[Fixed]”Doubled” shadow on alpha discarded pixels

Troubleshooting graphics
1

I have a plain textured (lighting) quad.



Just above it I have a separate textured (lighting) quad.



The “floating” quad has a partially transparent texture and has alphaTest and falloff set.



Both are set to receive shadows, PSSM shadow renderer is running.





Everything looks and works perfectly, until I move a card (casting shadows) over the floating quad.





Over the areas with no overlap the shadow looks normal, as soon as it crosses over the area though it gets a darker (looks as though it is being applied twice). This definitely happens in the area with the transparent pixels (and there is a very clear line where the shadow crosses the edge of the quad). It’s harder to see on the non-transparent ones but it looks as though the shadow is normal there.



Thanks,

Z

2

Screen shot? :smiley:

3

use AlphaDiscardThresold on the lighting material instead of the alphaFalloff render state

1 Like
4
@t0neg0d said:
Screen shot? :D


I had one ready to go but the image upload site refused to upload it and I didn't have time to go back and upload it to our servers.

@nehon said:
use AlphaDiscardThresold on the lighting material instead of the alphaFalloff render state


http://hub.jmonkeyengine.org/groups/development-discussion-jme3/forum/topic/transparency-and-shadows-possible-breaking-change/

Didn't that say to switch to alphaFaloff instead of alphaDiscard?
5

Ok, I removed the render state stuff and added:

[java]

mat.setBoolean("UseAlpha", true);

mat.setFloat("AlphaDiscardThreshold", 0.5f);

[/java]



It works perfectly now. Thanks :slight_smile:

6

Yep but I had to revert it back.

All is explained here http://hub.jmonkeyengine.org/groups/development-discussion-jme3/forum/topic/shadows-again/?topic_page=1&num=15#post-191211

7

Ahh, ok. Thanks again :slight_smile:

8
@zarch said:
[java]
mat.setBoolean("UseAlpha", true);
[/java]


I'm too tired to go look at the shader. Why does this uniform exist? I don't recall any encapsulation around the discard check. Does it really have anything to do with that? I seem to remember is looking something like:

[java]if (color.a < m_AlphaDiscardThreshold) {
discard;
}[/java]

Probably just not remembering correctly... but I don't remember this being used with AlphaMap... as that's a define. Seeeeew.... what's this for?

EDIT: Betting it's further into the light calculation and decides if to set the alpha after the fact or leave it at the current 1.0