Moon glow revisited

[N-drju]

Hello everyone,

So far, I was never able to wrap my head around one thing. Namely, how can you create a moon (planet object) and add a nice, nightly glow to it using another sunlight?

The problem begins with the fact that you cannot use the planet object, because it will cast shadow on the surface much like during eclipse. Also, there is no option to turn shadows off in planet objects.

Thus, I switched to standard sphere, turned off the shadow, gave it a cosmic size, pulled it into orbit and also checked the "receive shadows from surfaces" in the atmo tab. This time, the glow and light were visible, but... The light shines right through the sphere.

This is a very strange behavior - when you place the sphere right next to the camera the light source will be, more or less, obscured as it should be while the atmo glow is visible. See the following picture:

[attach=1]

Now, see what happens when the exact same sphere is increased in size and thrust into orbit:

[attach=2]

What the hey is always wrong with those things?

[Dune]

I think (not sure) I did that once by using a planet with an atmo for the glow, extending the atmo real wide, and using a that-planet-centered camera and Z-depth distance shader, pointing away to get rid of the haze in front of the planet. Worth a try maybe...
The trouble with placing a planet/sphere that far is that it's hard to control anothere sphere right behind it (which I've done as well, I think), and you have to take care it doesn't fall outside the outer background sphere.

[N-drju]

Hm, but that still leaves me with the shadow of that planet. Right?

[Oshyan]

I'm not totally sure how your scene is setup, but I would guess the glow you're seeing is from the atmosphere. If it's a regular non-displaceable sphere it should not need "receive shadows from surfaces", I think, but it's worth tying anyway to see if it fixes this issue (that would be in the Atmosphere Quality tab).

- Oshyan

[N-drju]

Nope. It doesn't work with or without "receive shadows from surfaces" option. Still got that stupid flare in the middle of the "moon".

Also, there is nothing peculiar in this scene. Just a blank project file with a sphere in the sky.

[Oshyan]

I guess I missed where you said above that you turned off shadow casting for the sphere object. So... of course is it not going to occlude the light source... right?

- Oshyan

[N-drju]

Ummm yes, so? How does it help me? Then tell me how to make the planet solid and get rid of its shadow that completely eliminates the glow and light! The planet then is creating an eclipse darkness as in that "Pitch Black" film... Any idea how to do this?

There should be an option to retain the solidity of the object while eliminating its shadow. Equalizing shadow cast by an object with its transparency is a very simplistic view for applications like that, when you try to imitate light cast by celestial bodies.

[Dune]

Displacable (internal) sphere, or no-displacable (alien) sphere... there might be  difference there. Try importing a (non-displacable) sphere from outside.....

[N-drju]

I tried to import a sphere primitive from DAZ Studio and ended up with exact same problems. I call bogus on this one! Terragen cannot create a realistic moon effects at all!

[Kadri]

Nothing is in that aspect realistic in a computer. Some effects are easy, for some you have to use a workaround.
There are many threads here in the forum but have a look at this for example:
http://www.planetside.co.uk/forums/index.php/topic,5156.msg53354.html#msg53354
There some files too there further below. Some files are absent but you can find others on the net instead.

http://www.planetside.co.uk/forums/index.php/topic,15027.0.html another one

[N-drju]

Wow, Kadri... it seems like finally there is some kind of progress! Thank you so much for digging that up from the forums!

The first link does not do any good for me (no atmo glow associated with moonlight) but the second link with Martin's solution is actually starting to work! Man, is he a genius! There are some variables that I do not understand though. I need to tweak the settings more. With a bit of luck I might finally crack it.

[attach=1]

I just need to find a way of lighting up the main terrain now. The light angle that you can see in the picture is waaaay out of alignment, though it is not evident. I still cannot use the sunlight from behind the moon, because of the "eclipse syndrome".

[Kadri]

Haven't tried it myself, have you tried to add another light that is slightly away from the moon
and doesn't have glow and Visible disc enabled?
The slightly different angle would be hard to spot probably.

[Kadri]

Or just comp all of it. Actually that would be easier for all you try here except if you want it all to do in Terragen.

[N-drju]

Um... what does it mean to "...comp all of it"?

If you mean "compile", i.e. pasting an image of the moon in the final render I don't want to do this. I would rather have all of it made in Terragen. For instance, if something should get in the way of the moon disc (leaves, human figure for instance) that would require some postwork... Though I can think of a pretty simple way to do that, especially with the use of clever and easy alpha channels that I have in DAZ Studio for instance.

[Kadri]

"Um... what does it mean to "...comp all of it"?"

Compositing in postwork.
But yeah it looked like you want it in Terragen directly already.