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Opacity extremely slow

Posted: Mon Mar 18, 2013 11:13 pm
by v_p_vlasenko
May be I'm doing something wrong but opacity work extremely slow.

Interior shot, outside couple of plants, one of them (pine like) makes render around 7 times slower, while it covers less than 5 percent of image. Rest of plants with bigger leaves don't have such impact on performance. CPU load jumping during rendering from 10-90%
The plant is a bunch of planes opacity with texture.

If I disable opacity or replace it with another texture (big leaf) speed is much higher and CPU load 100%.

Is there anything I can do with that?

Re: Opacity extremely slow

Posted: Tue Mar 19, 2013 8:06 am
by eric nixon
I suspect the engine is at fault here, (there may be an issue with having many pieces of 'opacity' right next to each other, because the ray has to pass through several at once) I'm not sure about this, but I noticed a slowdown when i began to use alpha opacity on grass blades - the greater the area of the grass blade made invisible, the greater the slowdown.

So in summary, I suspect there is no user error here, and your best bet is to use a different tree :) , or wait for the next version of Maxwell.

Re: Opacity extremely slow

Posted: Tue Mar 19, 2013 1:22 pm
by polynurb
Use clipmap instead?!

Re: Opacity extremely slow

Posted: Tue Mar 19, 2013 1:45 pm
by Sebastien Bernard
+1 here or just do it in photoshop when it really drops the performance of your machine down.

Re: Opacity extremely slow

Posted: Tue Mar 19, 2013 2:47 pm
by hatts
Just wondering: for opacity, do you mean making the leaves slightly translucent, or do you mean clipping the shape of the leaf with a clip mask?

Re: Opacity extremely slow

Posted: Tue Mar 19, 2013 4:02 pm
by v_p_vlasenko
Thanks for reply guys.

I mean clip map i guess, "Opacity/mask" in Layer properties. The main impact going from clip map, even without translucency and any textures it extremely slow. Seems like the situation like Eric wrote - "the greater the area of the grass blade made invisible, the greater the slowdown." So if i use alpha map with just a bit of transparency (like big leaf) - everything fine, but in case of that plant - it's not possible.

Re: Opacity extremely slow

Posted: Tue Mar 19, 2013 4:29 pm
by hatts
Interesting, I've been using clip-mapped leaves for a while now on a particularly large model and it's making me wonder if it's slowing me down. Going to double-check that now.

Re: Opacity extremely slow

Posted: Sun Mar 24, 2013 8:38 pm
by eric nixon
I forgot to mention its only an issue when the leaf geo is intersecting, which on most models it will be (and mw grass self intersects too)