Rendering cloud animation without terrain and objects, but with their influence+

[TheBadger]

Hello,

I know this has been discussed so a link as an answer will be fine.
I am ready to sit down and finish something I have been playing with for a while. But I need to understand a few things.

I have a Terragen scene rendered. I want to re render the scene as a still but with out the clouds, and render the clouds as animation separately. There is some effect from the terrain and objects on the clouds in the form of volumetric shadows and such (its more like fog or mist, but made from cloud nodes)

I want to render the two parts and composite them together, so the clouds animation and the still scene the clouds are from. I want to do it this way to save time on the clouds animation rendering, as well as gain much more control over the look by compositing.

1) I can do this?
2) I will get the shadows in the clouds/mist being cast by the objects and/or terrain, but I don't have to render out the  terrain and objects?
3) there is a tutorial on doing passes in the tut section of this forum. Is that all I need to know for this?

ALSO
In the end what IM trying to make is an animated Matte Painting for the environment of some characters acting in the foreground. I will also need to out a spherical environment map to use on the characters in Maya (I will composite the characters over the matte painting).
But I am aware of some issues with the spherical environment map T3 outputs. However I don't see anything from those threads that looks like it will be a big problem.
I just want to make sure that if I get a Terragen spherical map to use to get the lighting and refections and such on my characters right, that its not really going to be a problem. Good to go?!

Not a terrible hurry on this, I have a lot to do and set up yet. And I need to buy and transfer my T2 stuff to T3 yet. But to be sure of everything before would be nice feeling.

[Oshyan]

Is the entire point of this simply to save time on rendering the atmosphere? How exactly are you expecting to save time on that part by rendering it separately?

- Oshyan

[Matt]

It sounds like you might need the terrain to "hold out" the clouds in your cloud render. If so, turning off "Surfaces visible" on the render node should do what I think you want to do, and give you a render with just the clouds and atmosphere. Shadows and GI from terrain will still affect the clouds. The terrain displacement will be rendered (it needs to be to hold out the clouds) but it will be rendered black.

Bear in mind that if you just render a still for the terrain, it won't have any dynamic lighting from the moving clouds. If you can afford the render time, I would render the whole animation with terrain and clouds and use Render Elements to get the compositing control you want.

Matt

[TheBadger]

This is a crop that has some of the lighting effect I want to preserve.
[attach=1]

Oshyan

Is the entire point of this simply to save time on rendering the atmosphere? How exactly are you expecting to save time on that part by rendering it separately?

Well mostly. I thought I would save time per frame (substantial?) simply because there would be much less per frame to render. Not a good way to think about it?!

Matt

Bear in mind that if you just render a still for the terrain, it won't have any dynamic lighting from the moving clouds.

What I was thinking is that the terrain is so overcast and I think pretty evenly lit (more or less) that I could get away with it.

If in seeing the image and hearing my reasoning (wishful thinking ) you still think "If you can afford the render time, I would render the whole animation with terrain and clouds and use Render Elements to get the compositing control you want."
Is the best way, than thats what I'll do. I would rather have one long render time than 2 because what I wanted to do wount look good.

Thanks

[Oshyan]

So were you planning to render 1: a moving cloudscape (i.e. an animated atmosphere), outputting an image sequence, and then 2: a *static* terrain, outputting a *single* image, then composite them together? If so, and your animation truly has little or no effect no the terrain, then yeah you'd save render time if you did what Matt suggests (otherwise it will actually render *more* sky, if you just turned off terrain). However, if you need to render sequences of both terrain and atmosphere, then you save no time rendering them separately (probably the opposite). I would guess the latter is not what you want to do, but it is what I had first understood was your intention...

- Oshyan

[TheBadger]

Ill tell you I wish I had my own render farm, Oshyan. Then I would not be so worried about finding short cuts or gaming the system, so to speak.
I think its at least clear to me the best way is the long way.

But when I get T3 running, one of the first things Ill do is render an old scene to see if I get a faster render. Maybe that alone will solve some of my concerns.
Also, once I have all these individual pieces finally, then I can really see how everything fits together, and at last know for sure what the best way to do things. But regardless, at least there are options!

[Oshyan]

It's sensible to try to find shortcuts, even those with a render farm at their disposal try to minimize render times. When you understand the fundamental workings of the system and what *general* approaches can ease render time, then you can work creatively with a given scene to tune things to your available resources (or confidently determine that it may not be feasible with those current resources). Your original idea may not be a bad one, depending on your end goal and the particulars of your scene, but I suspect you'll spend enough time researching, experimenting, and then compositing separately rendered results later, that you might lose any benefit you would otherwise get.

- Oshyan