[Ambient Occlusion not cast by object]

Some things you might try:

Select the mesh that isn't contributing to the ao and:

Check normals to be sure they aren't facing the wrong direction

CTL A -  apply location, rotation, scale

If the "offender" has parts that are mirrored ,copied or arrayed apply the modifier .

Shift CTL A and "make duplicates real" in the event  the duplication is a linked duplicate.

 

Note I haven't tested any of these, but they are easy enough to try and one of these might do the trick.

[Blender, problem when using the Transfer UV Maps tool]

I would also like to mention that while I absolutely  agree it is ideal to make the UV's prior to mirroring or creating an array,  I can imagine situations where one might make the UVs before copying, but yet later find that the original UVs are not optimum and one might then choose to rework them at some later point.  So  if the scene is complex and there are many and the parts are repositioned after mirroring the only reasonable option would be to copy the UVS.

[Blender, problem when using the Transfer UV Maps tool]

Very nice plane! Pam Galli kindly directed me to this thread.

I have only a moment here to glance at the issue and need tonight to to absorb this thread where I'll respond tonight in more detail, but off the top of my head when you use the UV transfer on an item created by the mirror modifier you are not actually transfering from one identical item to the other. It's mirrored.  So the result is unconnected UV faces.  It took me ages for figure out why I sometimes had this issue and otherwise not.  For example if you make copies via the array modifier you shouldn't run into this problem.

I recall I figured out a quick fix for this so you can correctly transfer the uvs to mirrored objects.  The procedure is something like mirroring the mirrored part,   THEN copy the UV and then flip it back and reset the normals...something like that, but I have to dig out my notes as I haven't been actively creating mesh this summer.

************** A few hours later***********

Yayy!  I found the video I made to remind myself about this issue.

Here's an example I just whipped up.  I made a quick coffee cup and mirrored it on the x and again on the y.  I then selected each copy and made them seperate objects (in this case the easiest way is to select each and press P>separate by parts which will seperate everything selected into it's own object in one go and since each copy s a single mesh it's a quick way to do this.)

Then I UVd the "master" and then selected each copied object with the master selected last. I pressed Ctrl L and transferred UVs.  Note that the best way to then visualize the problem with copying UVs on mirrored objects is to create an AO texture from the "master" and then assign this texture to all the mirror copied meshes:

 

The "Master copy" is on the left in the back.  Note that the copy on the x axis and on y axis do not look right.  This demonstrates that that although the UV's appear to be correct, the faces are disconnnected and screwed up.  What is interesting is that the copy diagonally opposed to the "Master" copied correctly.  That's because it's a copy of a copy  - mirrored twice - so it's straightened out.

The Fix?  Seperate the mirrored meshes into seperate objects and then prior to copying the UVs,  flip the normals for the one's that would "break" (not the diagonal one because it "self-corrects").  After flipping the UVs, proceed with copying the UVs.  Then re-flip the normals back on the copies that needed this correction.

Tadaa!: 

 

[Copying node setup to another material]

Here's a helpful Blender Cookie tutorial on Youtube re: setting up Node Groups for your "library" of node set ups for append to future files.  It's a very nice workflow because with node groups  you are able to  can rename the input "sockets" and make it possible to  recall what the sockets are  controlling  and you can "isolate"  the specific inputs that you would like to access and change such as  textures or colors, etc.

[Multiple uv maps for one mesh object?]

Thanks very much for the correction Drongle. I was trying to be helpful and I may have made things clear as mud.

I completely blanked on the option to overlap UVs in the 0,1 UV grid since I rarely need that kind of resolution.  It however a very useful option.  In Blender at least,  you can assign each island to a distinctly seperate texture to bake to (I'm wondering if that's pretty universal in all UV packages), so its possible  at bake each islands high resolution AO texture for compositing without interference from the overlapping islands, (also assuming each overlaping island is also set up as a distinct material group so it's a distinct texture in SL.)  So I stand corrected. You can absolutely capture  the resulting AO  at a higher resolution then you would with a texture atlas type of UV set up where every thing is shrunk down so nothing overlaps.

I'm blanking here on whether in SL in the materials settings the bump and spec maps can be set individually for each texture/material group on a mesh or if a single "atlas" type map is required for the entire mesh.

 

Edited because I'm such a lame editor.

[Multiple uv maps for one mesh object?]

I hope is clear that you can only upload a single UV map per mesh into SL. Second LIfe does not support multiple UV maps.  

Assuming you want to bake the ao textures, bake a normal map, specular map etc. for use in compositing within PS or gimp,  you need to constrain your UVs within the 0,1 UV tile. And If you feel the lower resolution which would result from all these large parts sharing a single UV map is unacceptable you will need to break these items off as seperate objects and upload them that way as a linked group.  As seperate objects, again, each of these individual mesh can have a single UV map.

Each mesh can be assigned up to 8 materials and each material group represents a seperate texturable (actual word?) areas on your mesh - still just one UV map per mesh.  

