These trees are gonna kill me

[riggles]

Not the trees themselves, but their leaf opacity masks.. Using a grayscale image to mask the shape of the leaves quadruples my render time. Is this typical? Eek, I hope not. I'm gonna be using a fair amount of vegetation, and they all use opacity maps to get their leaf shape. Turning off alpha shadows saves a little time, but the self-shadowing on the tree looks blocky and bad. Is there something I'm missing?

[SimonJM]

Sadly, from what I know, no. Transparency/opacity maps tend to hit render time. Layered maps, such as with hair, tend to be particularly bad.

[riggles]

Bummer. The speed gains in GI and DoF with Octane are undone by this one thing.

[LudovicRouy]

I've heard somewhere that converting leafs to real geometry gives a faster rendering but didn't try it....

[SimonJM]

I still get faster throughput with Octane with stuff like Andrey Pestryakov's stuff which (and I don't want to single him out) does have a tendency to be transmap heavy on the foliage, of which there can be a lot than I do with plain Daz Studio and ray-traced shadows.

[Daniel]

It takes a lot of calculations for rays to pass through a whole heap of invisible geometry. It's much better to modify your leaf geometry (which I'm assuming is one quad), cut it a few times and modify the shape to as closely resemble the texture as possible. It will increase the polys of each leaf by 4-5 times, but you should see a performance increase.

[ROUBAL]

Geometry with instances saves a lot of memory and computing power as well compared to textures with alpha.

In this scene, the hedges have real modelled leaves, and the maple trees have planes with apha (I mapped 3 leaves per plane). I will work again on this scene and I plan try to rebuild the trees using geometry instead of alpha for the maple leaves.

This being said, instances are really interesting for medium complexity object. Too simple things like individual leaves require as much memory as non instanced, because the amount of objects coordinates becomes equal to the number of vertices of a more complex object or the number of pixels of a texture. So it is better to use branches as instances, rather than simple leaves.

[LudovicRouy]

Thanks for this trick Roubal,

I didn't try instances but now I'll be aware and would make more huge model for it !

[riggles]

It takes a lot of calculations for rays to pass through a whole heap of invisible geometry. It's much better to modify your leaf geometry (which I'm assuming is one quad), cut it a few times and modify the shape to as closely resemble the texture as possible. It will increase the polys of each leaf by 4-5 times, but you should see a performance increase.

Using geo instead of opacity maps sounds nice but, unless I'm missing something, is not easy to implement. All the trees/plants models from XFrog, Evermotion, Tree Sketch, etc, are all non-instanced flat planes with opacity maps. This is the standard way foliage models are produced and sold. Having to recreate all the leaves manually for each one is a huge time-suck, and doesn't seem like a viable option for me.

I can understand that alpha maps increase render times, but in MODO, I'm used to that being a max 50% increase with trees, not a 400% increase like in Octane.

[ROUBAL]

I agree that it is not obvious with trees bought in packages. I mainly make my own trees. You can start on the basis of trunc and branches of your existing models, and add sub-branches with modelled leaves as instances...