Caustics?

Started by helentr, March 20, 2007, 03:06:07 am

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helentr

Fooling around, I came with this image.
The red part of the shadow of the left sphere looks like caustics. Since that is not possible in Terragen AFAIK, I wonder what it is. Transparency, reflection, GI?

Helen

RealUser

I would say this is simple transparency or translucency. No?
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DiscoBall

Translucency or Luminosity.

Coupled with high reflectivity, it can produce that :P

Found out when texturing my plane in TG2 today ^ ^

rcallicotte

Sort of like this...sort of.
So this is Disney World.  Can we live here?

MeltingIce

It's most likely the global illumination.  The way GI works is that it bounces light rays off of objects, and takes that object's properties with it.  So when the sunlight bounces off of that red sphere, it casts a reddish glow on the ground.  Luminosity greatly increases this effect, since luminous surfaces actually emit a little light.

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helentr

It could be the global illumination, but I have never seen it so intense before. Even once when I had set GI to extreme values, I only had weak shadows.
There is no reflective shader or transparency or luminance in the scene. I did not change anything from the defaults, except for the render settings. I find it a little eerie  ;)

Helen

DiscoBall

Check your models :p

Maybe the models had high reflective properties/textures already?

helentr

DiscoBall,

The model (which is uploaded) has specular/reflectivity of 1, which is not too much (or too little) I think.
But this scene is strange in other ways. It occasionally crashes on opening and, every time it is rendered, the results are different.
In this render the "caustics" has moved to another sphere and the lighting on the objects has changed (and it is the same TGD with no changes)

Helen

Mohawk20

I still think it has something to do with the GI...

As we have seen in the past, the GI system has a mind of it's own, allways rendering scenes different. Oshyian warned about GI in animations, giving different lighting in every frame, or even with cropped and stitched images. Or what about the red renders?? Those are still showing up too, abort and render again, nothing is wrong.

Just this afternoon I had a render of a vulcanic scene. I had a dark gray base layer, a bright red voronoi pattern surface layer, and a white ash layer. On one of the 10 cropped renders I made (800x600 had to be rendered in 2 halves....) the red layer suddenly had all these orange spots. Rendered again nothing wrong.

All this points towards GI randomness, in this scene too.
Howgh!

Will

I also agree with the others, I'm guessing its a GI thing.

Regards,

Will
The world is round... so you have to use spherical projection.

Oshyan

Yep, almost certainly GI-related. The GI system is still in need of a lot of fine-tuning. It will get more accurate and probably faster as well with further development. But keep in mind it's still a landscape-focused GI system, intended to work particularly well with atmospherics. It's never going to be a candidate for a good result on the "Sponza Test". But you'll be hard pressed to find a better outdoor GI solution. :)

- Oshyan

Cyber-Angel

Could some one test the TG2 render using the Cornell Box Method as I would like to see the results, and would show up areas that need refinement.

Regards to you.

Cyber-Angel

Oshyan

The Cornell Box is largely irrelevant for the same reason that the Sponza test is - the GI system is focused on looking good (and rendering at reasonable speed) over large landscapes and complex atmospheres. It's not designed to work well in that kind of closed environment. Conversely if you took a general purpose GI solution and threw a TG-equivalent landscape scene at it, it would either choke or produce inferior results. It may be possible to "dual-tune" the GI system in the future to allow for great rendering of enclosed interiors as well as landscapes, but TG's real focus is on landscapes, plain and simple, so that's not going to be a priority.

Not to mention that TG2 doesn't have transparency yet so the Cornell Box would be impossible to properly reproduce. ;)

- Oshyan

DiscoBall

Ah I see...
no wonder the red shading was different in each picture...

helentr

So the verdict is GI. Thank you.
I am beginning to visualize Terragen GI better - it is a little different from the POV-Ray one.

Helen