Weird shadow seam beetwen mesh ?

Nathan Nguyen

hi everyone !

I have a problem with shadow in UDK

in the image below is a simple wall that I modeled, I Unwrap the second UV channel for lightmap ( the UV is snap to the grid and have enough padding )
every thing work just fine



but when shadow casting between 2 wall, it's start showing the seam :poly127:




and here is my UV unwrap for Lightmap



DO you guy have any tip and trick to do with the lightmap UV, because Unwraping UV for entire environment with everything is snap to the grid and each shell have constant padding is just a real pain in the butt...
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robert.briscoe

Move your UVS away from the edges of the UV space!

r4ptur3

looks like your lightmap might be too lowres which means there is not enough pixel space to describe what's going on. another probably cause is the pixel density between the door and the wall is different. try a 32x32 or 64x64 lightmap. if that doesn't work try to unify the pixel density between the door and wall. also keep in mind the larger the lightmap the less space you need between your shells.

BNielsen

It's a mix of both of the problems above: UV's touching opposite sides = touching.
And it has the curves because of how it's drawn the lightmap, curves up on the right where it touches a dark part of your wall, and down on the left because it's light on the touching UV., For a wall this size,

I would budget about 64X64 for this wall, and tweak the small UV pieces to the left a little bit, off the edge.

Nathan Nguyen

My wall was 256x256 UUnit, so by default UDK set Lightmap for it is 64x64

I tried higher res > didn't work


they said that was waste

http://udn.epicgames.com/Three/LightMapUnwrapping.html#Contiguous UVs and Padding

"Padding around the edges of the lightmap UV layout, however, is not necessary as Lightmass automatically pads around the edges by enough to prevent bleeding artifcats."



I tried to stay away from the UV border but it didn't work

ex : a simple plane, duplicate a few time

here is before I built the light



and here is after



UV

Xendance

Uh, it just looks like you have to use a higher resolution lightmap. Could you show those meshes with the lightmap texel viewmode on?

Nathan Nguyen

sorry, the plane above, I forgot to change the UV channel
the main problem now is the seam still appearing

mAlkAv!An

You won't get to look this right with low res lightmaps just because of the way how distance field shadows work.
Instead of placing multiple flat planes next to each other without a trim in between, merge them to a single larger mesh. If it's one mesh already, stitch the UVs.

Nathan Nguyen

OK, I got it !

I planned to make a modular environment using some static mesh and one master material

seem like I need another plan to cover the seam

thanks you all for helping me

Subtle 1rony

Yes, Ive been there with this problem before. Anytime you have a flat plane meeting up directly with another flat plane you're almost always going to get a seam like that, no matter how perfect your lightmaps are.(I think it is possible to make it seamless if your lightmap pixels line up perfectly, but I found it more trouble than it was worth)

As suggested, hide it with a trim of some sort. After a while, you get used to building with this in mind. Good Luck!