# Reducing vertex density as distance from point increases

I have a 3-D mesh of a human head (mine!), ~100K vertices. I'm attempting to simulate soundwaves entering the ears.

The simulator's memory requirement shoots up as the vertex count increases by O(N^2)

So I need to massively reduce the vertex count. However, I need to keep the highest level of detail for the ears.

One approach might be to separate off the ears, and reduce the remaining mesh, then put it back together again.

Another approach might be to create a script that receives the xyz coordinates of each ear (maybe I can choose a point right at the entrance to the ear canal) and automatically merges vertices that far away from both foci.

Or maybe there is another approach?

Please do bear in mind that I've only ever use Blender once, and that was for something trivial: changing the file format of a mesh, so please don't hold back!

• I have a similar problem, but I actually want to do exactly what this question title requests. Neither of the answers quite address the question as posed in the title. I want a gradual increase in mesh face area / edge length as a function of distance from a point. Hope someone will add another answer to this question that describes how to do that. Commented Apr 7, 2016 at 2:36

If all you need is to reduce vertex count, and not care much about the topology, you may consider use Decimate modifier, and control the modifiable area by vertex group.

Method 1:

Method 2:

• Select the ears, then CTRLI to select the invert part;
• X > Limited Dissolve to dissolve elements for mesh simplification in a relatively cleaner way.
• Press F6 for further tweaks.

P.S.: Limited Dissolve gives same result as the Decimate Modifier by using its Planar mode. So you can use both.

(Head model came from Sintel project)

• Finally I've tried this out. Dissolve is no good to me, as I need triangles note n-gons. Decimate looks perfect, but it won't decimate in edit mode. And if I switch to object mode and then decimate, it decimates the entire model, rather than just the selected region...
– P i
Commented Dec 15, 2013 at 4:05
• You can easily triangulate the n-gons with a modifier or in edit mode. Commented Jun 5, 2014 at 10:24

Another option is to use Sculpting with Dynamic Topology.

1. Enter Sculpt Mode in 3D view > Header

2. Enable Dynamic Topology (CtrlD) in Tool Shelf (T) > Topology:

3. Set the brush tool to Simplify in 3D view > Header > Brush > Brush Tool:

4. Sculpt on the mesh to remove detail. You can adjust the Detail Size in 3D view > Tool shelf > Topology to change the level of detail the brush paints. Note that this value is in pixels, so it is view dependent. (The more you zoom out the lower the level of detail is)

Update: as of 2.71, there is now a constant detail option which is not dependent on zoom. There is also a detail picker, so you can set the detail based on the density of existing faces.

Example:

• Thanks a lot for this answer! :) It's the exact solution to my problem. Commented Apr 16, 2015 at 0:06
• This is great. In 2.79 Dynamic Topology is under Tools panel > Dyntopo Commented Jul 24, 2019 at 16:41