How can I get the X,Z value at a height of Y along a raycast?

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So I'm trying to get the X and Z position at which a raycast intersects at a certain Y level.

I'm using this in a base building system. The player is shown a preview ghost for the building section they want to place but I need the position from the raycast to position the preview ghost on the correct coordinates. I'm using some Y values as levels the player can place building sections on, so I want to use the Y values and the information from the raycast to find the point. I just don't know the math or functions to find this.

Answer 1

Answer by wideeyenow_unity · Aug 12, 2022 at 01:52 AM

You're gonna need to shoot the raycast from the camera, so documentation on all that is required for this is:

https://docs.unity3d.com/ScriptReference/Physics.Raycast.html

Also screen to world is very important : https://docs.unity3d.com/ScriptReference/Camera.ScreenToWorldPoint.html

and you'll probably also need to get familiar with collisions : https://docs.unity3d.com/ScriptReference/Collision-gameObject.html

Also might need to understand the Quaternions : https://docs.unity3d.com/ScriptReference/Quaternion.html

but mostly will need to know about positions : https://docs.unity3d.com/ScriptReference/Transform-position.html

and from the sounds of it, you'll need to know about colors : https://docs.unity3d.com/ScriptReference/Color.html

pretty sure there is something else, but it escapes me at the moment.. But you should be good to go :)

Ohh yeah, instantiations : https://docs.unity3d.com/ScriptReference/Object.Instantiate.html

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Ironwolf379 · Aug 12, 2022 at 06:33 AM 0

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I have everything like that working, I'm not completely new I just need the math for the raycast is all. Currently I have it working with detecting a collision with a certain layermask and checking if the object is a building area collider. But I want to remove having the colliders so I can have multiple building levels without having to check for which collider its hitting and so on. It all functions fine I just need help with the math but thanks anyway.

wideeyenow_unity Ironwolf379 · Aug 12, 2022 at 03:37 PM 0

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In the documentation on raycast, you should have noticed :

 if (Physics.Raycast(transform.position, transform.TransformDirection(Vector3.forward), out hit, Mathf.Infinity, layerMask))

The hit is what you're looking for, the hit.position to be exact. So not sure if you need a check of when hit.position.y is where you need it, or if you only want it to return if hit.position.y is where it should check?

I'm not 100% on understanding exactly how you wish to implement it. (sorry)

Ironwolf379 wideeyenow_unity · Aug 15, 2022 at 11:26 PM 0

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So I basically just want to shoot a raycast out anywhere from the camera and get the point at which it passes a set Y value. Without needing to use a collider to get it.

How can I get the X,Z value at a height of Y along a raycast?

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