Seemingly random results winding triangles?

Questions & Answers
1

Hello all.

First off, let me say I am new to unity, have some scripting experience, and battling UnityScript. Been pulling out what little hair I have left on this. I am working on a 2d game and the script I’m having trouble with is this pseudo destructible ground thing.

I Have a plane with a background image that has a scorched earth look to it, and a mesh that has a grass texture on it in front of it.
All this script is supposed to do is wind the grass mesh triangle clockwise based off of the index fed from a raycast so that it looks like the ground is dissapearing.

At tops this can only happen once every 4-5 seconds, so it shouldn’t eat up too much of the processor hopefully (mobile game). Eventually I want to have it wind the 2 triangles to the left and right (+ the 2 on the Z that I use for collision) of the raycasted index to make a little “crater”, throw up a few pieces of ground, but for the moment this is giving me enough grief.

So what’s happening is when I click on the mesh it will apparently wind whichever triangles it feels like. I am getting no errors (my syntax is improving I guess) but I have hit a wall…made of broken triangles. Here’s the code:

var triangleIDX : int = 0;

function Update () {

if(Input.GetKeyDown(KeyCode.Mouse0))
{	
	var hit : RaycastHit;
	if (Physics.Raycast (camera.ScreenPointToRay(Input.mousePosition), hit)) {
		triangleIDX = hit.triangleIndex*3;
	
		var meshCollider = hit.collider as MeshCollider;
		var mesh : Mesh = meshCollider.GetComponent(MeshFilter).mesh;
		var vertices = mesh.vertices;
		var triangles = mesh.triangles;
		var uvs : Vector2[] = new Vector2[vertices.Length];
		
		mesh.Clear();
		mesh.vertices = vertices;
		for (var i = 0; i < triangleIDX; i=i+3)
			{  
	        var tmp = triangles*;*

_ triangles = triangles[i+2];_
* triangles[i+2] = tmp;*
* }*

* for (i = 0 ; i < uvs.Length; i++)*
uvs = Vector2 (vertices_.x, vertices*.z);
mesh.uv = uvs;
mesh.triangles = triangles;
mesh.RecalculateNormals();
mesh.RecalculateBounds();
//mesh.Optimize();
}
}
}
Does anyone know what is happening here? I’m guessing its something like the triangle strips are throwing off the raycast, no idea really, but after reading what I could find in the reference about these strips…I am still pretty lost. Any help with this would be greatly appreciated. Thanks.
-Ads*
*update: Clarified question and updated code.
*Another code update_

2

I’m no expert on meshes, but the way I’m seeing it this is what this script does, correct me if I’m wrong:

  • It raycasts and finds a mesh
  • It then modifies and recreates that mesh
  • because of the nature of Raycast and user input, triangleIDX is going to be semi-random in nature
  • You are then swapping the first and third vertices of the triangles
  • Why are you only swapping the first and last? If you are rotating the triangle, wouldn’t you change the middle # as well?
  • why are you starting at i=0? Because TriangleIDX is semi-random, you are randomly going to affect somewhere between 1 and all of the triangles. Don’t you only need to touch the one found by the ray cast (i = triangleIDX; i < triangleIDX+3;i+=3)?
  • you then recalculate the UVs of the mesh (I assume correctly?)
  • and then you apply all your changes.

Also, it seems like the line:

if (!Physics.Raycast (camera.ScreenPointToRay(Input.mousePosition), hit))

  1. has a “!” when it shouldn’t – the if evaluates to true when nothing is found, and false when something is found? This seems like the code will throw a null pointer during runtime as is.

  2. is missing a “{” - causing the code attached to it to not be the code you are expecting. Perhaps it’s a typo from copy-paste?

I’m not an expert on meshes, so I’m mostly doing educated guess work trying to figure out what the code does.

3

Killing tris is going to leave hard-edged triangle shaded holes in your image. A cheesy way to also do that would be to “push back” the verts of the tri you hit, putting them behind the scortched plane and letting it show through. Ummm:

// logic: triangleIDX indexes the 1st vert in the hit tri.
//        traingleIDX+1 and +2 are the other two verts
//        o Maybe we could use barycentric coords to figure the closest one,
//        but easier to push all three back a random amount
//        o Assume scortched wall is 0.5 z behind us:

vertices[ triangles[triangleIDX+0] ].z += Random.value; // 0-1 pushback
vertices[ triangles[triangleIDX+1] ].z += Random.value;
vertices[ triangles[triangleIDX+2] ].z += Random.value;

The other way involves using the UV coords of the raycast hit to change the texture (either directly, or a system like Unity terrain, with grass, burnt and a “splat map” which changes with each hit and is used to mix them.)