Mesh/Exporting a mesh from Blender

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Revision as of 18:14, 11 September 2011 by Ashasekayi Ra (Talk | contribs)

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Video tutorial

Check out this 3-part Blender tutorial for static meshes.

There's also a detailed Blender rigging tutorial here: BlanderMan rigging tutorial part 1-1, part 1-2, part 2.

Simple tube avatar

Mancandy avatar

Basic workflow

Create a box (or monkey or teapot or hippo)

Reduce polygons

The easiest way to reduce the polygon count of your mesh is via the "Poly Reducer" script, accessible via the Mesh -> Scripts -> Poly Reducer. This script reduces the number of polygons in the model without affecting its shape, much like the "Decimate" tool, but also maintains the mesh's UV mapping.

To quickly and easily produce a set of LOD meshes:

  1. Make sure your blender file is saved
  2. Export your full-detail mesh to COLLADA
  3. Run Poly Reducer with a poly reduce setting of 0.5 (to reduce your polygon count by half).
    • If you make any manual changes to tweak the resulting mesh, remember to update the UV map to match.
  4. Export your mesh to COLLADA; this will be the "medium" level of detail.
  5. Reload your original full-detail mesh. It's good to start from the full-detail mesh each time to prevent errors from accumulating, though this may not be a significant concern for simple meshes such as attachments.
  6. Run Poly Reducer with a poly reduce setting of 0.25 (to reduce your polygon count by three quarters).
  7. Export your mesh to COLLADA; this will be your "low" level of detail.
  8. Reload your original full-detail mesh.
  9. Run Poly Reducer with a poly reduce setting of 0.125 (to reduce your polygon count by seven eighths).
  10. Export your mesh to COLLADA; this will be your "lowest" level of detail. You may also want to use this mesh when defining your model's physics.

Unfortunately the Poly Reducer script is currently only available for version 2.4x of Blender. The "Decimate" modifier is a serviceable substitute but the downside is that you'll need to redo the UV map for each LOD level.

Apply textures

Scale to meters

Scaling is somewhat arbitrary in Blender 2.49. In principle you just have to know how the mapping is between your 3D program (Blender) and the target environment (Second Life). Then all you need to do is to work in the correct scale. You even can later rescale your model in your target system.

So, what is the issue with Blender 2.49 ? It is all so simple that the Collada Exporter for Blender assumes that one Measurement Unit is mapped to one real life centimeter. But the common expectation in Second Life is that one Measurement Unit is mapped to 1 Second Life Meter. Unfortunately this missmatch very often leads to the import of "tiny objects". The common fix is to scale up the models in Blender 2.49 by a factor of 100.

But there is a nicer fix, which adjust the Collada Exporter to behave according to our expectations. See this video to find out, how you can fix the Measurement missmatch between Blender-2.49b and Second Life once and for ever:

If you don't want to watch the entire video:

find the file <blender script dir>\bpymodules\colladaImEx\ and change these two lines: = 'centimeter'
daeAsset.unit.meter = '0.01'

to = 'meter'
daeAsset.unit.meter = '1.00'

To find the scripts directory, do Help > System Information in blender, and look in the text file for "Default dir for scripts:". The path for me is:

C:\Documents and Settings\tapple\Application Data\Blender Foundation\Blender\.blender\scripts

and thus the file is:

C:\Documents and Settings\tapple\Application Data\Blender Foundation\Blender\.blender\scripts\bpymodules\colladaImEx\

Note that this fix is not needed in Blender 2.5x.

Export to COLLADA

Import to SL

Best Practices

Forum thread on optimizing your mesh in Blender for Second Life

Forum thread on installing Blender

Bones and rigging

It's possible to import one of the default BVH animations that can be found linked in the header of the Internal_Animations#User-playable_animations. This will get you a slightly inaccurate skeleton to work from.

Please note that the bones are all the wrong names for mesh import, as mentioned in Mesh/Troubleshooting#Rigging.

Forum tip for exporting joint positions with Blender

Gotchas and workarounds

Optimization techniques

Tutorial links

 ==  Blender 2.5x specefic ==

Second Life Rigged Clothing Series (available on HD)

How to Patch a Blender Python Add-on (available on HD)

How to Install Blender and Blender Addon Scripts (available on HD)

How to Use the New Bone Weight Copy 2.5x Script (available on HD) (has been updating his tutorials for 2.5)

==  Blender 2.5x SL Mesh Classes ==

Beginner SL Mesh Modeling Series

  • Class Level | Building: Beginner(2) | Blender: Beginner
  • Instructor: Ashasekayi Ra
  • Location: Builder's Brewery Pavilion
  • Time: Saturdays at 10 AM SLT