[Mesh Wireframe (edges) changes upon upload from blender]

Some other options:

Select the Ngon and then insert (I).  Scale the inner ngon in a bit to create a border of faces and then remove the ngon.  Then select the boundry edge and press CTL F > Grid Fill.  (Note inserting is optional but it helps with shading.  Now with the ability to edit normals this might be no longer necessary)

Another option is to just select the Ngon and press CTL T  which will give you a trangulated result that has less of those troublesome thin elongated triangles.  Press F6 (or look in the left side transform palette) and toggle between the Polygon (means ngon) method of "Beauty" or "Clip" to get the arrangement you prefer.

[Fitting a UV map]

I think in this instance, where there are 5 star poles in the inner region the option to follow active quads won't work.  I could be wrong.

Another suggestion is to select the opposing boundry edges and "pin" them (shortcut p).  Then check live unwrap and then  boundry edges  and straighten which you can do by scaling to zero along the perpendicular axis of each selected edge edge in either the x or y direction.  The edges should straighten and the rest of the UV should conform. It can be tricky to do and without having the actual geometry to test this with, I can't guarentee that it will work in this case.  Worth a try.

 

Edited to add:  the "live unwrap" option is in the UV edit window under the menu "UVs".

 

Edited for clarity

[Blender & normal editing - rounded edges.]

Drongle, 

This looks like a terrific info, thanks.  

I did note you opened with: "Blender 2.5 is out."....did you mean Blender 2.75?

[Eliminating textures from UV dropdown list]

It's slightly interesting to filter the items list by "data block" and look at what's listed for images:

If there are images in the list, but none in the UV view, each will show 1 user.  

 

You can check "fake user" and make User jump to "2" and if you shift click on "X" as described before over in the UV window, the user number on this filtered list drops to zero.  Unfortunately I cannot seem to find a way to use this list to actually set this parameter to zero or to simply delete/remove the texture.

[Mesh Plane Trouble]

I forgot to also mention that to correct the problem:  Select all the faces and press CTL N to flip them to the outside.  If you are having difficulty with some faces not flipping to the exterior, then you may have "non-manifold" geometry which can happen with extruding, where a face is extruded inside your mesh (non manifold geoemetry is three or more faces that connect to one edge).  You  can quickly uncover such hidden geometry in edge or vertice selection mode with SHIFT CTL ALT M and then delete the offending faces.  Be aware that open boundry geometry will also be highlighted  when you use this shortcut (I'm not sure why),  so you need to take care that you don't accidently delete that boundry geometry.

[Mesh Plane Trouble]

It looks to me like your normals are flipped. If you are using blender there is an option to show polygons as doubles sided.  I always turn this feature off so I can see more clearly if I've accidently flipped the normals.  In the "N" Transform pallette, in the Shading sub-palette, check off "back faced culling"

 

[Eliminating textures from UV dropdown list]

If I'm understanding the Blender manual correctly, it's difficult for Blender to actually determine that an image is unlinked and then automatically dump it when you save the file  (like it does with unused materials that haven't been tagged with "F"/fake user.)  Apparently "Image Views" are counted as users.  I'm mystified by what "image views" might be and I'd appreciate it if someone could explain further.

 Quoting directly from the manual:

 

Removing Datablocks

As covered in Users (Garbage Collection), data-blocks are typically removed when they’re no longer used.

There are some exceptions to this however.

Scenes, text, can be removed directly.

Other data-blocks such as groups and actions can be Unlinked from the Outliner context menu.

Tip

Some data (images especially) is hard to keep track of, especially since image views are counted as users.

For data-blocks that can be unlinked - hold Shift while pressing on the X button, This force-clears the user-count, so the data-block will be removed on reload.

[Eliminating textures from UV dropdown list]

I agree. Selecting each unused texture in turn in the UV window then  holding shift while clicking the X to remove them followed by saving and reopening the Blend file has always been the way to remove unwanted unused textures.  

I find the process is much quicker when I then save the file with CTL S and then immediately click "Revert" from the file menu (note an little "double check menu" appears which is is easy to miss when you click revert) and Blender quickly replaces the screen with the revised version.  This takes just a second and *poof* those unwanted textures are gone.

[CAMPAIGN FOR A FAIR WAGE ON SL]

Your creative use of mixed fonts, text size, colors, "all caps", italics and boldface has convinced me you are passionate about this topic.

Perhaps every unhappy, unappreciated and underpaid  ("U.U.U.") worker in SL could protest by shutting off their computer and finding a well paid job in RL. (file that under: "who's stopping them?")   Or, alternatively, they might opt to spend more with their neglected cat.  Personally, the vast number of participants in SL who have an interest in such an activity would eagerly  D.J. for free just for the convenience of performing the job at home  sitting in their underwear in front of their computer.  RL D.J.s have transportation issues and wardrobe considerations to concern themselves with.

I suggest you watch this D.J. related video as recompense:  

 

 

 

 

[Is there a way to keep UV islands in proportion to the mesh?]

