FG - questions please help me

[Cesar R]

Can someone please explain the items on the screen shot?

This is from 3dsmax 9 Mental Ray

Item #1 - controls the WEIGT of Bounces.. what does this mean?

Item #2 - I need to better understand FG POINT INTERPOLATION part of the box.

[SandmanNinja]

I think the weight behaves like a global multiplier of sorts for the number of bounces. I never use it, I just increase the bounces if I need to.

 

And I don't think any tutorial I've done covers that part of the roll-out.

 

I found this link which may help you.

http://discussion.autodesk.com/thread.jspa?threadID=540689

 

I also typed "FG Point Interpolation" (with the quotes) into google and got quite a few hits.

[SandmanNinja]

http://www.kxcad.net/autodesk/3ds_max/Autodesk_3ds_Max_9_Reference/final_gather_rollout_mental_ray_renderer.html

 

Weight—Controls the relative contribution of the diffuse bounces to the final gather solution. The value scales from "using no diffuse bounces" (value=0.0) to "use full diffuse bounces" (value=1.0). Default=1.0.

 

 

FG Point Interpolation group

These settings provide access to the legacy method of final gather point interpolation.

 

Use Radius Interpolation Method—When on, makes the remaining controls in this group available. Also makes the Interpolate Over Num. FG Points check box unavailable, indicating that these controls override that setting.

 

Radius—When on, sets the maximum radius within which final gathering is applied. Reducing this value can improve quality at a cost of rendering time. If Radii In Pixels is off, the radius is specified in world units, and defaults to 10 percent of the maximum circumference of the scene. If Radii In Pixels is on, default=5.0 pixels.

 

If both Radii In Pixels and Radius are off, the maximum radius is the default value of 10 percent of the maximum scene radius, in world units.

 

Radii in Pixels—When on, the radii values are specified in pixels. When off, radii units depend on the value of the Radius toggle. Default=off.

 

Min. Radius—When on, sets the minimum radius within which final gathering must be used. Increasing this value can improve render quality but increase rendering time. Unavailable unless Radius is turned on. Default=0.0. If Radii In Pixels is on, default=0.5.

 

 

So it sounds like a backwards compatibility option.

And the weight sounds like a 'volume control' for how much your bounces affect the scene.

[Cesar R]

great I get it now. I still need to explore the "legacy options". about the weight, its confusing, why would you want 4 bounces that only affect the scene .5 or 1/2 as much, wouldn't you rather just have 2 bounces?

[Justin Hunt]

Its one setting that 99.9% of the time you can quite safly forget about, so I would loose any sleep over it

 

The point interpolation methode was brought in to "simplyfy" the workflow. Once again most of the time you can use this methode over the "legacy" methode. Where it is benificial, sometime you will get artifacts (I call then mold patches as this is what they look like) with the point interpolation methode. Using the other methode doesnt get these artifacts. However it can be a bit time consuming finding the right numbers.

 

jhv

[SandmanNinja]

MAYBE (and this is a guess) if you have Bounces: 4 and set it to 0.5 Weight, MAYBE it will still bounce the photons 4 times, but maybe only half of the number of photons?

 

If I have an interior that has lots of nooks and crannies, it might take 4 bounces to get some photons into all of those tight places. But then you may not want all of the photons bouncing that much.

 

(If this was the case, just decrease the number of photons..?)

 

But like Justin said, don't lose any sleep over it.

[Cesar R]

Ninja, it makes sense, maybe you need many bounces, but you dont need them to light the scene 100% thus making it brighter. Maybe you just want the light to distribute evenly?

[SandmanNinja]

yeah that's my thoughts.

 

But like I said, none of the 2318 lighting tutorials I've done over the last 6 months have mentioned it (at least, it felt like that many tutorials! hehe).

[Cesar R]

um. okay, thanks !