Vray and Transparency trees [xfrog - speed tree]

[indigooo]

Why is vray so slow when there are trees with opacity maps leafs? It needs a lot of time to render them, and i dont understand why, if many of the others renderers have less problems with them, any suggestion to decrease the render times when using that kind of trees?

[Dynedain]

try turning off the filtering for the bitmaps - that speeds it up significantly

And speedtree changes your shadowtypes to their own special type that is optimized for opactiy maps - which works fast in scanline, but causes problems in Vray.

Usually just reworking how the opacity maps are setup (monochrome, no filtering, etc) makes things go much much faster in Vray.

[RErender]

Turning off GI generate can speed it up quite a bit too.

[indigooo]

i see. turning off filtering in the texture i gain only a few seconds.. not enough :_(

[Dynedain]

Did you check to make sure that the material only has the RGB channels in the diffuse slot, and only the Alpha as grey in the opacity slot?

That should save you a bit more time

[Giovanni]

I noticed this as well, using a simple scene with Treeshop (the free plugin for billboard trees...).

The scene has one standard light, no GI nor any other special effect, nor shadows.

Just a bunch of billboard trees.

The default scanline renders a 640x480 snapshot in a second (literally).
Switching to Vray (1.46 makes the same scene render in 8 seconds.

Now, 8 to 1 is quite of an increase.

I read the comment from Vlad about transparency maps and how vray needs to stop and recalculate the rays per every transparent point on the geometry, but still...

How comes the scan render is soo fast? Can vray use some simpler (phong?) transparency rendering technique, maybe on demand?

Other question: is there a clip channel in Max materials, somewhere? Maybe clipping maps are faster than transparency maps....



thank you

regards,

gio

[RErender]

No clip channel in the materials (yet ) but you can achieve the same with 2d displacement. I have set up a few trees this way and they do render faster.

[jonasa]

The problems i have faced using Xfrog trees is not as much speed as the problem with alpha channel separation.

1. When i use a VrayMat with refraction map for the leaves i get this result: (even though IOR is 1.001 and affect shadows/alpha is ON)


2. When i use a Max standard material for the leaves i get this result:


Essentially I want to have the quality and speed of the 1. example, but the alpha channel of the 2.

The lower image takes twice as long to render as the top one, and this is for animation, so it does matter

Any ideas?

version: Max6 and Vray 1.46.08

[jonasa]

Got it sorted... using the new opacity map slot... works a treat!

[dbuchhofer]

Noticed this also the other day.. If you are using the Opacity map slot in the vraymtl, don't check the 'affect alpha' button in refraction, or you end up with some very strange results for the alpha channel.

[fgcity]

There was a post on the forum about this issue, the way that i use and that was written was to use the "Blend" material from Max materials, use the mask slot with the Opacity map from the oryginal Mat, Delete the texture from the Opacity slot, and use as reflection on the blend second slot the Vray mat. That way you get the transparency of Vray and the mask from the leaves. I use this technique to work with SpeedTrees. It works quite nice.