population madness

[digitalguru]

Just about to launch into a scene of a forest I'm planning to to render in TG. I have lots of assets to add, PlantFactory trees (great find now it's free) and lots of meshes for ground cover (twigs, leaves, mosses etc). I want enough variation for realism, so I'm thinking 3 or 4 variations of trees, and all other elements. How well does TGD handle many populations? What's the maximum number of populations anybody has had in a scene? (and ram usage?)

I'm looking at Dune's work as I'm writing this, some great renders with a lot of nice variation in the vegetation - wondering how many population you had in scene and how manageable it was?

[Dune]

I'm looking forward to see your work on this. I usually have about 50-20 or so pops of grasses and trees. But they are my own, with not extremely heavy textures or vertex count. Especially for more distant stuff in large coverage, I tend to use lowpoly trees, or the internal grass. Precise location of front, heavy stuff, so nothing is 'wasted' behind the camera.
RAM usage usually under 20 gigs. But I don't know what happens if you plant 'Factory' trees in big pops ...

[digitalguru]

Thanks Dune! 50 or so populations, thought you might have said less, so that's encouraging..

Shot is animated with the camera panning left to right and close to the ground, so layering levels of detail f.g. to b.g will help. I'm starting with 4k textures (esp. for pops with fine detail like moss) so will see how that goes memory wise.

Since the shot is quite close to the ground, having a good variation of plants will be essential, but for extreme close up flora, I'll probably render in Maya and comp it over.

[Dune]

Oops, typo! I meant 10-20 pops
But if the shot is close to ground, you won't need an extensive field of hires veggies, just keep it as much to the front as possible, especially with big numbers of pops. Good luck.

[digitalguru]

Oops, typo! I meant 10-20 pops

LOL - I was just about to go for it...

I'm using image files to texture my terrain (looks good) and my render hits 12gb with out any populations, so will see how that goes. At least I've got 96gb of ram to play with....

[Dune]

96 gigs ... nothing to worry about then, I'd say.

[digitalguru]

Testing population renders a.t.m and this is the first time I've tried a scene where there is a canopy of trees covering the terrain. First thing I've noticed is while there a sufficient density of trees in my test scene to allow light through, I'm not getting much bounce on the ground, my shadows are still quite black. I've tried path tracing and standard renderer with more cache detail with similar results.

ANybody have any good tips for achieving this in TG? I'm trying to get a nice dappled light coming through the tree canopy.

[Dune]

I also had some trouble getting enough light in dark areas under canopies. One thing I always do is reduce opacity of the leaves, which does have an effect, let's more light through. Not under 0.5000001 of course. With standard you can up the surface GI, which won't work with PT of course. An extra no shadow sun at 0.1 or so high up will probably also get more light in the darks. Or increase exposure, but then sky may get too bright. More clouds may reflect more light in too, I'd say.

[digitalguru]

Thanks Dune, some good tips! Just tried them and, as you say, the leaf opacity make the best contribution. Good it works with the standard renderer, but path tracing also benefits.

[digitalguru]

just made some initial tests using your suggestions for lighting (but only one population in this one ) - starting to work well.


 

[Dune]

These look great, very natural. Glad it works ok. Nice bit of eroded hillside, btw.

[digitalguru]

Experimenting in Maya with this. I'll have to do the foreground trees in Maya anyway as I have a vehicle driving through this scene and I need to have the tree shadows casting on to the car. The trick to this as you mentioned, is to reduce the opacity of the leaf shaders ( but keeping it just above 0.5 as anything at that value or below just makes opacity 0) I get why TG is doing this - using opacity masks for leaf cutouts is not too taxing on the renderer (as opposed to using transparency).

Trying this in Maya I get much the same effect, it's the shadows from the leaves that mostly darken the scene. I'm using a ray switch shader to use a shader just for leaf shadow casting which has transparency set to the leaf color.  In initial tests simulates the effect of light diffusing through the trees (still testing though and not sure how much overhead this adds to render times for a forest of trees ).

It's a gnarly problem, and even in Maya/Arnold, there doesn't seem to be a way to do this other than "faking" it (i.e separate shader for the leaf shadow casting). But as this type of scene is quite common in TG, maybe it's something for the future...

[digitalguru]

Here's a test in Maya to illustrate -

Standard shader:


Shader with ray switch for shadows (on leaves):

[Dune]

The opacity shader is an interesting thing anyway. For hair masks for instance, I often set to 2 or 3 to strengthen the sometimes softish or very thin (jpg) masks to see all the hairs. And world opacity is an extremely useful thing too, e.g. to get rid of loose grass (from wider objects) on narrow paths, or too loose leaves of one pop on, say, higher altitudes.

[Stormlord]

Testing population renders a.t.m and this is the first time I've tried a scene where there is a canopy of trees covering the terrain. First thing I've noticed is while there a sufficient density of trees in my test scene to allow light through, I'm not getting much bounce on the ground, my shadows are still quite black. I've tried path tracing and standard renderer with more cache detail with similar results.

ANybody have any good tips for achieving this in TG? I'm trying to get a nice dappled light coming through the tree canopy.

What really helps is to render a separate vegetation pass and adding it with negative multiply in Photoshop.
I did this in some of my renderings, where I ran into the same problem...

This is a good way to go...!!!
Because with the percentage slider you can add very precise how much you will lighten up your vegetation.

 
Pacific Island 2024 by Dirk Kipper

1 pass without vegetation
2 pass normaly rendered (trees are very dark!)
3 pass vegetation against a neutral black background -> Overlay in Photoshop with negative multiply 65%
4 final image with a bright and superb vegetation

That's the way I do it sometimes...
But doing it the way Ulco described is also a very clever solution.

STORMLORD