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I have a blend file with really nice hard surface topology.

However, it's too detailleds. It's like a subdivision modifier was applied. I'm not sure if that is true.

enter image description here

I'm looking for an automatic way to reduce the dense topology while still keeping the "architecture" of the original topology (which I think is pretty good) intact. By "architecture" I mean that the geometry was started using primitives and not something like a 3D scan.

The goal is a low poly game model of around 2.000 triangles.

Here is what I imagine an automatic tool should do. I would like to remove like every 3 of 4 vertices.

enter image description here

How could this be done?

Here is the blend file.

Edit: I have tried to apply the suggestion of Checker Deselect, but I think the geometry doesn't allow applying it the way it was suggested to me:

enter image description here

How could I select the "correct" geometry to apply the Checker Deselect?

Thank you very much.

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    $\begingroup$ "reduce the dense topology while still keeping the original topology" it's not possible to have both, you either decimate or make retopo of highpoly and e.g. bake maps from highpoly to lowpoly or use highpoly. What is the final use of the model? $\endgroup$ – Mr Zak May 10 at 21:44
  • $\begingroup$ @MrZak Thank you. I have edited my post to indicate the purpose and what I mean by "original topology". $\endgroup$ – tmighty May 10 at 22:31
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Checker Deselect

You could use Checker Deselect and Dissolve Edges to get rid of this kind of pattern.

  • Select an Edge Ring. (Click Edge with Alt + Shift)
  • Choose Select > Checker Deselect
  • Set Parameters to Nth Selection = 2, Skip = 2, Offset = 0
  • Hit X for the Delete Menu and choose Dissolve Edges
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    $\begingroup$ Unfortunately the geometry isn't this simple, and it doesn't work. Instead of dissolving each 2nd edge, it remove the vertices completely for me. $\endgroup$ – tmighty May 11 at 0:45
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    $\begingroup$ You can go in parts with the Checker Deselect by hiding parts of the mesh, like the iron sides, before dissolving. Depending on the model, doing the Dissolve manually or using the above-mentioned Un-Subdivide might be the more economical option. $\endgroup$ – Ben May 11 at 9:24
  • $\begingroup$ Thank you very much. I will experiment now. $\endgroup$ – tmighty May 12 at 0:54
  • $\begingroup$ I have edited my post. I've tried your suggestion, but I don't think my geometry is "ready" for it. $\endgroup$ – tmighty May 12 at 1:15
  • $\begingroup$ I have seen a great suggestion in another question: Select a model part by using Ctrl + L, then Ctrl + E and then Un-Subdivide. Works pretty nicely!! $\endgroup$ – tmighty May 12 at 1:37
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For shapes like primitives and quad topology Decimate modifier set to Unsubdivide with even number of iterations could work.

enter image description here

Note though that this is very simple solution which has a lot of downsides.
In particular, it will behave badly on any surface similar to one filled with Grid Fill (note that there is triangle fan on the gif and it's for reason).
Also to mention is that Unsubdivide method doesn't have limit by vertex groups which means it will try to decimate everything in the given object and it won't perform quite well with uneven or more organic surfaces (you could of course split by objects which isn't always possible).
So this solution with modifier is generally quite task specific and might not work good as well in another scenario.

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