Question Move Cube Along Curved Object

Hi everyone !

I'm trying to create this assembly line behaviour where the object is moving on top on another objects. My main problem is rotating and moving smoothly the object along the curve. You can check what I desire in following image:


I've tried two other approaches (rotateTowards and moving along the direction while rotating the cube on Yaxis). Right now, the transform.RotateAround is the one producing the best results but the transition from the curve to the straight rectangle isn't smooth and it's weird (because it rotates to fast when starts colliding with rectangle object).


To achieve this I'm doing the following:

Rectangles Objects:

Code (CSharp):

1.  
2. void OnTriggerStay(Collider other)
3. {
4.     var cube = other.gameObject;
5.     direction = endPoint.position - startPoint.position;
6.     cube.GetComponent<Rigidbody>().MovePosition(cube.transform.position +
7.     (direction.normalized * speed * Time.deltaTime));
8.     cube.transform.rotation = Quaternion.LookRotation(direction);
9. }
10.  

Curve Object:

Code (CSharp):

1.  
2. void OnTriggerStay(Collider other)
3. {
4.     var cube = other.gameObject;
5.     float angle = degree * Time.deltaTime;
6.     curveOrientation = -1; // -1 rotate to the left +1 rotate to the right
7.     cube.transform.RotateAround(pointO.position, new Vector3(0, curveOrientation, 0), angle);
8. }
9.  

I also thought in having the object following the tangent direction of the curve but at this point I don't have a clue on how to start. Sorry for the long post, I hope you can help me find a better solution for this problem.
Here's a small gif for better illustration:

 

well it does not rotate "too fast", it rotates instantly

thats because of this line:

cube.transform.rotation = Quaternion.LookRotation(direction);
this does not smoothly rotate the object, but instead instantly sets the rotation to look in the direction of the conveyor

which is exactly what happens in your video, it just jumps from being slowly rotated by the curve to being instantly rotated by the rectangle as soon as the corner of the cube touches the trigger of the rectangle

a solution would be:
- allow the cube to ignore the rectangles trigger while it is also triggering the curved object
- ensure that the curved object rotates fast enough to let the cube reach the orientation the conveyor wants from it (or dont let the rectangles object rotate the cube at all)

 

I use MegaShapes to do something similar in one of my projects. It has a walk loft component that allows you to move objects along the surface of a loft mesh. For example all the cows in this video are controlled by two float values one saying how far along the loft and the other how far across the loft

And another example where all the cubes and rocks use the same system.

 

Thanks for the insights!

Regarding the second topic of your solution, what would be the best way to ensure that? Clamp the rotation angle? Because if I'm correct, rotating too fast will also be a problem because the cube won't be facing the orientation of the conveyor.

I've to think about this.

@MikeUpchat
Thanks for sharing I wasn't aware of this asset. I'll look into it as last resort.

 

tbh nvm what I said there, since you are defining your rotation as a circular motion around point0, and your curve lies on that circle, you are already ensuring that you rotate the cube to meet exactly what the rectangle object afterwards wants

changing the rotation speed wont help there, i just didnt think my answer through there correctly ^^

all you have to do to fix your problem is to somehow prevent the rectangles trigger function to take effect while the curves trigger function is still moving the cube

one way to do this would be to:
give the cube a script like MovingObject : MonoBehaviour
which has a
public bool isBeingMovedByCurve = false;



than in your cuve script do:

Code (CSharp):

1. void OnTriggerEnter(Collider other)
2. {
3.     MovingObject cube = other.gameObject.GetComponent<MovingObject>();
4.     if(cube != null)
5.        cube.isBeingMovedByCurve = true;
6. }
7.  
8. void OnTriggerExit(Collider other)
9. {
10.     MovingObject cube = other.gameObject.GetComponent<MovingObject>();
11.     if(cube != null)
12.        cube.isBeingMovedByCurve = false;
13. }
14.  

with that you can simply change your rectangle object script to:

Code (CSharp):

1. void OnTriggerStay(Collider other)
2. {
3.     MovingObject cube = other.gameObject.GetComponent<MovingObject>();
4.     if(cube != null && !cube.isBeingMovedByCurve)
5.     {
6.        direction = endPoint.position - startPoint.position;
7.        cube.GetComponent<Rigidbody>().MovePosition(cube.transform.position +
8.        (direction.normalized * speed * Time.deltaTime));
9.        cube.transform.rotation = Quaternion.LookRotation(direction);
10.     }
11. }

which will prevent it being moved by the rectangle while it is still being moved by the curve

this should fully solve your problem

 

The board should not be used to drive the cube to move, because the cube may touch two boards at the same time
It’s better to use Unity’s own physical system to simulate this behavior

 

Ok I tried your suggestion and the result is better indeed but still not perfectly smooth !


Which got me thinking about your other suggestion regarding the line:

Code (csharp):

1. cube.transform.rotation = Quaternion.LookRotation(direction);

So I decided to remove it and the result is way better in my opinion however the cube after the curve is not fully aligned with the rectangle


Note: I also increased the rotation speed for both tests, previously was 5 degrees/second now it's 30/s which corresponds to the curvature angle of the curve.

 

Indeed, I'm aware of that but I can't see the issue there.

How should I do that? Could you detail more please ?

 

For the physics system you would steer the movement of your object using the rigidbody component it has attached, isntead of changing its transform directly

like to move your object
rigidBody.AddForce(<the direction it should move with magnitude being the speed>)
and to rotate your object you could do:
rigidBody.MoveRotatio(<the new rotation to which it should smoothly rotate>)

thus if the cube touches 2 conveyors at once, both will add up forces and 2 forces will pull at your cube at the same time (as I imagine you want It to)