How to make a proper skydome w/ material properties?

PA_ThePhilosopher

Hey guys, I have heard there is a technique of making a decent skydome for iRay (using sphere primitive maybe?) that allows you to change its material properties as if it were an object in the scene, thus giving you more control. Can anyone clue me in here on how this is done, and how it can be layered in conjunction with the day sun and sky. Thanks again.

Oso3D

There have been several threads on the subject, I suggest doing a search (only because it's been discussed exhaustively).

As a recap, there are several ways to do it:

Use skydome map in the Environment Map. Problem: skydome maps are guaranteed to have bad lighting, and can look a bit blurry doing this (though Finite Dome can help).

Use skydome, take image map into Emission channel. Much of the same problem as previous -- both these situations can be improved by placing a point or spotlight with geometry and lining up with the apparent sun in the skydome.

Use skydome, take image map into Glossy Color, set Refraction to 1/1, and combine with Sky/Sun. Drop Environmental Strength a bit until you can see the sun, then move it to line up with the sun in the skydome.

 

PA_ThePhilosopher

Thanks for the tip Timmins. When you say "use skydome," that's where I'm lost. I don't know what that means.

I did try searching for it but I have been having difficulty finding anything on this new forum layout. Do you happen to know where that thread is that goes into details about this?

Many thanks.

Oso3D

A skydome is usually a sphere or a hemisphere with an image mapped to it. A lot of environment/architecture products, particularly 3DL products that make up most of the store, have them.

In 3DL, it's pretty easy -- you make a big dome, make sure it doesn't cast shadows, put some appropriate backdrop on it, done. But in Iray you can't just magic away shadows. Sooo... trickery!

 

Oso3D

Hmm. Can't find the original threads, but I had another idea for the transparent skydome idea:

Base skydome is a sphere with a spherically projected backdrop. Normal skydome.

Put image in Glossy Color, set glossy weight to 0, Refraction IOR/Weight 1/1. This turns the entire sky into a gobbo, essentially -- when illuminated from outside, it 'glows' through.

Now, previously, I suggested lining up the Sun/sky with the sun in the image. Alternately, putting a spotlight where the sun is.

But another idea occurs to me: put flat white in the Environmental map, creating an even white glow from 'outside.'

Then:

Go into layers, (LIE) and create a cutout opacity where the sun should be (you might want to do this in an image editor, starting with the sky image). Then increase environmental strength until the sun is 'bright enough' and then darken glossy color to dim the rest of the skydome.

Alternately, do the same thing in Glossy with some kind of multiplier, so the sun spot is very light and everything else is dim (I worry this might suffer due to lack of dynamic range in the image, however).

 

One problem I suspect affects many images is that clouds are actually incredibly bright. In a very real sense, our visual system 'flattens' what we see. This poses problems with trying to recreate images.

Once I'm done with this render I'll have to experiment. hmm.

 

Oso3D

Sigh. And experiment after experiment, the images just come out looking muddy and blech.

 

glaseye

timmins.william said:

Sigh. And experiment after experiment, the images just come out looking muddy and blech.

 

Been there, done that, feel your pain..... (But I'll keep trying)

(And it seems some threads have been merged......)

 

glaseye

Just to give an idea what I ran into.

This image uses my own skydome + texture combined with the Iray Sun/Sky settings. Focal lenght is 35mm. If you look careful you can see the sun disk just above the rock on the right side of the image (no sundisk visible on the texture itself. I haven;t tried this yet with a water plane or any other reflective surface, so don't know how well that works.....

 At 1st glance it doesn't look bad. But wait.......

glaseye

A 2nd test image, now with a focal length of 135mm. Some strange regular/irregular fuzzy diagonal patterns are now visible (don't know how else to describe this, my knowledge of the English language does not cover this . It happens with more textures I tried, some even worse visible then this one......  Tried adjusting just about every logical and illogical setting, no change. Tried other domes, same result.... Ouch.... but I stil keep trying.

 

Oso3D

Increasing subd on the dome can help. A little.

glaseye

timmins.william said:

Increasing subd on the dome can help. A little.

Nope, neither increasing nor decreasing SubD did any good, not on my own dome or the other domes/spheres I tried.  Scaling up or down also not. Like I said tried just about anything (and still keep on trying)

But keep the suggestions coming....... who knows......

Oso3D

Be sure to wear fresh shirt and a tall hat!

glaseye

Well, I work with Vue as well, so I've learned to be patient, and calm, and to try again, and again, and again and (add infinite loop here)