Black Faces

[Pamela Galli]

The bottom of my pool stays black no matter what. The normals are not flipped, I restarted Blender, I exported and imported as .obj. 

Anyone have a clue about why?

 

 

 

[Alisha Matova]

I would guess that those faces are not assigned to a texture. Try selecting them and opening a new texture or pinning them to an extisting one.

[Nacy Nightfire]

I believe Alisha is correct here.  See post: http://community.secondlife.com/t5/Mesh/I-invert-normals-to-bake-correctly/td-p/1568345. It's not a normal problem it's an unassigned faces problem.

[Drongle McMahon]

But some of the triangles are partly textured. Looks to me like the wrong UV map/texture combination on the bottom of the pool. Is there more than one UV map in the Blender file? Is it using the right texture?

[Pamela Galli]

I forgot to add, the faces have been assigned a material -- I checked several times.

 

And it turns out it is the same problem as before -- If I flip the normals, the texture will bake properly.  But I am betting as with the other, I will need to have the normals facing the correct way to actually import the model correctly. Weird.

[Pamela Galli]

Found it -- I hit Remove Doubles and it took out 32 vertices.  So, double geometry (something Nacy often tells me to check!).

[Alisha Matova]

Yay!

I tend to use remove doubles a lot. Instead of weld. It is pretty handy, as it has a radius adjustment.

Which made me think This:  The brick area of could be lower poly.  Please don't take that the wrong way!  But this is exactly what I use 'remove doubles' for.  I would grab all the verts from one corner of the outer brick edge and scale them to zero (S,0).  Then repeat that on all 4 corners and remove doubles.  Zoom, -32 verts. =D

 

This one has some extra faces and verts along the flat edges.

 

 

 

 

 

 

 

 

This one I removed all the extra poly. It is almost half the faces. I think the center circle could be simpler as well, but the pool connection makes that a bit more complicated to illustrate.

[Pamela Galli]

Thanks Alisha -- yes I just discovered it comes out higher LI than I want, so will give it a try!

[Nacy Nightfire]

Good point about the remove doubles radial adjustment feature.  I use this all the time, and quite frankly I consider it a "better decimator"  in certain circumstances.  Thanks for showing us how you'd use it in this example.

[Masami Kuramoto]

Btw, unassigned faces appear white in textured draw mode, not black.

In 2.49 and earlier they were drawn pink, if I remember correctly.

[Nacy Nightfire]

True Masami, but if you aren't in Texture draw mode to notice this and you bake, these faces will appear black on the bake.

[Chosen Few]

Here's one more thing you may want to add to your general checklist, in case something like this ever happens again.  Areas with overlapping UV's will often bake black.  I'm not sure if that's the case in Blender in particular, but it is the case in many programs.  When you're not baking, UV stacking is hugely useful, of course.  But if you are baking, it's a no-no.

[Drongle McMahon]

In Blender 2.49b and 2.63, they just bake on top of each other. Not sure what determines the stacking order though. This is a cube (all edges seams, bake texture only) ...

 

[Masami Kuramoto]

One of Blender's less prominent features is that bake target images can be assigned on a per-face basis. So even if there are multiple overlapping islands in a UV map layout, it is still possible to bake them properly because a single bake operation can render to multiple target images at once.

[Nacy Nightfire]

However each overlapped "group" of uvs will then need to be seperated by material group or this will be meaningless for the purposes of SL.

[Masami Kuramoto]

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Nacy Nightfire wrote:

However each overlapped "group" of uvs will then need to be seperated by material group

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Yes, but not necessarily at the time of baking. The input materials may be totally different and even use different UV layouts. Baking multiple images with a single click is a huge timesaver, especially when you do full render bakes for SL including shadows and highlights, because it's hard to get the lighting right the first time. Imagine you had to redo up to eight separate bakes every time you move a lamp...

[Nacy Nightfire]

You have a point Masami, but I'd move the lighting and not the mesh.

Also you can temporarily set up an additional "rough and ready" UV set  which has everything on it and direct your test bake to this temporary bake set up as that single image then delete that uv set when you are satisfied with your lighting, etc..  I repeat for anyone new to this techique: Make sure you delete this test UV before uploading or your textures will be misaligned in SL.

My point was that for every overlapped UV you must seperate it by a material group and assign it to a seperate texture so you don't bake the overlapping geometry on top of itself AND have SL set up the texture faces properly.

*edited to replace the word "lamp" with mesh (I was modeling a lamp when I wrote that  and meant to write mesh- whoops!)