Ah! Well I'm sure many people would prefer to take the trouble to read the rotation angle from the bottom left of the screen before the rotation numbers disappear when you left click to commit to the rotation, then keep that in memory or jot it down, perform the transform and then type the numbers back in to reverse the rotation. :smileyindifferent: And I alternatively created custom orientations for this sort of thing.  However after I learned the technique I described from a Blender (Modo?) user forum post, I've found it simply quicker to, again, just rotate in object mode, edit in edit mode, re-enter object mode and snap the rotation back with" Alt R".  (In any event "never" is so very final.)  Here's hoping someone new to modeling and Blender will benefit from the tip.

(And being told repeatedly never to edit in Object mode consistantly screwed me up using the lattice modifier which, again, requires initial editing in object mode but NO application of the  object transformation with CTL A which would completely screw it up.  So frustrating for a beginner trying to learn to use these tools.)

[Is there a way to keep UV islands in proportion to the mesh?]

You wrote: " do as little editing as possible in Object mode, preferably none."

 

Here are two instances I know of where you might actually want to transform your mesh in object mode without applying rotation/scale and or location:

 

In the first instance if the geometry you want to transform is at an off-axis angle:

 

1) like this:

'

2) In object mode you can rotate the geometry temporarily so the vertices you wish to translate or scale align with an axis making it easier to transform.

3) Switch to Edit mode and perform the Transform action.

 

 

4) Return to Object Mode, press Alt R, and your mesh snaps back to it's original orientation.

(You can, alternatively, set up a custom orientation for this kind of edit, but I find the above method very fast and convenient.)

 

The other instance for editing in Object mode (and there may be others I'm not familiar with)  is when setting up a lattice modifier.  The lattice is scaled in Object mode to conform to the volume of the mesh it will be deforming.  Any editing in edit mode will deform the mesh so the initial scaling is done in Object mode.  in this instance, as well,  you do not apply the Object mode scaling with CLT A.

 

 

 

[Any advice on ways to line up UV islands for the different LODs?]

It's not particularly intuitive.  Press GG and begin to slide the vertex (it will distort the texture)  Immediately left click and press F6 to bring up the properties menu for this vert slide tool.  Check  "Correct UV's"  and go back and position the selected vertex.  This setting will persist until you change it back or start a new session of Blender, however perhaps it can be turned on and  then you can save a session with it turned on along with your start up file.

 

Edited to add:  This contradicts what I wrote previously in that I was under the impression the shortcut key combination "GG" had correct UVs was on by default.  Probably I forgot I used the CTL V command and set this previously when I tested it out.  After your follow-up post I figured out the left clicking bit by trial and error.

[Any advice on ways to line up UV islands for the different LODs?]

You wrote: 

 

"For yet others, such as vertex slide, it's not even an option. So avoid those unless you want to end up editing the UV map by hand."

I although vertex slide doesn't have that check box to "preserve UVs" like edge slide, I  found  sliding vertices with shortcut  "GG"  doesn't stretch/distort the texture previously assigned to those UVs.  It's as if the option to preserve UVS is built into vertex slide  .option - at least with Blender 2.74.  Please correct me if I'm wrong here.  Maybe my test of this on a subdivided plane was too simplistic.

[how to create these types of legs?]

Thank you so much for your generosity Drongle.  There is such a incredible wealth of modeling and material goodness in your postings here! And that gorgeous material.... I, for one, will be "forging" all weekend.  

[how to create these types of legs?]

Beautiful!!

[how to create these types of legs?]

I found a similar wish for two taper objects on a very old Blender Artist forum thread.  There wasn't much activity on that topic.

As a consolation prize I offer a link to the Curly Curve Add-on: 

http://blenderartists.org/forum/showthread.php?316651-AddOn-Curly-Curves

This is as close to a wrought-iron addon that I've come across

An interesting option to  using ALT S is to select a control point and press W>Set Curve Radius and then press F6 and set the radius numerically.  The nice thing about this option is it retains the number you input and the next time you select a control point and repeat the command it will reapply the last setting - or you can change it.  Nice for a consistant taper that follows a desired pattern.

[how to create these types of legs?]

I just noticed you wrote: "In 3ds max you can simply make a line, in any shape, then give it thickness."

In blender you can take a line (vertices connected by edges in Blender-ese)  and extrude it out to a shape, then in Object mode, press  the shortcut key combo ALT C to covert the line (mesh) to a Curve.  Then from the curve palette you can access the bevel, extrude, taper, etc. controls.  Probably a very similar feature to what you use in 3d Max.

I enjoy watching modeling tutorial videos done in 3d max. The users are very skilled modelers and there are many great videos on Youtube using 3ds Max   Over time I finally figured out (for the most part) the "translation" of terminology for many of the features/modifiers from 3ds max to what is similar in Modo and Blender.

[how to create these types of legs?]

 Or the use of the shortcuts:

Alt S to Scale up the curves geometry at selected points (in the Tools/Transform palette as Shrink/Fatten) and CTL T to Twist the geometry at any selected control points (listed in the Tools/Transform palette as Tilt)

[how to create these types of legs?]

If you've created the geometry from the curve in the curve palette (icon looks like a piece of macaroni) with the extruding and beveling functions, etc.,  then In object mode select the curve object and press Alt C  "Mesh from Curve" to convert the curve to a mesh.