# Changing Inst Mesh Comp Transform results in inaccurate instance collisions

**URL:** <https://forums.unrealengine.com/t/changing-inst-mesh-comp-transform-results-in-inaccurate-instance-collisions/385205>\
**Category:** World Creation\
**Tags:** unreal-engine, Instanced-Mesh, Collision, Blueprint, question\
**Created:** [February 17, 2017, 5:23am UTC](https://forums.unrealengine.com/t/changing-inst-mesh-comp-transform-results-in-inaccurate-instance-collisions/385205 "2017-02-17T05:23:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Neilz0r](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Neilz0r](https://forums.unrealengine.com/u/Neilz0r)\
**Post date:** [February 17, 2017, 5:23am UTC](https://forums.unrealengine.com/t/changing-inst-mesh-comp-transform-results-in-inaccurate-instance-collisions/385205/1 "2017-02-17T05:23:17Z")

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Hi, I have been experiencing a very annoying bug and I finally decided to track down the root cause. Below, you will find a youtube video.

Scaling an “Instanced Static Mesh Component” results in inaccurate collisions for “Static Mesh Instances”.

Steps to recreate:

1. Create a new blueprint actor

2. Add an “instanced static mesh component” and then set the static mesh to something that is _not_ a perfect cube. I am using a cube mesh that is 1024 wide, 1024 long and 256 tall. This is important for properly illustrating the bug.

3. Here is a blueprint setup:

 ![126645-2017-02-16_22-00-50_ue4editor.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/6/2/a/62ad87058f339ec975add8355eb815184ef8786f.png)

Expected Result: The collision on the second static mesh instance should be rotated and scaled to accurately fit the visual result of the static mesh.

Actual Result: The collision does _not_ get scaled, and is merely rotated, resulting in inaccurate collision and the player can clip through the left and right side of the cube mesh.

Why I believe this happens: Setting the transform of an instanced static mesh component causes all subsequent instances to _potentially_ have inaccurate collision. Some instances will have correct collision while some will have completely incorrect collision and this depends on each instance’s transform values.

I have included a youtube video for demonstration to help illustrate the bug.

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**Author:** ![TJ\_V](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/tj_v/32/1008648_2.png) [@TJ\_V](https://forums.unrealengine.com/u/TJ_V)\
**Post date:** [February 22, 2017, 9:44pm UTC](https://forums.unrealengine.com/t/changing-inst-mesh-comp-transform-results-in-inaccurate-instance-collisions/385205/2 "2017-02-22T21:44:22Z")

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Hi CaptianMigraine,

Thank you for the report. I was able to reproduce this behavior so I’ve created [JIRA UE-42297](https://issues.unrealengine.com/issue/UE-42297) and our developers will be investigating further. Follow that link to monitor the status of the bug report.

Cheers,

TJ

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**Author:** ![Neilz0r](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Neilz0r](https://forums.unrealengine.com/u/Neilz0r)\
**Post date:** [February 23, 2017, 4:59am UTC](https://forums.unrealengine.com/t/changing-inst-mesh-comp-transform-results-in-inaccurate-instance-collisions/385205/3 "2017-02-23T04:59:31Z")

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Thank you!