I'm having trouble with decimation.

I have a mesh of a head. I wish to decimate to 10%, whilst keeping the ears at 100%.

So I create a Vertex group for each ear, and a third vertex group called foo for the remaining vertices.

enter image description here

It is this foo group I wish to decimate:

enter image description here

So far this is good, but if I lower the ratio below 0.3 it goes wonky:

enter image description here

Well, I almost have what I need. If I apply the same decimation again, that should reduce the detail sufficiently. i.e. 30% * 30% = 9% ~ 0.1 which is what I was after. But applying it twice, the second application gives another wonky picture the same as the one I posted.

Also, I shouldn't have to be sidestepping around weird behaviour I don't understand. Is it a bug, or am I doing something wrong?

PS I guess I can manually create a new Vertex group and decimate that...

  • $\begingroup$ I'm not sure I understood your problem correctly. Does the model decrease in detail/faces between .3 and 0? If not, is it possible you could upload your .blend? $\endgroup$ – gandalf3 Dec 15 '13 at 18:25
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    $\begingroup$ Hey, just FYI. Signatures and taglines are discouraged. $\endgroup$ – Daniel Pendergast Dec 15 '13 at 19:11

The ratio on the decimate modifier doesn't refer to level detail, it refers to the number of faces. From the wiki:

Ratio: The ratio of faces to keep after decimation, from 0.0 (0%, all faces have been completely removed) to 1.0 (100%, mesh is completely intact, except quads have been triangulated). As the percentage drops from 1.0 to 0.0, the mesh becomes more and more decimated until it no longer visually looks like the original mesh.


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