Controlling the Transfromation Properties of a 3D Object With a Set Of Points

Allow me to elaborate, so I preprocess frames in python and extract a rectangle which roughly corresponds to the fretboard of the guitar.

I then send this position information to Unity to visualize it there.

Which works charmingly, though I also want to make my 3D guitar model fit the marked dots to the dots obtained through python, meaning that it should position, scale and rotate itself according to these points.

How can I achieve this?

I am fairly new to Unity and frankly have no idea how I can achieve such a feat. Has anyone done something similar before?

This is the ideal setup you want. You have two points X and Y as your targets, and you have reference points A and B on the guitar. O is the location of the centre of mass

First, set your scale.

// dist(X,Y) = scale * dist(A,B)
float scale = Vector3.Distance(posX,posY) / Vector3.Distance(posA, posB);
transform.localScale = Vector3.Scale(baseScale, scale);

You must know the base (initial) scale of the guitar. This is usually 1,1,1 but in some cases (like when importing from Blender) it tends to be something like 100,100,100 so just make sure you have the right values.

Next, you need to rotate the guitar. We can simply modify the guitar's transform.up.

Vector3 delXY = posY - posX;
transform.up = delXY.normalized;

Finally, you need to move your guitar to the desired position. We want A to coincide with X and B with Y. Let us just solve for A.

Vector3 movementVector = posX - posA;
transform.Translate(movementVector, Space.World);

The guitar should now be aligned with the rectangle.

A few things to note:

• The variables posX, posY, posA, and posB must be in world space
• We are assuming that the rectangle is on the same plane as the front of the guitar

That's all from me. All the best for your project. I hope this helped!