A New GI Lamp Type

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poutsa
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A New GI Lamp Type

Post by poutsa »

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Last edited by poutsa on Thu Nov 11, 2004 12:37 pm, edited 1 time in total.

wavk
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Post by wavk »

Ever heard of Ambient Occlusion?

joeri
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Post by joeri »

Actualy, you need todo it only once.
Then you can use that scene to include in new scenes.
And it's not really alot of work.
Add sphere, add spotlight, parent, duplivert, add empty, trackto empty. Done.

O, and I think wavk means it's already in blender and called Ambient Occlusiun. More on Ambient Occlusiun can be foun here http://www.andrew-whitehurst.net/tutorials.html (other 3d package used).

Dani
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Post by Dani »

indeed... AO should do the trick, and a fake GI setup isn't sooooo hard as wavk and joeri said.

but remember that AO LOOKS like GI but is NOT GI...

Dani

joeri
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Post by joeri »

???
Dani, could you please read my post again, and now don't skip the "And it's not really alot of work. " part ?

Also if you would follow the link of andrew-whitehurst in that post you would be surpriced how much Ambient Occlusion is related to fake Global Illumination.

And if Andrew is wrong, could you explain what the difference is between AO and (f)GI? I don't mean this harsh but if AO looks like GI why do i need to remember it's not?

Dani
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Post by Dani »

????

ah yes, I understand where you didn't understand...
and a fake GI setup isn't sooooo hard as wavk and joeri said.


syntax problem.

should read:

"and as wavk and joeri said, AO should do the trick and a fake GI setup indeed isn't so hard to setup"

And, I didn't say that AO is not "fake GI", I said it is NOT "GI".

Dani

solmax
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Post by solmax »

well that's what we have yafray for :) inside blender you can also use te radiosity feature together with AO.. where's the problem??

joeri
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Post by joeri »

Ai, I'd say it's a puntuation problem.
"and a fake GI setup isn't sooooo hard, as wavk and joeri said."

And, I didn't say that AO is not "fake GI", I said it is NOT "GI".
Yes, it's also not a cup of tea. But it's obvious to me why it's not a cup of tea, but not obvious why it's not Global Illumination.
So i'll repeat the questions;
could you explain what the difference is between AO and GI?
And if AO looks like GI why do i need to remember it's not?

Dani
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Post by Dani »

Hum, the light masters could explain this better than me... but I'll try to make it simple:

Global Illumination is a mixture of algorithms that take into account the tranfers of energy according to physical laws of color absorption/rediffusion/reflection/refraction/diffraction/refraction>>thus ray concentration>>caustics... basically, GI gives you : correct shadows, color bleeding, caustics, radiosity (indirect illumination)

Ambient Occlusion only generates shades according to the distances between faces... if the faces are close together they "occlude" themselves, and this generates a shade... it's a trick.
AO doesn't calculate lamp shadows (generated by lamps, sun etc... nor light bouncing nor color bleeding)
AO is a good trick to fake the standard GI scenes with grey-cloudy sky and a monument on an infinite plane... and it can do a lot more too when used with subtlety: bring your hands together: they'll get darker because the closer they are, the less light can get in between them (and the get a bit redder because of light diffusion)... AO can be used to fake this...
All in all, it's up to the user to make good (original) use of this, as always...

I hope this is clear enough (and correct enough too)

poutsa
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Post by poutsa »

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Last edited by poutsa on Thu Nov 11, 2004 12:48 pm, edited 1 time in total.

joeri
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Post by joeri »

Hee thanks Dani!
That was very clear.

philovivero
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How do I do a GI setup using spotlights?

Post by philovivero »

joeri wrote: And it's (a GI using spotlight method) not really alot of work.
Add sphere, add spotlight, parent, duplivert, add empty, trackto empty. Done.
Maybe you've done this enough times that it's obvious to you, but I can't get it to work.

I parent the spotlight to the sphere, and do dupliverts. Then I have lots of spotlights pointing in random directions. So I create an empty, and track the spotlight to the empty, but the dupliverted spotlights still point in totally random directions. So I "rot" the dupliverted spotlights to point along the normals of the sphere, and they STILL point in totally random directions. So I edit the sphere and recalculate all normals inside or outside. No change whatsoever.

Maybe it really is a lot of work?

--
philovivero

poutsa
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Post by poutsa »

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Last edited by poutsa on Thu Nov 11, 2004 12:49 pm, edited 1 time in total.

joeri
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Post by joeri »

A lot of work to find out how it works?
But I'm missing the point, you think the GI-lamp will be easy?

But you're right I forgot 1 step. Make dubli's real (ctrl-shift-a with sphere selected).
I also did not say that you should clear the rotation (alt-r) of the object assuming you work in the right view. I also didn't tell that is you use 160 lights then every light should be 1/160 of energie.
It's wise to keep the lights data-linked, so settings will be applied on all lamps.

Anyway, got a demo file here: FakeGlobalIllumium (Needs more tweaking)

poutsa
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Post by poutsa »

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Last edited by poutsa on Thu Nov 11, 2004 12:50 pm, edited 1 time in total.

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