Global Illumination Assistance...

Chris2005

I'm trying to get light bounces like in this shot:


I'm using FinalRender's GI... However, I'm trying to figure out how I can increase the intensity of the light bounces without increasing the GI over the whole scene, which just brightens everything...

Any insight would be greatly appreciated.

Coolhand

not so long ago it would be common practise to simply add extra lights to simulate the effect... It's possible the effect you see there is "faked" rather than actual GI. For example the blue fill lighting is most likely just that, fill lighting - possibly an "area" light as opposed to a point source.

to do it properly, try working with realistic lighting, materials and exposure levels and experiment with angles and geometry... remember the larger the surface area more photons will be produced for a given value. and angle of incidence is all important to the reflected lights intensity on another surface (in real life of course all types of reflectors are sometimes used to help fill in miniatures) IRML is far better at lighting these shots than me so maybe he or someone else can help you further.

Chris2005

Coolhand wrote: »

not so long ago it would be common practise to simply add extra lights to simulate the effect... It's possible the effect you see there is "faked" rather than actual GI. For example the blue fill lighting is most likely just that, fill lighting - possibly an "area" light as opposed to a point source.

to do it properly, try working with realistic lighting, materials and exposure levels and experiment with angles and geometry... IRML is far better at lighting these shots than me so maybe he or someone else can help you further.

Yea, I myself have faked the effect in scenes before by using extra lights, haha.

Well, I'm having a hard time determining if there's any special finalRender material I need to use... finalRender comes with a lot of materials for doing a lot, but I'm not sure which one to use, well, some obviously aren't gonna be used, since they're simply not the right materials, e.g. right now, I'm just using regular standard materials in Max...

Here are the materials:


I'm thinking Advanced maybe... since it seems really robust... in the past I've used it, I use it to brighten the warp nacelle core on Prologic9's Enterprise D... which when a blurry refraction is placed on the grill "casing" it allows the core to stay brighter... it's worked great in that regard, but I've never used the material on anything else...

Chris2005

Yup, solved it.

Using finalRender's Advanced Material.





Some artifacts, like around the forward windows by the deflector dish area, because, well the whole model isn't there yet.

Coolhand

OK so the issue was a non-realistic material, or a material you really shouldn't be using with that renderer... As a rule, if you're going for realism, never use the 'standard' materials, they're as old as the software itself.

Chris2005

Coolhand wrote: »

OK so the issue was a non-realistic material, or a material you really shouldn't be using with that renderer... As a rule, if you're going for realism, never use the 'standard' materials, they're as old as the software itself.

Yea, even with the fR-Advanced material, I had to bump up the material's "GI send" amount... default at 1.0... in these renders it's 25.

Coolhand

I really can't advise you any further as i don't know this renderer, but I'd say normally with these types of settings if you start at 1 and end at 25, you're possibly doing something wrong.

IRML

what you're telling the material to do is trick the GI into emitting 25x more light than it receives for that surface, you shouldn't be increasing the intensity like that, from your test renders it looks like the bounce light is now as bright as the key light, which clearly looks wrong, you must leave it at 1.0 to maintain physical accuracy - a surface cannot emit more light than it receives

(add to that it will be a nightmare for continuity with other surfaces or objects in the scene)

look at the screenshot, the key light is clearly very bright and is coming almost straight down so it covers more of the ship, the combination of brightness and higher coverage is what's casting the bounce on the bottom of the nacelles, you should be able to do this fine with standard materials if you at least make some effort to duplicate their setup

Chris2005

The Cebas Wiki gives a nice short description and in depth explanation of each setting for this material... unfortunately, you have to register to access the Wiki, so this is just 411...

What they say about these particular controls for this material is:

This group of controls determines how the materials within your scenes react when Global Illumination is used. These controls only set the per-material properties, and do not activate GI by themselves. You will still need to activate the Global Illumination from the renderer rollouts.

However, for the "Send" spinner:

This spinner provides a multiplier value that increases or decreases the intensity of transmitted Global Illumination data from objects using this material. This is a quick way to boost the intensity of the GI effect for specific objects in your scene.

Send = 0.5..................................Send = 2.0

Here is a render with all the materials "GI send" set to the default 1.0, and the key light is set to 1.0:


Here is the same render, only difference is the key light is set to 10.0:




I can see the light bouncing onto the pylon, but not as intense as images from my previous post... so is this one of those scene by scene type things?

IRML

yeah so it's what I said it was, if you want my advice don't use things like that, if you want to do a little tweak I think it would be better to add a light like coolhand suggested

your keylight of 10 looks much better but you still haven't matched the direction in the screenshot, also remember you've got no nacelles to catch the bounce light, which themselves would then make further bounces

Chris2005

IRML wrote: »

yeah so it's what I said it was, if you want my advice don't use things like that, if you want to do a little tweak I think it would be better to add a light like coolhand suggested

your keylight of 10 looks much better but you still haven't matched the direction in the screenshot, also remember you've got no nacelles to catch the bounce light, which themselves would then make further bounces

Yea, I've used that light trick before.

Awesome. Thanks.

My one question is, I've seen shots with that kind of GI bouncing, but the scene's lights never blow out the ship... how?

Coolhand

If they aren't doing fakery, and they probably are, I think the trick to that shot is that you're never looking at a directly lit surface, so the key light is behind or at a shallow angle of incidence to all the visible geometry... if you were looking directly at a directly lit surface in that example shot it would all be blown out with the same exposure settings that you're using to shoot it from the underside/opposing the key light... so that gets more mileage out of the bounces because the relative intensity is higher to begin with. There are obviously additional bloom effects too which must be brightening up the darker areas near the brightly lit areas, you need to add this also or you won't get the right effect. you also need to increase your fill lighting to match the original better and this will also supplement the bounced light...

so to sum up you really at a minimum have 3 factors lighting or brightening the indirectly key lit surfaces:

fill light (again probably a big area light underneath, your fill is too dim)
bounced key light (your key light is probably too dim / exposure is wrong)
bloom of the key lit areas. (you seem to be missing this entirely)

and there may also be even more lighting, compositing fakery going on.

oh, i also forgot a really important thing, actual reflections on the actual surfaces themselves, the ship here clearly has a fairly shiny hull, which again will add to the bounced effect as some surfaces are also being brightened by reflection of other lit surfaces, it may be reflecting a planet below it too.

Chris2005

I see what you're saying.

Yea, you can see the shot in this trailer at 56 seconds in...

Yea, I plan on working on the lighting a little more once I get the whole model converted... it's hard to do proper lighting on an incomplete model.

Melak

Well in that shot, the parts of the ship in direct light do look pretty blown out

Chris2005

Here's a render, when I combined the secondary hull with the saucer:


Actual animation render coming soon...

Melak wrote: »

Well in that shot, the parts of the ship in direct light do look pretty blown out

Yea, but I've seen shots before, can't recall them exactly, where the light isn't blowing out the image, but there is still considerable light bounce...