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I downloaded Blur Weights addon, since it was made for blender 2.63 it is giving an error in blender 2.74 when trying to use it.

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Why does this error happens and how can it be fixed to make outdated addons to work with newer versions of blender?

Addon link

Denis
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    https://github.com/assumptionsoup/Blur-Weights/issues/1 someone has already offered a fix in the addon's issue tracker, you can apply the fix locally. or try the fork: https://github.com/zeffii/Blur-Weights – zeffii May 31 '15 at 05:42

1 Answers1

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This was added to speed up scripts. The Blender 2.73 release notes mention it and reference the commit that introduced it (in the Python API section)

A backwards compatible solution is the following addition before any code that accesses bm.verts / bm.edges / bm.faces indices explicitly. For clarity, that means if an addon has any code like this:

bm.verts[i]
bm.edges[i]
bm.faces[i]

Then preceding it must be a call to ensure_lookup_table. Often you'll only need to do one such call, and you'll want to stick it outside of any tight loops if possible. 

if hasattr(bm.verts, "ensure_lookup_table"): 
    bm.verts.ensure_lookup_table()
    # only if you need to:
    # bm.edges.ensure_lookup_table()   
    # bm.faces.ensure_lookup_table()

If you add new verts / edges / faces to the bm, and then subsequently do an indexed lookup you might find that you need to call ensure_lookup_table again.

zeffii
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