[BUG]Problem blending alpha masked materials **fixed**

[Zom-B]

Hey guys,

today I played with some trees and leaf material in Indigo, and tried to optimize my material setup for such objects.

For optimal rendering speed I need to use a bw mask image to enable step-blend, since that isn't available for alpha PNGs and TIFs
(without step blend you get less samples/sec and more "block-noise")
Any chance to get the step-blend feature for them?!

I created a phong material and a Diffuse Transmitter, to blend them together (using some kind of thickness map).

The Problem here is now that this blended material causes some nasty artifacts in early stages and Fireflies later, as you can see in the example images.
The artifact image has a 50% blend of both materials without the "thickness-map"!
Rendered in PT+BiDir.

Phong only:

The Phong material only!

Diffuse Transmitter only:

The Diffuse Transmitter material only!

Blended material:

the blended material

Artifacts @ 100% zoom:

The blended material after 1 and 20min

BTW: that issue is also happening if I use alpha PNGs as textures

[OnoSendai]

Hi Zom-B,
Can you please send me a simple scene showing this problem?

Btw, when Indigo loads a PNG with an alpha channel, it will make a blend material with step blend enabled, not disabled.

[Zom-B]

Hi Zom-B,
Can you please send me a simple scene showing this problem?

I attached a pigs file.

Btw, when Indigo loads a PNG with an alpha channel, it will make a blend material with step blend enabled, not disabled.

I benchmarked that and had lower samples/sec and more block noise :/
Will rebenchmark tomorrow morning again, for more solid arguments

[OnoSendai]

Hi Zom-B,
This leaf seems to render fine if step blend is enabled.
One thing I noticed though is the way the material hierarchy is set up.

You have the root material as a blend of two blends, each of which is a blend with a null material.

It would be better to set up the root material as a blend of two materials: a null material and a blend of diffuse and diffuse transmitter.

Was this material set up manually, or is it auto-generated from PNGs with alpha?

[OnoSendai]

Ah, now I see what you mean.
it makes no sense to set the root material to step blend on (as it's not a blend with null), and with it off, the null areas are occluding rays incorrectly.
bug found, should be easy to fix, thanks for the report!

having said that, I would still recommend setting up the material the other way that I said.

Cheers,
nick

[Zom-B]

This leaf seems to render fine if step blend is enabled.

But I used some "thickness Map" to blend Phong + Diffuse-Transmitter together, using step blend this gradient thickness will be lost and converted into pixels that are full Phong and pixels that are full DT!

It would be better to set up the root material as a blend of two materials: a null material and a blend of diffuse and diffuse transmitter.

It is done that way to have a final blend using a "Thickness map". To Do so I needed to have the two materials be cut out first, since the last blending is about mixing the leaf together, and not about mixing it with null!

Was this material set up manually, or is it auto-generated from PNGs with alpha?

There is no alpha in this leafs, I used a Mask to cut them out in Indigo (because of the speed issue I still have to proof ^^)


**EDIT**
Ok, now I understood your way of blending, sorry, needed a first coffe to do so -.-'

I blend Phong + DT with my Thickness map, and the cut it out with a mask... so simple ^^

[OnoSendai]

Fixed for next release.

[Zom-B]

Awesome!!!
Thanx a lot!

[Pibuz]

..followed the topic but hardly understood that..

BTW, is the fixed bug something interesting the sketchup users too?

[Zom-B]

Hey Pibuz, this bug happens if you blend two materials together using alpha in a certain way, like here for the leafs of the tree see that image.
After that is fixed you'll notice faster & cleaner rendering (with that before buged kind of blending).

[Pibuz]

I usually use PNG with transparent background for leaves and such things.
Maybe I should wait for Whaat to explain the thing in a technical SU-oriented way to this poor SU user