Unreal - Transparent object blocking others

Tulkamir · Nov 2006

Hey, I don't know if this is the best place to ask, but does anyone here know how to fix it in unreal (2) is having a problem where an object with a alpha transparency is blocking other static meshes behind it from being rendered?

I think it's an problem with render priority or sorting, but I'll be damned if I can figure out how to fix it.

If anyone could help that'd be great.

Thanks.

Vailias · Nov 2006

If its not already set try making the material the object uses a final blend with its blend mode set to FB_Alphablend.

Its likely defaulting to overwrite, and might be the cause of blocking the objects behind it.

Tulkamir · Nov 2006

Hey, thanks for the suggestion. I gave it a try and it didn't seem to do it.

Any other ideas?

spitty · Nov 2006

is alphatest checked in your final blend?

or you might need to use masked alpha instead of alpha blending.

you might check out udn, my memory is fading on unreal2 stuff
http://udn.epicgames.com/Main/WebHome

Vailias · Nov 2006

and or, would it be possible to send the offending texture package to me so I can actually test it in ued? It would be much more effective than blind speculation.

vailias at gmail dot com if you choose to send it.

Toomas · Nov 2006

Well it is optimization thingy i think, the engine will not render polys that are fully behind other objects.

Tulkamir · Nov 2006

Thanks for all the help guys.

I just got it working. I had to turn off ZWrite in final blend.

Works perfectly now.

Thanks again.

Penzer · Dec 2006

I got a similiar ut ed problem right now. I've imported a table, the top of it will be glass so it has an alpha channel. UT is optimizing out tris on the bottom half, which flicker from being drawn to not being drawn depending on your viewing angle.

I haven't set up any antiportals yet, so it's not that. My understanding was that UT only works on a per triangle basis with BSP geometry, and should be optimizing on a per-mesh basis for static meshes. I couldn't find anything that helped in the static mesh browser options, or in the properties for this instance of the static mesh. Any ideas would be helpful, and don't mind the placeholder textures :P

Vailias · Dec 2006

penzer. The lod process for imported meshes works by smoothing group borders, and or uv seams, so you'll get culling at the breaks in the uv map first. ALSO if you have unwelded verts it will often lead to holes at the polygon with the separate verts. ITs logically the same as a uv seam to the LOD system.
The only other thing that leads to this sort of look is if you have imported a non triangulated mesh, but the results from that are usually much worse.

Double check the vert issues first, and if they are fine, consider splitting your mesh into 2 parts, one for the top glass and one for the base, and see if the problem sorts itself out.

Penzer · Dec 2006

Mesh is triangulated, verts are welded. I'm at school now, so I'll double check the smoothing groups when I get home. I'll post if it worked or not later tonight, thanks

Penzer · Dec 2006

Back at home now, tried re-importing it again. Double checked the smoothing groups, didn't fix it. I'll run it by a friend tomorrow, see if theres an option I can turn on or anything to fix it. If not, I'll split it into pieces. Thank you

Tulkamir · Dec 2006

Did you read how I solved mine and try it?

Also, are the faces there before you add the material? I'm assuming so. If they are then making the material a Final Blend and turning zWrite to false should fix it right up.

If you need help with any of it just ask at school.

Penzer · Dec 2006

Ya I tried that when I read what worke for you, but it didn't work for me. The problem you were having was that it was optimizing out other meshes being blocked by it. Mine, as far as I can tell, is that tris within the model are being optimized out. That doesn't make any sense, because Unreal is supposed to optimize static meshes on a per-mesh basis and only bsp's on a per triangle basis.

I talked to Mark, he said it might be problems with Alpha sorting. Looking into that now

Delaney King · Dec 2006

I like the unreal 3 solution... rip lit transparencies out of the engine entirely

-yeah yeah, I know.

Unreal - Transparent object blocking others

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