Particle Popping

Imatk

So I have this fire particle that is burning over a tree static mesh.

Everything looks fine, BUT every once in a while the particles will "pop" off and disappear behind the object then "pop" back in front of the object so you can see them again.

I suspect this is Z fighting, but I'm wondering if there's a way to fix this.

Thanks for any help.

sprunghunt

try adjusting the sort mode:

http://udn.epicgames.com/Three/ParticleSystemReference.html#Required Module

Imatk

Yeah that doesn't seem to have any effect. I'm thinking because the sort mode probably only pertains to particles sorting with other particle and not static meshes.

But I'm not sure.

imbueFX

Z fighting would be my first guess. Can you post a video or package?

Imatk

Here's a vid of it:

http://www.samjam.com/3D/TreeFire.mov

imbueFX

Wow, that is crazy bad. If you rotate around the tree, does it the popping suddenly get faster?

Let me ask you this: Are you using depthBiasedAlpha in you material?

My gut tells me this isn't a Z fighting issue. Could be a material sorting issue, maybe? I haven't seen anything pop that bad in my experience with UDK. I'd be interested in playing around with it myself if you can't figure it out.

Imatk

Well the actual tree bark material is translucent which, I believe is why it's doing that.

I needed to set it to translucent so that it "fades" into the scene as I'm taking a clean tree to a burned tree and the only material that will fade is translucent. I tried it with soft masked, but it's more abrupt, although I COULD use that if necessary.

I do have a depth biased alpha on the fire material as well.

imbueFX

So if you set the material to opaque, the particles stop popping?

I'd suggest then you LERP an opaque material instead of fading a translucent material.

Also as a test, get rid of your DBA expression. In our (much older) UDK at work, DBAs in materials cause similar issues all of the time. May not be the issue, but it's worth a shot.

Imatk

Ahhh I never thought of fading it with a LERP thanks man I'll give that a shot.

Yeah it doesn't seem to be happening on an opaque material so maybe that will work.

Thanks

Imatk

Hey just wanted to let you know the Lerp worked out beautifully and it is working perfectly now.

Thanks for the help again man!

imbueFX

*high five*