Why use skydomes, when you can just use a white backdrop?

[Holger]

I often read about white skydomes, and how nice it looks using them. I have tried it myself, but I have a question. Why do people use skydomes when you can just set the backdrop to white and get what appears to be the exact same effect?

[tijgervisuals]

One reason is that with a white backdrop you get even lighting in radiosity.
With a skydome of some kind you can 'play' with the color and luminosity of the polgons to create a more 'lifelike' lighting....

my 2 eurocents :)

[Holger]

Ah, I guessed that was the reason. But all my attempts to make a more realistic skydome, results in exactly the same lighting and shading as with a backdrop. The only diffirence is how bright or dark the lighting is, but the shadows has exactly the same shape and placement.

Can you, or others, give me examples of "a better skydome"?

:)

[Exper]

Little help here:
Skydome generator for rendering
http://vbulletin.newtek.com/showthread.php?s=&threadid=16852&highlight=skydome

[marble_sheep]

Just an idea... couldn't you create a large, low-poly half-dome, convert the polys into luxigons, and then in Layout convert the Luxigons into area lights? That would solve the reflection and refraction issues of a light dome, but it would have more control than a white backdrop. The only drawback might be increased rendering time. I've never actually tried it, I'm just throwin' out ideas.

[Holger]

Originally posted by marble_sheep
Just an idea... couldn't you create a large, low-poly half-dome, convert the polys into luxigons, and then in Layout convert the Luxigons into area lights? That would solve the reflection and refraction issues of a light dome, but it would have more control than a white backdrop. The only drawback might be increased rendering time. I've never actually tried it, I'm just throwin' out ideas.
I have discovered that a "box" of giant arealights around an object creates about the same effect as a skydome. The rendertime is not too bad. Maybe that is a good solution.

[Brett H.]

Funny, that idea has been used about as long as area lights have existed in LW. It's great for a GI look without killing render times (before Fprime, that is).

[Jamel]

how does that skydome thing work in the first place were do u put the dome when ur done

[marble_sheep]

Originally posted by Brett H.
Funny, that idea has been used about as long as area lights have existed in LW. It's great for a GI look without killing render times (before Fprime, that is).

Nobody here was claiming to have invented it or anything, we were just discussing all the different ways to accomplish the same task, and the benefits of each. Also, there are some situations where taking the time to fake radiosity takes longer than actually using radiosity. Other times, you are right, it's easier to fake it.

how does that skydome thing work in the first place were do u put the dome when ur done

A skydome is a giant half-sphere, with the poly flipped inward and a luminosity value applied to the surface. When radiosity is activated, the dome casts a very diffuse light.

[Exper]

Originally posted by Holger
I have discovered that a "box" of giant arealights around an object creates about the same effect as a skydome. The rendertime is not too bad. Maybe that is a good solution. This is a good workaround.

Another good one is the Textured Environment (using a Gradient) + Backdrop Radiosity.

I previously provided a link where we discussed a little about the limitations of SkyDome technique...
requesting a new SkyDome Light Type
(any suggestion, feedback or comment is very welcome).

[Holger]

Originally posted by Exper
Another good one is the Textured Environment (using a Gradient) + Backdrop Radiosity.

I previously provided a link where we discussed a little about the limitations of SkyDome technique
Yes, I read the thread. Thanks for the link. :)

[Brett H.]

Originally posted by marble_sheep
Nobody here was claiming to have invented it or anything, we were just discussing all the different ways to accomplish the same task, and the benefits of each. Also, there are some situations where taking the time to fake radiosity takes longer than actually using radiosity. Other times, you are right, it's easier to fake it.
No, you misunderstood. I wasn't saying "wow, they think this is a new idea", I just thought it funny (ha ha) to think that people have been attempting to fake the GI thing with area lights for so long. No offense meant, and none taken.

[gerardstrada]

I use TGALH (The Great Textured Area Light hack) of Court Jester for these packs:

http://www.geocities.com/gerardstrada/pruebaglo1.txt


http://www.geocities.com/gerardstrada/pruebaglo3.txt


http://www.geocities.com/gerardstrada/pruebaglo2.txt


I use it all the time and I think is much better than conventional Skydome.
Here the link:
http://www.altyna.com/lw/specrefl.htm


Gerardo

[emoboy83]

really if your going to use radiosity for gi why not use hdri

[gerardstrada]

The good thing about using TGALH, is that isn´t radiosity, but rather is based on the spinning light trick, what makes it very much quicker than Backdrop Radiosity or even FPrime. :)


Gerardo

[tudor]

Originally posted by emoboy83
really if your going to use radiosity for gi why not use hdri

I don't use HDRI, because it is too much of a problem to create them by yourself, and the ones I have rarely works with the scenes that I use. Just slapping on a HDRI that has nothing in common with your scene looks odd. Just a simpel thing as adjusting the lighting angle becomes a problem. Also there is the problem with many HDRI's giving grainy result even though I add FPblur to them.

[emoboy83]

whoops/ double post

[emoboy83]

really if your going to use radiosity for gi why not use hdri
i say this due to the fact ive only lit models that appear on there own and do not need a accurate re-creation of lighting for a plate etc.

[whitestar]

don't forget that with sky domes you can set it to 'unseen by camera and still get the lighting thats produced by it but not the object

[riki]

Some good points tudor. I know I'd feel better about HDRI if I could create my own.

[gerardstrada]

You can:

http://www.dbki.org/tutorials/eng/compositing/composit.htm



Gerardo

[riki]

What Paint Program can you use to edit them on a Mac?

[gerardstrada]

For Mac the only one that I know is Cinepaint:

http://cinepaint.sourceforge.net/

but is to retouch them, not to create them



Gerardo