C# - Find Y coordinate given X value and slope (in degrees)

Unity Engine
1

Hello,

First time poster, pretty stumped right now as to how to do this because the way I’ve been told to do so does not work 100% of the times. Basically, I’m trying to create a random tree generator. This tree generator works, except that if I rotate the “Earth” (For now it’s only being rotated on the X axis), the trees still spawn with a Y coordinate of:

treePrefab.transform.localScale.y/2

(Above code works fine)

But if I take the “Earth”, and rotate it 45 degrees, obviously that would not work, as some trees would be underground essentially. So what I was doing was looking at what I knew and I know the X coordinate of the treePrefab, I know the Angle of the “Earth” piece, and I know that

tan(angle) = opp/adj

And that the Opposite is what the Y coordinate of the tree (Plus the treePrefabs y/2), then the value I need would be solved with the following equation

int yPos = Mathf.tan(angleInRadians) * xCoordinate

However int yPos is not what it should be. Help?

EDIT:
This is my complete, current code (as of posting this, no edits since)

using UnityEngine;
using System.Collections;

public class TreeGenerator : MonoBehaviour {

   public GameObject terrainPiece;
   public GameObject treePrefab;

   public int spread = 10;

   // Use this for initialization
   void Start ()
   {
     foreach (Transform child in terrainPiece.transform)
     {   
       float x = child.transform.localScale.x;
       float z = child.transform.localScale.z;

       float rX = child.transform.localEulerAngles.x;
       //float rZ = child.transform.localRotation.z;

       float tanX = Mathf.Tan(rX * Mathf.Deg2Rad);

       //child.transform.localScale.y/2 + treePrefab.transform.localScale.y/2

       for (int i = 1; i <= (x/spread); i++)
       {
         float posX = Random.Range(0, x) - (x/2);
         float posZ = Random.Range(0, z) - (z/2);

         float newX = tanX * posX;

         //print (newX);

         Instantiate (treePrefab, child.transform.position + new Vector3 (posX, newX, posZ), Quaternion.identity);
       }
     }
   }
   
   // Update is called once per frame
   void Update ()
   {
   
   }
}
2

I read this:

Ok… by random generator, random how so? What does the “earth” have to do with it? Do you mean randomly place on the surface of the Earth? What does localScale have to even do with that?

Wouldn’t you be adding those trees as a chlid of the Earth if they Earth can rotate? If so, the rotation of the Earth doesn’t matter.

What are you attempting to do exactly?

3

The “Earth” is just a 64x1x64 cube that can be rotated on ONLY the X and Z axises. I want the trees to randomly spawn inside the “Earth” (Meaning that they can only spawn “ontop” of the “Earth” cube). Now, since the “Earth” cube is at different angles on the X and Z, I’d like these trees to be touching the ground, not floating in the air.

4

Are you spawning them as children of the Earth? If so, they’ll inherit the rotation of the Earth. So you won’t need to adjust for it. Just set the ‘localPosition’ instead of ‘position’ (position being in global space).

If you’re not making them children of the Earth. Well then transform the point by the transform of the cube.