Poor Vector3 decimals precision in subtraction C# Unity

Question

I want to know the direction a spaceship is actually moving to, its path of motion. I am doing it like so

void Start() { prevPos = transform.position; } void FixedUpdate() { Vector3 currPos = transform.position; Vector3 motion = currPos - prevPos; Debug.Log("Current position: " + currPos + " Previous position: " + prevPos + " Difference: " + motion); prevPos = currPos; }

The problem is that each frame the ship doesn't move too much, and the difference between currPos and prevPos (I'm guessing) is in the decimals (0.0530 for example). From what I read Vectors go up to 7 decimals, yet motion equals (0, 0, 0) most frames.

In the Debug above I get these results

Current position: (0, 0, 0.5) Previous position: (0, 0, 0.4) Difference: (0, 0, 0)

Programmer · Accepted Answer · 2018-07-08 14:14:56Z

The Debug.Log function is made to truncate Vector3 on purpose to make it more readable. If you need to show all decimals, simply make a function to concatenate and show each individual component of the Vector3.

void PrintVector3(Vector3 message, int type = 1) { if (type == 1) Debug.Log("X: " + message.x + " Y: " + message.y + " Z:" + message.z); if (type == 2) Debug.LogWarning("X: " + message.x + " Y: " + message.y + " Z:" + message.z); if (type == 3) Debug.LogError("X: " + message.x + " Y: " + message.y + " Z:" + message.z); }

Also when you concatenate string with Vector3, you also lose the decimal places. You can make a simple function to concatenate string and Vector3 an return the string. This string you can then print with Debug.Log.

string Concat(string val, Vector3 vec) { return val + " (" + vec.x + ", " + vec.y + ", " + vec.z + ")"; }

Yeah. You should create new question with the problem. Also add the raycast code and explain what's happening and what you expect to happen.
With the Debug.ray I wanted it to go from current position to previous position, so I used those arguments (currPos, prevPos...) but the arguments of that function are (from, direction...) and not from, to...
@RealAnyOne to compute direction just normalize the vector to - from.
The Debug.Log function logs whatever object it is given by calling its ToString method. It's the Vector3.ToString method that does the rounding.

IsMakeFire · Accepted Answer · 2021-04-23 22:48:40Z

As SilentSin points out, Vector3.ToString() is being called for you. If you call ToString yourself, you can control the precision of the rounding.

Debug.Log("Current position: " + currPos.ToString("N4") + " Previous position: " + prevPos.ToString("N4") + " Difference: " + motion.ToString("N4")); Debug.LogFormat("Current position: {0} Previous position: {1} Difference: {2}", currPos.ToString("N4"), prevPos.ToString("N4"), motion.ToString("N4"));

I find this useful for debugging as I can control the real estate claimed by each value.

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