SteakOverflow - 5 months ago 29

C# Question

Unity 3D 5.4 allows to create a Matrix4x4, set its TRS values via Matrix4x4.SetTRS and multiply a point by that matrix to apply the transformation. I would expect the following code to print out the *translated* point but the translation doesn't seem to take place.

`m = Matrix4x4.identity;`

m.SetTRS(new Vector3(-10f, 4f, 0f), Quaternion.Euler(new Vector3(0f, 0f, 0f)), Vector3.one);

Vector3 P = new Vector3(10f, 1f, 0f);

Debug.Log("P': " + m * P);

The code prints out

`P': (10.0, 1.0, 0.0, 0.0)`

instead of

`P': (0.0, 5.0, 0.0, 0.0)`

Am I missing something?

Answer

To transform a `Vector3`

point using a `Matrix4x4`

, you need to use either `Matrix4x4.MultiplyPoint()`

or `Matrix4x4.MultiplyPoint3x4()`

. So in your case, I would try:

```
Debug.Log("P': " + m.MultiplyPoint3x4(P));
```

Also, as a tip - a `Quaternion`

indicating no rotation can be represented by `Quaternion.identity`

, so you don't need to keep calling `Quaternion.Euler()`

for that (if that was your intention).

Hope this helps! Let me know if you have any questions.