# Mesh generation error **URL:** \ **Category:** 3DEC\ **Created:** [November 30, 2021, 2:53pm UTC](https://forum.itascainternational.com/t/mesh-generation-error/129 "2021-11-30T14:53:27Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![jhazzard](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@jhazzard](https://forum.itascainternational.com/u/jhazzard)\ **Post date:** [November 30, 2021, 2:53pm UTC](https://forum.itascainternational.com/t/mesh-generation-error/129/1 "2021-11-30T14:53:27Z")
For _3DEC_ models with very ugly geometry, sometimes the very small or thin blocks cannot be zoned. You will see an error like this: **mesh generation error** **change specified edge length or split blocks** You can deal with this in several ways: 1. Do nothing. Leave the unzoned blocks as rigid and carry on. 2. Delete the unzoned blocks (only recommended for large strain analysis) 3. Give another BLOCK ZONE GEN command with a smaller edge length 4. Split the block(s) that didn’t zone (e.g. BLOCK CUT …) and try zoning again with another BLOCK ZONE GEN command. Use RANGE DEFORMABLE NOT to identify the blocks that didn’t zone. ---
**Author:** ![jhazzard](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@jhazzard](https://forum.itascainternational.com/u/jhazzard)\ **Post date:** [November 30, 2021, 4:05pm UTC](https://forum.itascainternational.com/t/mesh-generation-error/129/2 "2021-11-30T16:05:16Z")
As a follow up - if you decide to leave some blocks rigid, you may need to force the generation of subcontacts. This occurs automatically at the end of zone generation, but if the zone generation fails, you will need to do this by hand before assigning joint properties. Use the command BLOCK CONTACT GENERATE-SUBCONTACTS. Also, the rigid blocks will need to be assigned a density. So you will need a command like this: BLOCK PROPERTY DENSITY 2500 RANGE DEFORMABLE NOT.