# How to hit the trace on the back side of the mesh? **URL:** \ **Category:** Blueprint\ **Tags:** line-trace, unreal-engine, hit, question\ **Created:** [December 1, 2025, 11:29am UTC](https://forums.unrealengine.com/t/how-to-hit-the-trace-on-the-back-side-of-the-mesh/2680703 "2025-12-01T11:29:39Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Extrahdmi](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Extrahdmi](https://forums.unrealengine.com/u/Extrahdmi)\ **Post date:** [December 1, 2025, 11:29am UTC](https://forums.unrealengine.com/t/how-to-hit-the-trace-on-the-back-side-of-the-mesh/2680703/1 "2025-12-01T11:29:39Z")
I want the trace to hit the back of the mesh to measure the thickness of the object. How can I do this? There is a way to measure from the outside, but I want to measure the thickness of only a specific object without being obstructed by other objects. ---
**Author:** ![mteles-kokku](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/mteles-kokku/32/1185846_2.png) [@mteles-kokku](https://forums.unrealengine.com/u/mteles-kokku)\ **Post date:** [December 1, 2025, 1:44pm UTC](https://forums.unrealengine.com/t/how-to-hit-the-trace-on-the-back-side-of-the-mesh/2680703/2 "2025-12-01T13:44:45Z")
Here’s what I would try: After tracing from outside and finding the first edge, do a new trace from the endpoint of that first one, in the opposite direction. If the 2nd trace’s hit position is the same as its starting position, then you’re still inside the object. So go back to step one but use a longer trace. If it’s not the same, then the hit position is the outer edge, and now you can calculate the distance from the first trace’s hit position to the second trace’s hit position, which should be the thickness at the trace’s angle. All a bit theoretical though, I haven’t tried it myself. ---
**Author:** ![3dRaven](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/3draven/32/906552_2.png) [@3dRaven](https://forums.unrealengine.com/u/3dRaven)\ **Post date:** [December 1, 2025, 1:52pm UTC](https://forums.unrealengine.com/t/how-to-hit-the-trace-on-the-back-side-of-the-mesh/2680703/3 "2025-12-01T13:52:42Z")
If the object is rather uniform (for instance a wall without any ornaments) then you could get it’s locally aligned bounding box and get the dimensions from there > [@Object-oriented bounding box (from either AActor or mesh)](https://forums.unrealengine.com/t/object-oriented-bounding-box-from-either-aactor-or-mesh/326571): > > I’m using C++ and trying to do a sphere trace after an arbitrarily-sized projectile hits its target, in order to find the projectile’s entry point. For the sphere trace, I must know the radius of the projectile, which is dynamic and can be a rock, an arrow, etc. I’ve read about bounding boxes, and used GetActorBounds and other ways to get the bounds of the projectile, including getting an FBox struct from the mesh’s “Bounds” attribute, but bounds seem to be axis-aligned in all cases (AABB), whi… Edit: Did an extra trace on specific hit component with a flipped impact normal at a set distance as an offset along the normal’s direction. ![trace_thick](https://d3kjluh73b9h9o.cloudfront.net/original/4X/1/e/d/1ed88dbbc7a7ba2a3204b5dc57ae23386d19054a.jpeg) ---
**Author:** ![Extrahdmi](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Extrahdmi](https://forums.unrealengine.com/u/Extrahdmi)\ **Post date:** [December 2, 2025, 6:32am UTC](https://forums.unrealengine.com/t/how-to-hit-the-trace-on-the-back-side-of-the-mesh/2680703/4 "2025-12-02T06:32:46Z")
This is the first time I’ve heard of the existence of line tracing components! This is exactly the functionality I was looking for. Lots of normal line tracing is fine, but simple solutions are the best. I’ll put a vote on this.