View Full Version : Unseen by GI option.

05-13-2004, 02:24 PM
Not sure of the solution to this one.

One problem is spherical reflections. Can be difficult to control and get the desired effect.

Ideally what I would like to be able to do, is have say a blurred/optimised hdri image in imageworld. This would be for global illumination.

Then a hi-res detailed version, mapped onto the inside of a spherical environment which would then be used for reflections.

Currently this can't be done.

With backdrop radiosity, you get reflections, no illumination.

With monte and interpolated, you get reflections and illumination, but the illumination is coming from the spherical environment not the imageworld.

Basically there is no way to make the spherical envirionent invisible to anything other than reflections in a raytraced mode. ie unseen by GI.

Would like to see a solution this.


05-16-2004, 01:16 AM
"Unseen by rays" excludes the object from Reflections, Refractions and Radiosity.

Personaly, I never use ImageWorld for a few reasons.
- The -Z view of the image world is distorted
- Limited adjustment

I prefer to use 2 spheres with flipped polys, one for the camera
and one for the rays. The visible to camera is slightly smaller.
This allows me more control on the color, brightness of the two spheres.

"Unseen by Radiosity" is a very good idea, for many reasons.
Hopefully we will have this in the future.

05-16-2004, 02:33 AM

Unseen by rays, isn't an option though. As you want the sphere to still reflect.

Thought about the two sphere's idea, but thought this would have the same issue as with imageworld. Will have a mess around with it though.

Take your point regarding distortions.

Obviously this whole area does need attention.

This is the thread that illustrates, why more control would be handy.




05-16-2004, 07:24 AM
Hello RLM from exotic Thailand.

I introduced Unseen by Rays cause its used with the 2 spheres technique.

Small Sphere : Unseen by Rays, all shadows OFF
Bigger Sphere : Unseen by Camera, all shadows OFF

You can surface the Bigger sphere with HDR image, boost its Luminosity, change its color by Blending the surface color channel, blur it using FP_Blur on HDR_image, or anything you like.

I saw the website with Brazil. I can duplicate it easily in LW with no prob.

Good luck

05-16-2004, 08:47 PM
'Hello RLM from exotic Thailand', heh heh, that did make me chuckle.

No probs duplicating with your method. That's really encouraging, nice one.:)

There was a thread on this, over on one of the other forums, which is why I raised it here.

I shall familiarise myself with this and pass on the good news.

Thanks Panikos.


05-16-2004, 09:33 PM

I'm trying your method, but with little joy I'm afraid.

Maybe I'm not the sharpest tool in the tool box.

Smaller sphere is my reflection object, right?

Larger sphere is my GI lighting object, right?

Where I come unstuck is smaller sphere, set to unseen by rays.

If it's set to unseen by rays, then it casts no reflection. Infact it might aswell be invisible. My scene is lit by larger sphere, no problem, but this sphere is the only one to cast reflections.

Will carry on tinkering, but am running into a brick wall.

Sorry if I am being dumb.


05-16-2004, 10:45 PM
RLM, wrong :(

Please, pay some attention.

Small sphere is for Camera Only.
Big shpere is for Radiosity, Reflections, Refractions.
You cannot separate Radiosity/Reflections/Refractions.
These three are treated by LW as RAYS.

So, you have unseen by Rays & unseen by Camera.

Small Sphere : Unseen by Rays
Big Sphere : Unseen by Camera

It will help you a lot if you find the way yourself.
Otherwise I can send you a simplistic scene to play with.

But please try, and good luck :)

05-17-2004, 12:29 AM
'Please, pay some attention.' Ooh I have been told, heh heh.

Thanks for replying Panikos.

Think you are missing the whole point Panikos.

In the brazil example radiosity is separate from reflections. That's what is needed and is my issue. Separate and the ability to be selective with reflections and GI.

The optimised hdr image, which only takes up a few k, is used to generate the radisosity. The benefit, is that it is one, quicker, and two a lot smoother in it's output ie alot less noise.

That's the lighting covered, but then seperate you want a nicely defined reflection, so that's where the higher res reflection image comes in.

Presently this isn't possible in LW, as you said 'You cannot separate Radiosity/Reflections/Refractions.
These three are treated by LW as RAYS'.

Your answering a totally different question ie. How to have a different visible environment to the one used for lighting and reflections.

Pay attention dear boy. :)


05-17-2004, 12:37 AM
heh :)

First I suggest an alternative method than image-world which allows you more control.

So, to the question if you can split Reflection from Radiosity, the answer is NO (for the time being)

However, using the 2 sphere allows fine-adjustment to the Rays effect. Additionally you can control the surfaces affected using their Diffuse / Reflection channels of your reflective-surfaces.

More Diffuse = More Radiosity
Less Diffuse + More Reflection = Less Radiosity

Let me know if I can help further.


05-17-2004, 03:36 AM
Maybe I'm misunderstanding...
Object Properties -> Lights -> Exclude -> Radiosity (checked)
exclude the object from Radiosity evaluation!

05-17-2004, 04:21 AM

Object-Properties/Exclude Radiosity means that the SHADING of the object does not contain Radiosity, similarly when you exclude an Object from a Light, it means that Object shading ignores this Light.

Object Properties - Unseen by Rays means that if the object is not considered in the GI calculation. That is, if you have an Object with 250% Luminous and set it to Unseen by Rays, it will look very bright, but it wont affect the neighbouring surfaces.


I know that the two function are similar, or confusing, but they are doing two different things.

05-17-2004, 04:35 AM
Yep... you're true.

Sometimes my brain unexpectedly Shut Down! ;)