Damn decimator never work

As the title says: the decimator never work. Every time there is a text at the bottom saying: “Modifier error: Non-manifold mesh as input.” I tried it on about 3 models. I’m participating in the new low-poly contest at Threedy and the tri limit is 6500 so it’s kinda important.

try a cube, or a subdivided cube

a solid mesh is a manifold mesh, each edge has exactly two faces.

blender will tolerate edges with only one face in the decimator [say you delete one face from a cube], but will not tolerate edges with 3 or more faces [say you extrude one edge from a cube]

hit shift+alt+m to select non-manifold edges [these will be ones with 1 or 3 or more faces], and fix the areas that have 3 or more faces

then the decimator will work, but be warned… the decimator is nearly useless

Non-manifold means that some edges in your model have more than 2 faces attached to them. You can locate the non-manifold areas with a select->non-manifold and then delete the interior faces.


I tried deleting non-manifold faces on every project but i doesn’t work. Z3ro d I ain’t sure but do you mean I can only decimate box-models? Is there any other way to count the faces?

Is there any python script I can try instead?

I tried deleting non-manifold faces on every project but i doesn’t work

Select->NonManifold doesn’t select faces, it works only in edge/vertex select mode. Be sure to make a correct selection of the nonmanifold faces before deleting then

Tried that too. Doesn’t work. I really need it for this lowpoly contest.

It seems to work OK for me. If you still get an error of a nonmanifold mesh then there still are nonmanifold faces in your mesh. Be sure to delete them. Also do Remove Doubles.

I’ve tried deleting non-manifold faces 3 or 4 times so I’m pretty sure there is none left. I had no doubles.

If you Select->NonManifold, do they still show up or is nothing selected? Also to see the Decimation proces you must be in object mode. In edit mode you’ll only see the face reduction counter

Cambo has a decimation script called PyRedux.

If you use meshes that were not made with Blender you’re almost always going to have non-manifold problems. You might consider just using that mesh as a template to build your own lowpoly mesh from.


It is my model and it is low-poly.

I got it working with my KKK like reaper model. But I have a question what is it counting? Tris? Quads? Faces?



I know why it doesn’t work now. It can’t handle mirror modified objects.

It can’t handle mirror modified objects.

Just tried it with half a sphere. It can handle mirror modified opbjects. But you’ll have to use the mirror modifier (and not Alt-D, Alt-M) to get it work correct.

I tried mirror again and it worked then.

It doesn’t work again. I ain’t sure if I have understood right about the non-manifold faces. First unselect everything, then Space->Select->Non-manifold, then you press X->remove face (in vertice or edge mode.) Is that right? If I select non-manifold on one of the meshes that work it find some vertices, but the decimator work though.

Space->Select->Non-manifold, then you press X->remove face

This is correct, but it will only remove faces, if complete faces are selected. Since Select->Manifold only selects vertices or edges, not always complete faces are selected, and pressing X->Remove Face will not have the desired result.

I did not really understood what z3ro d said so can someone explain it in english what a nonmanifald mesh is cause I understood it like every face only could have one or two other faces connected to each other. Or could he have meant that every edge only can have one or two faces connected to it?