Question Find point on the edge of a collider from the inside

Hey everyone,
I have quite a niche problem. I have a gameobject (with no collider) inside of a tilemap with collision. I want to be able to shoot a raycast from this game object and find the edge of the tilemaps collider. Is there a way to do this?
I've tried making the tilemap hollow on the inside but that causes physics objects to glitch through it sometimes.

Any suggestions would be appreciated!

Edit:
Here is an image of what I'm trying to do so that it is clearer since my explanation isn't very good:


The blue lines are raycasts that I am trying to shoot and as you can see, they travel through the tilemap collider, but stop when they leave the collision. What I'm am trying to find is the world positions of when they leave.
Hope this makes everything a bit more clear!

 

In what direction outward?

 

depending on your situation you may be able to get away with just switching the source and destination points of your raycast, so you aren't "shooting from the inside" technically

 

This would work but I don’t know the point on the collider that I would hit, that’s what I’m trying to find out from the raycast

 

It would be from the game object in multiple different directions outwards
the project is in 2D btw

 

If you're trying to find the closest collider, you could do a for loop with a spherecast centered on your character moving up towards the camera. Each iteration of the for loop make the circle bigger.

This way you get an expanding circle and can see which point it hit first, then of course stop the loop.

 

like i said, it depends on your situation, but if certain conditions are met, it should hit the same point. some conditions would be that you know the collision (if it were to occur) would be within X distance of the original source. another condition would be that there wouldn't be another hit picked up along that path. but imagine a world with just a single box collider. shooting a raycast from within the cube (at point p1) to anywhere (call it p2) should hit the same point as shooting from p2 to p1.

anyways, a better solution may be to just make your owns double-sided box collider composed of 6 box colliders (or an approximation of whatever shape you have). primitive colliders are a lot cheaper than they are usually assumed to be, especially when they are marked to not not interact with much around them.

 

Yes, I've used the "shoot from outside back to me" trick to simulate casting from inside of a box, and it works fine.

As far as avoiding other objects, a slimy trick is to temporarily change that one box's layer, and cast against only that layer. Or I think Collider.Raycast does the same thing (it's only capable of hitting the collider that called it) (that's if your 2D is using thin 3D boxes. If you're using Collider2D's than Collider2D.raycast seems to do a competely different thing).

 

Here's an image showing what I need to do, and hopefully that will make it more clear:


The blue lines represent the raycasts I would like to fire, and the origin of those raycasts is the game object. As you can see, there is a 'ceiling' that is part of the same collider (as this is a tilemap collider) so the "shoot from the outside back at me" trick won't work here. Really, what I'm looking for is a way to shoot a raycast that detects the absence of a collider rather than a collider in itself.

I understand that this may not be possible, but I hope that there is some solution that has the same effects. What I'm looking for is the position of those "collisions".
Thank you for your help so far!

 

Unfortunately that wouldn't work, if you look at the image in the reply above, you can see that I'm not trying to find the closest collider.

 

I think if you look at my edited question it will become clearer what I'm trying to do, as I'm pretty sure these suggestions won't work. Since I'm using a tilemap collider, I can't split it into smaller colliders. I also don't know the distance to the collision or where p2 is so the first method wouldn't work either.
Now that I've made my question more clear, do you haver any other suggestions?

 

Hey everyone, I think I've found the solution.

I set my tilemap to be used by composite, so that only the edges have collision, and now I can just check for collision with the tilemap. I didn't want to use this method before as it caused some objects to glitch through the map, but by changing the rigidbody collision detection from discrete to continuous fixed this.

Thank you everyone!

 

It you're simply pretending to raycast against a flat plane then often a math solution will work better. For example, ray intersection with a plane. Or you may notice a pattern in the results and without even working out the math as to why, write them in a table (as in, the lower-left corner is always (startX-0.621, startY-0.621, 1)).