Foliage best practice

[pingus]

Hello !

I was wondering what are the best practices for Foliages with Vray : mesh VS opacity for leaves.

We used to work with mesh for leaves because we had problems with some render Elements and/or some shaders override (Occlusion, ZDepth filtered and unfiltered, custom shader override...) and it was (in the good old times) longer to render with opacity than polys.
Is it still the case ? or opacity leaves is now the best for rendering leaves & trees.

We aim huge vegetation (quantity and quality) for animation.

Thanks !




Ressources :
- https://www.chaosgroup.com/blog/port...ay-for-3ds-max
- http://www.peterguthrie.net/blog/200...utorial-leaves

[piotrus3333]

to get quality you need opacity for leaves.

[glorybound]

Computers have gotten so much better I haven't worried about this in years. Now, if you have a machine that is older and not beefy enough, opacity might be your enemy.

[pingus]

I'm talking about animation for cinema, so that multiples vegetation (vrayProxy used in Forest) in multiples sets, foreground or background.
Optimisation is so important when you deal with huge quantity of frames & multiples renderFarms.

By the way, in my early tests, it seems that opacity is a bit lighter in RAM but seems to be longer in renderTimes. Is that supposed to be exact ?
I'm continuing investigation.

[DanSHP]

to get quality you need opacity for leaves.

Sorry to jump in on the thread, glad I came across as I am working on updating our foliage library. How are you guys creating your foliage materials? Say, for grass?

Just wondering if my approach is correct???



This is scattered via FP with forest colour map in the diffuse to add variation. Excuse the out of scale daises.

[piotrus3333]

you don’t need material for the back faces if it is the same material as front.
and turn off translucency inside grass01. it only works if mesh has volume. you are getting translucency you need with 2 sided mtl.

[DanSHP]

you don’t need material for the back faces if it is the same material as front.
and turn off translucency inside grass01. it only works if mesh has volume. you are getting translucency you need with 2 sided mtl.

Excellent!

[werticus]

opacity mode makes a big difference.
under the material options:

Opacity mode – Controls how the opacity map works. For more information, see the Opacity mode parameter example below.

Normal – The opacity map is evaluated as normal: the surface lighting is computed and the ray is continued for the transparent effect. The opacity texture is filtered as normal.
Clip – The surface is shaded as either fully opaque or fully transparent depending on the value of the opacity map (i.e. without any randomness). This mode also disables the filtering of the opacity texture. This is the fastest mode, but it might increase flickering when rendering animations.
Stochastic – The surface is randomly shaded as either fully opaque or fully transparent so that on average it appears to be with the correct transparency. This mode reduces lighting calculations but might introduce some noise in areas where the opacity map has gray-scale values. The opacity texture is still filtered as normal.

[pingus]

Hello
We've made new tests and it turn out that planes leaves are munch more expensives in renderTimes than mesh leaves, while a huge polycount difference.

Here our test :
2 leaves : 6 poly for planes & 480 for leave (just added a quadrify to artificially increase the polycount)




2 Trees made with GrowFX & converted into VrayProxy. I've a little difference in scale but it shouldn't interact.

Tree with planes : 460 k polys
Render Time : 5min30
RAM : 3,6 Go


Tree with meshs : 14 Millions poly ( +30%)
Render Time : 3min20
RAM : 7 Go



Forest with 5700 items, 1 vraySun

With planes : ~2.600 M polys
Render Time : ~70 min
RAM : 4 Go


With meshs : ~81.600 M polys
Render Time : ~14 min
RAM : 5 Go


14 minutes only VS 70 min for opacity leaves ! While we have 30x more poly in the mesh scene....

I am doing something wrong or is it as intended ?
I'm continuing tests on shaders for the opacity, to see if i can optimize whatever.

-p-

[Vizioen]

Great that you're actually taking the time to test this, I always wondered the same. To have the best comparison as possible shouldn't the leaves have roughly the same size?

[pingus]

Hey,

I've down my renderTime for a forest with plane from 70min to 28min by lowering blur from 1 to 0,001 in the opacity map.
I'll try to see if this doesn't make the render too noisy.

BUT, this is still a 28min vs 14min for meshs.... 2 time longer for opacity map !.... i'm really wondering if it's worth.

[M.Max]

This is interesting, thanks for sharing.
Could you try "clip" mode for opacity to compare render time?

[fixeighted]

Isn't this going to be scene/output dependent? Also dependent on what is close to the camera.
It seems hard to have a solution which works in all situations unless modelling fidelity and polygon count is not an issue.
As an example - a curved leaf with a complex spiky edge. This simply wouldn't look great if it was a plane with opacity unless it was far away, so it needs at least a curved plane with opacity. Arguably it's better to have quite simplified geometry to avoid the time hit from opacity and potential issues in an animated situation.
From this to the other extreme, which is a fully modelled leaf. And then something inbetween - a partially modelled leaf to describe the curvature well enough, with an opacity to further define the edge detail.
So it's 'horses for courses', no?