Atmosphere - Receive shadows from surface

[KlausK]

Hi everyone.

While trying some stuff based on this thread "Image map shader over terrain: can it glow? And if so, how?" I came across this setting (see topic) again.
And again - rather frustrated. Attached are two images with only this one setting on or off (sun visible / hidden).
The render times shoot through the roof when turned on (sun hidden).
How does this work? Why does the sun shine through the mountains at all when the sunlight is casting shadows?
Most important question: how does everybody else deal with such a situation?
(solutions which include moving the sun out of the way do NOT apply  )

Any help tips or proven workflow greatly appreciated!

cheers, Klaus

ps: time to render sun - visible: about 4 min - - - - - -time to render sun - hidden: about 58 min

[ajcgi]

Are you raytracing shadows? ie is that turned on in the Extra tab of the renderer?

[Dune]

That's a very strange difference anyway, by just unchecking sun's visibility. Or did you mean 'shadows from terrain'? I guess the latter. There was some solution a while ago, but I forgot where and how, and if that really worked. Moving an invisible object (card/cube, don't know what) between sun and camera, or something. You'd have to do some hard searching.....

[KlausK]

Thanks for answering.

Dune: Yes, the setting under the Quality tab of the Atmosphere: Receive shadows from surfaces
That is what it is named in tg4 beta 2
What you turn on to hide the sun behind a mountain for example. ("May be slow to calculate" - I noticed, hehe)
I am gonna try that invisible blocker. I was thinking along these lines.

ajcgi: yes. I did not change that setting

Attached 2 screenshots of the tabs I am talking about. Settings for - Sun-visible.
btw: the sun`s elevation is set to -1. Maybe that is why it looks a little bit strange to you, Ulco
cheers, Klaus

edit: I attached another image: here I set the Sunlight - Visible disc - Angular diameter fairly high.
One might get away with this trick in certain circumstances.
At least it comes close to the 58 min render where the sun is hidden behind the mountains, I think.
Could not get any blocking geometry to work yet.

[KlausK]

...and then there is always Render Layers, I guess.
Rendering the atmosphere / sunlight and the mountain range seperately and composite.

cheers, KlausK

[bobbystahr]

Didn't this work in the past just fine...I've been running into this as well

[KlausK]

bobbystahr, do you mean the blocking disc / plane / geo?
Could be user error on my side. I don`t know. Never tried it before.

But...I could not resist and rendered the scene with "Receive shadows..." turned on in TG 3.x.
And the render time was 1h 29 min! Picture looks exactely the same to me.
Well, not only scenes with more imported objects benefit from the improved render engine.
30 minutes less than in TG4 Beta2. That`s quite a lote for such a simple setup, don`t you think?

cheers, Klaus

[bobbystahr]

bobbystahr, do you mean the blocking disc / plane / geo?
Could be user error on my side. I don`t know. Never tried it before.

But...I could not resist and rendered the scene with "Receive shadows..." turned on in TG 3.x.
And the render time was 1h 29 min! Picture looks exactely the same to me.
Well, not only scenes with more imported objects benefit from the improved render engine.
30 minutes less than in TG4 Beta2. That`s quite a lote for such a simple setup, don`t you think?

cheers, Klaus

I was referring to the Atmosphere switch as on occasion even having that on in the BETA still allowed the sun to show through; but a bunch of tests today has it working as advertised....weird...must have been something I missed in the error renders.

[Oshyan]

The reason this takes so long (with Receive Shadows enabled) is that the ray tracing of the atmosphere has to reference the *Displacement* of the Terrain, and rendering displacement with raytracing in the current rendering engine is very slow. This is similar to why displacement doesn't work on imported objects with the ray tracer. It's an issue we plan to address in the future but it requires some fairly significant renderer changes unfortunately.

- Oshyan

[bobbystahr]

The reason this takes so long (with Receive Shadows enabled) is that the ray tracing of the atmosphere has to reference the *Displacement* of the Terrain, and rendering displacement with raytracing in the current rendering engine is very slow. This is similar to why displacement doesn't work on imported objects with the ray tracer. It's an issue we plan to address in the future but it requires some fairly significant renderer changes unfortunately.

- Oshyan

well that answers my next question...thanks...