RaycastHit.textureCoord

Description

The uv texture coordinate at the impact point.

This can be used for 3D texture painting or drawing bullet marks. If the collider is no mesh collider, zero Vector2 will be returned.

// Attach this script to a camera and it will paint black pixels in 3D 
// on whatever the user clicks. Make sure the mesh you want to paint 
// on has a mesh collider attached.

var cam: Camera;

function Start() {
   cam = GetComponent.<Camera>();
}


function Update () {
    // Only when we press the mouse
    if (!Input.GetMouseButton(0))
        return;

    // Only if we hit something, do we continue
    var hit : RaycastHit;
    if (!Physics.Raycast(cam.ScreenPointToRay(Input.mousePosition), hit))
        return;

    // Just in case, also make sure the collider also has a renderer
    // material and texture. Also we should ignore primitive colliders.
    var rend : Renderer = hit.transform.GetComponent.<Renderer>();
   	var meshCollider = hit.collider as MeshCollider;
   	
    if (rend == null || rend.sharedMaterial == null ||
        rend.sharedMaterial.mainTexture == null || meshCollider == null)
        return;
 
    // Now draw a pixel where we hit the object
    var tex : Texture2D = rend.material.mainTexture as Texture2D;
    var pixelUV : Vector2 = hit.textureCoord;
    pixelUV.x *= tex.width;
    pixelUV.y *= tex.height;
    
    tex.SetPixel(pixelUV.x, pixelUV.y, Color.black);
 
    tex.Apply();
}

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public Camera cam;
    void Start() {
        cam = GetComponent<Camera>();
    }
    void Update() {
        if (!Input.GetMouseButton(0))
            return;
        
        RaycastHit hit;
        if (!Physics.Raycast(cam.ScreenPointToRay(Input.mousePosition), out hit))
            return;
        
        Renderer rend = hit.transform.GetComponent<Renderer>();
        MeshCollider meshCollider = hit.collider as MeshCollider;
        if (rend == null || rend.sharedMaterial == null || rend.sharedMaterial.mainTexture == null || meshCollider == null)
            return;
        
        Texture2D tex = rend.material.mainTexture as Texture2D;
        Vector2 pixelUV = hit.textureCoord;
        pixelUV.x *= tex.width;
        pixelUV.y *= tex.height;
        tex.SetPixel((int)pixelUV.x, (int)pixelUV.y, Color.black);
        tex.Apply();
    }
}

See Also: Physics.Raycast, Physics.Linecast, Physics.RaycastAll.