# Line Trace Behave Differently for Different Objects

I’ve been stuck on a problem for a while, and it actually took way more time than it should have for me to narrow the issue down to this, since it was so unexpected. I couldn’t find any answers online myself, though hope I’m not missing something. So here’s the thing:

I’ve casted a multi line trace from the right side of this image to the left side. It’s trace is gone here but it’s path was exactly the same as these red and blue lines. Now I’ve made it so that when this multi line trace gets a hit 2 times, a normal line trace gets casted from it’s hit location (that would be it’s 2nd hit location, which is the pillar on the left side of this image) to it’s start location. You see this first image of mine shows the expected result, the red line trace turns blue when it hits the pillar on the right side and a pink sphere gets drawn on it’s hit location. But that sometimes doesn’t work Take a look at this second image:

I’ve performed the same multi line trace on this one as well, it passed through the pillar on the right side and ended at the wall on the left side since it was it’s 2nd hit location. (Yes, there’s a wall there I made it transparent to clearly show that there’s no red line inside it) With the logic I’ve explained, left half of this blue line across the image should have been red until it hits the pillar, right? But it seems like the normal line trace’s red part already starts at the hit location! (well that obviously can’t be possible but you know what I mean, it hits very close to the start location)

I suppose the only difference between these two scenarios is that I’ve imported these pillars from Blender (please take your time getting amazed by my art, I know what can I say ) and this transparent wall is just a shape from the engine. Sure, their collisions might be different, I know these cubes also have a space diagonal as a collision line, it might be hitting some collisions from inside but that doesn’t make any sense! Like I said, the normal line trace that traces all the way backwards from the end location which is also the 2nd hit location of the multi line trace should already start on the outer side of any mesh, am I wrong? What matters should be their collision settings, which are exactly the same! To be honest, of course something must be different or I wouldn’t be facing this issue on the first place, but I can’t put my finger on it.

I hope there are some fellas whom I can get help from. So many thanks, all in advance!

Are you calling line trace by channel? Maybe check the collision channel on the objects make sure it’s consistent with line trace

Yep, the pillars from Blender and the invisible wall from the engine have the same collision presets, which are default

Oh no I was wondering why it doesn’t have that “Unresolved” text next to my topic but I think I’ve opened a discussion and not a question. Should I delete this and create a new question?

Check their channels though like if your calling a line trace on visibility channel and they’re on static it won’t work properly

I don’t think I understand. The objects I mentioned have default collision presets but should they be changed to world dynamic from world static? Why wouldn’t it work that way? I mean there’s a scenario that it does work.

Like I said, every single setting that shows up when I type “collision” in asset details window is the same between the working objects and the others. So what I’m trying to do already works when the normal line trace starts from the object that I’ve imported from Blender. But if it starts from a cube I created in Unreal, it shows the hit location as where it’s supposed to start, not hit. Very interesting…