Vector3.Distance Inaccurate?

Unity Engine
1

Hi, I got a problem with a bunch of triangles I imported from blender. They are all supposed to be the same size. I’m trying to measure the vertices of each one with the following code:

		var dist1 : float = Vector3.Distance(oldverts[0],oldverts[1]);
		var dist2 : float = Vector3.Distance(oldverts[0],oldverts[2]);
		var dist3 : float = Vector3.Distance(oldverts[1],oldverts[2]);

		if (Mathf.Round(dist1*10)/10 == Mathf.Round(dist2*10)/10) {
			test = (i.TransformPoint(oldverts[1]) + i.TransformPoint(oldverts[2])) / 2;
		}
		if (Mathf.Round(dist2*10)/10 == Mathf.Round(dist3*10)/10) {
			test = (i.TransformPoint(oldverts[0]) + i.TransformPoint(oldverts[1])) / 2;
		}
		if (Mathf.Round(dist3*10)/10 == Mathf.Round(dist1*10)/10) {
			test = (i.TransformPoint(oldverts[0]) + i.TransformPoint(oldverts[2])) / 2;
		}

The problem is sometimes none of the if checks pass when one of them should always happen. Adjusting the rounding multiplier sometimes fixes it. Anyone have an idea how I can fix this please?

2

Beware of the float. Sometimes floats, doubles and ints don’t mix. Put in some prints in there to debug.

3

If your trying to check for approx difference, use Mathf.Approximately or if you need more control, do something like

if( Mathf.Abs( dist1 - dist2 ) < THRESHOLD )

I can see alot of problems with the rounding problems.

4

Beware of using Mathf.Approximately with iOS, it doesn’t work well. Go for Mathf.Abs instead.

5

I just had the same error as reported here with comparisons. Thanks for the thread. Solution was that i had initialised the distance to compare with a var dist = 9999; and then always selected the smallest one. That meant that Distance was being converted to an integer every time… make sure it’s not being turned into an int.

6

Another thing to keep in mind is that these comparisons are in object mesh space, NOT in the actual world space.

F’rinstance, if you have a scale factor of 2, then vertices that appear to be apart by X will only actually be reported as separated by X/2 by your calculations based on the vertex positions.