decimate (collapse) bad results #37121

New Issue

Daniel Grauer · 2013-10-17T09:36:57+02:00

Daniel Grauer commented

2013-10-17 09:36:57 +02:00

%%%--- Operating System, Graphics card ---
os: windows 7 64bit
gpu: nvidia quadro k4000

- Blender version with error, and version that worked ---

error: r60797
working: dont know

- Short description of error ---

the decimate modifier creates some really nasty results with the collapse method. one would expect some behavior like the remove doubles function does so the mesh output is "usable"
see screenshot for comparison of the 2

- Steps for others to reproduce the error (preferably based on attached .blend file) ---

open blend file
select the object named "decimate"
play with the decimate modifier
notice the result is a mess

%%%

%%%--- Operating System, Graphics card --- os: windows 7 64bit gpu: nvidia quadro k4000 - Blender version with error, and version that worked --- error: r60797 working: dont know - Short description of error --- the decimate modifier creates some really nasty results with the collapse method. one would expect some behavior like the remove doubles function does so the mesh output is "usable" see screenshot for comparison of the 2 - Steps for others to reproduce the error (preferably based on attached .blend file) --- 1. open blend file 2. select the object named "decimate" 3. play with the decimate modifier 4. notice the result is a mess %%%

Daniel Grauer commented

2013-10-17 09:36:57 +02:00

Changed status to: 'Open'

Sanc Tuary commented

2013-10-19 00:03:35 +02:00

%%%That's probably because the decimate is trying to preserve the exact shape of the original model while lowering the vertice count.
While the model you obtain from remove double and increasing the merge distance does not look anymore at all like the original model (it has lost all its hard egdes as you can see and look smooth)

To see what i mean, take your original model, go to edit mode, select it all and click a dozen of time on the "Smooth Vertex" button, so your model lose its hard edges and become smoother.
Now use the decimate collapse and notice how the faces will now look more similar to what a remove double would do, because the model is smooth and the decimate does not have to preserve the hard edge look anymore.
%%%

%%%That's probably because the decimate is trying to preserve the exact shape of the original model while lowering the vertice count. While the model you obtain from remove double and increasing the merge distance does not look anymore at all like the original model (it has lost all its hard egdes as you can see and look smooth) To see what i mean, take your original model, go to edit mode, select it all and click a dozen of time on the "Smooth Vertex" button, so your model lose its hard edges and become smoother. Now use the decimate collapse and notice how the faces will now look more similar to what a remove double would do, because the model is smooth and the decimate does not have to preserve the hard edge look anymore. %%%

Daniel Grauer commented

2013-10-21 09:40:01 +02:00

%%%well i see what you are talking about but in a lot of scenarios a smoothing will change the mesh more than a uniform decimation would.
also the mesh slivers are a most undesired result where probably almost all artists would prefer a slight surface difference to bad triangulation.%%%

%%%well i see what you are talking about but in a lot of scenarios a smoothing will change the mesh more than a uniform decimation would. also the mesh slivers are a most undesired result where probably almost all artists would prefer a slight surface difference to bad triangulation.%%%

blender-admin commented

2013-11-27 01:26:19 +01:00

This issue was referenced by blender/blender-addons-contrib@3f5b59cd90

This issue was referenced by blender/blender-addons-contrib@3f5b59cd90c961d9737e7dbf8999c5030b7ccadf

blender-admin commented

2013-11-27 01:26:19 +01:00

This issue was referenced by 3f5b59cd90

This issue was referenced by 3f5b59cd90c961d9737e7dbf8999c5030b7ccadf

Campbell Barton commented

2013-11-27 01:27:13 +01:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue