI).
In this case, I believe it's not necessary. Just make the light illuminating the curtain exclude everything else.
I attach a fast experiment I did tonight. With rebound lights, fill, against window, etc.
By the way, I invite you to search for some Gerardo posts about the Fprime users tradition of use a plane for adjust the interior exposition (i use this trick in this example).

Fun,

Oscar J

ShadowMap
09-15-2017, 04:21 AM
Hi there!, Oscar ;-)

Wow, thank you SO MUCH for your help and the quick scene-setup....Man, I'm soooo stupid. In all these years I had a totally wrong concept of the procedure!
So in that case you first bake a frame of the setup and then re-use it for all subsequent frames...

But what would you do if the blinds come down, making the room darker? Would you in that case bake additional frames when the room gets darker...?
Is it actually adding further bake-solutions to only ONE cache file...? And would you then tick the "Animation" field when using cache and use the frame step...?
Is that the way to go...?

Man, but your explanation helped A LOT! Thank you so much! Wow, ccol, I can now get going with my stuff...

Cheers,
Steven R.

OjN
09-18-2017, 09:09 PM
Hi Steven,

You don't need to use the trick of bake the GI here. In this case is over-complicated.
Just use the spot light like a sun.
sky area light illuminating only the blinds and pre-blinds (exclude the interior)
sky area light post-blinds (helps the gi) with intensity animated
done. :)