Found the solution for rar files: sudo aptitude install unrar, then unrar x <name of the file>.
Problems with ct3000:
1) I opened the Blender file and first problem hits me: The mesh is totally triangulated.
Why is this? Ideally there should not be ONE triangle in an entire mesh. Less than ideal, but
acceptable, would be if 90% of the polygons were quads, and 10% or less were triangles.
But it seems that every model coming in is 100% triangulated.
2) No edges marked sharp. Instead, the edge split attribute was set to work from angle.
[From Angle] should be off; and edges that should look sharp should be marked so.
Otherwise there's always going to be exceptions to the rule that will look odd because
they were supposed to look smooth but the angle was too large, while others should have
looked sharp, but ended up smooth because the angle was too shallow. Just manually mark
edges sharp that should look sharp. This serves also as "documentation" of your intent, and
avoids the shading's changing when you edit the mesh, or when you turn on subdivision for
the bakes.
3) I decided to fix the problem of triangulation by using Blender's Shift-J command, to join
triangles into quads. It did a pretty good job, actually; but look what I saw when I looked
at the UV layout:
And you know why that happened?
Because when Blender joined triangles, sometimes it joined triangles that were in separate
UV islands. Why? Because Blender has no way to know, with this mesh, because there are
no edges marked as seams. And why are there no seams? Because someone decided to use
an automatic unwrapper.
I've been saying it for months: DON'T use automatic unwrappers. They produce garbage.
Place seams intelligently by highlighting edges and Ctrl-E -> Mark Seam. Once you have
all your islands separated by seams, then U -> Unwrap. Then you move the islands out of
the texture space, and you work hard, for about a week or more, organizing them:
- Grouping them by materials.
- Orienting them so that the forward direction in ship's space points up in the texture.
- And very importantly, leaving space between islands. At least 3 or 4 pixels.
Here all the islands are touching. That produces horrendous artifacts around edges all
over the place. You can't bake an ambient occlusion like that, because a bright and a
dark island touching each other produce artifacts at the seams.
We need to change the modus operandi:
When I work on a model, I post pictures of my progress at least once a day; and I share
the blend file whenever anybody asks. I make sure I get as much feedback as possible
at every step of the way. Otherwise you end up spending god knows how much time
making a texture (50 megabytes worth of layers in this case) that can only end up in
the recycling bin, because the UV layout is un-usable.
And before you point this out... Yes, you CAN tell the automatic unwrapper to leave
space between islands. The problem with automatic unwrappers, though, is that they
don't place seams. They don't mark edges as seams. So you can't work with the mesh
anymore, once you produce such unwraps. The moment you join two polygons, --not
to speak of turning on subdivision, or beveling... you start getting bridges across the
screen joining islands, like above. DON'T use automatic unwrappers. Do it the hard
way, and do it right.