2nd UV Channel [UDK Lightning]

Gazu · Sep 2012

Hi Guys!

First, sorry for my bad english, im from germany.

I had troubles Build that Light correctly in UDK.
It seems to be the 2nd UV Channel...there i do something wrong.

1. Opinion :
I Combine all Meshes of my House into one, and then i have this :
(I made pieces of the house, like the boards on the roof, separately, so i have 5-6 Diffuse Materials, for a clearer UV Mapping)

Have i to organize now all 2nd UVs in 0-1 Space?
But u see, theres no more Space, can i reduce the 2nd UVs ?

2. Opinion:
Every Mesh of the House, becames a own 2nd UV Channel?
UV Texture Editor -> Polygons -> Copy UVs to UV Set -> Copy into new UV Set -> Name iT!

Or are that 2 opinions totaly wrong?

Can somebody help me?

Greetz from germany
Gazu

Shogun3d · Sep 2012

The approach you're taking is fine, it is the result that you have confused.

Essentially you are saving yourself a lot of time as you unwrap/lightmap as you go, approach. Which is great, but you need to remember to set everything to non-overlap distributed uv layout in the 2nd channel when imported into Unreal.

For example, if your object is 1 house. That house needs to have it's own set of unique UVW's in the 2nd channel. Now, UDK can generate these on its own, or generate based off of your 1st uv set (which is great for simple primitive objects) but is better to customize your 2nd set for complex objects.

1. Copy your UV's over to Channel 2.

2. Arrange UVW's in Channel to 0-1 space, NON-overlap. Everything must be arranged with no overlaps otherwise you will receive bad lightmap bakes.

http://wiki.polycount.com/LightMap
http://www.hourences.com/tutorials-ue3-lightmapping/

Gazu · Sep 2012

Here is a Screen, where i didnt know about that 2nd UV Map ^^

Just Alpha Status, not done yet!

U mean, alle the UVs i see in the first Picture, i must organize them in 0-1 space?
But i have to reduce them much all, because the space is full, is that bad?

Thx and greetz

Shogun3d · Sep 2012

Yes, you need to organize them into 0-1 space PER Unreal Object. So if the house is all 1 object, that is placed on its own (ideally) in udk, it needs to retain it own 2nd channel uv set.

Judging by your screenshot. House 1 object, Barrel 1 object, Board 1 object.

Or if you're using a modular approach. Support beam + Awning = 1 object. Roof, 1 object, walls, 1 object. etc etc. Then those objects retain their own lightmap resolution and uv set PER object.

Gazu · Sep 2012

Ok!

So then i go into Object Mode and Select every Mesh individually(The House is made of more then 1 Mesh, its divided in roof, windows, door...)

After Selecting one Part of the House, like the Window, i took his UV Layout, and just Copy it into a new UV Set named for example : LightningWindow.

Thats it? Export as FBX and Import into UDK...?

After i make the 2nd UV Channel for every Mesh, can i Combine the whole House into 1 Mesh?

Thats easyer for Import in UDK. Just have to import 1 FBX and click the Checkmarks for IMPORT MATERIALS.

WarrenM · Sep 2012

After i make the 2nd UV Channel for every Mesh, can i Combine the whole House into 1 Mesh?

You can but then you need to go into the second UV channel for the merged mesh and make sure everything is laid out in it's own unique space, within the 0-1 borders. Lightmaps require that every UV island be unique and not be overlapping any others. Otherwise you'll get weird results.

Gazu · Sep 2012

I cant make a 2nd UV Channel for every mesh separately and then COMBINE all meshes together in Maya.

The saven UV Sets will get broken.

Must arrange all Meshes of the house now per Hand in the UDK, OMG....

EDIT:

Ok, so when i Combine all Meshes together, the UVs of all Meshes will come together on ONE 0-1 Space, right?
So i must arrange them again, with no overlapping aso..

So i can do this in two ways:
1. Arrange the UVs of all Meshes in Maya to export the complete Scene in UDK.

2. Make separately 2nd UV Channels for every single Mesh, but then i have to arrange the whole Mesh in the UDK, because a 1 File Export is not possible, because of the UVs.

Question:
Can the original UV Map and the Lightning UV Copy, overlap ?
Because ive done that now like the 2. Way, but UDK says i have overlapped UVs.....................

Im going crazy....

ZacD · Sep 2012

The light map cannot have ANY overlapped uv's, that includes faces that apear as edges on a UV map. Udk has has an auto unwrap for unique UV's if you open up a static mesh.

WarrenM · Sep 2012

The 2 UV channels have nothing to do with each other. The first can overlap all day and it doesn't matter. They can both use the full 0-1 space.

It's only the lightmap that can't overlap. Looking at your second shot, see the crossbeam piece of wood that runs horizontally in the UV map? It's overlapping the vertical pieces. Stop that.

Gazu · Sep 2012

OK THANK YOU!
THATs why UDK Says i have overlapping UVs .... THANK YOU ^^

crazy, crazy, crazy.... ^^

2nd UV Channel [UDK Lightning]

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