# How do i Have GameObjects along a spline(Like Nodes)??

Hello i have been looking at Catmull Splines and i have been trying to create Gameobjects along the spline, while the Objects Face along the spline, to see what i mean see Pic1.

I can only create the spline which i learnt from [here][1].

Does anyone know how to do this?

-Pic1.
[75939-capture15.png*|75939]

And here is the code so you know what i have done.

``````using UnityEngine;
using System.Collections.Generic;

public class Spline : MonoBehaviour {

public List<Transform> controlPointsList = new List<Transform>();

public bool isLooping = true;

void OnDrawGizmos()
{
for (int i = 0; i < controlPointsList.Count; i++)
{
//Cant draw between the endpoints
//Neither do we need to draw from the second to the last endpoint
//...if we are not making a looping line
if ((i == 0 || i == controlPointsList.Count - 2 || i == controlPointsList.Count - 1) && !isLooping)
{
continue;
}

DisplayCatmullRomSpline(i);
}
Gizmos.color = Color.white;

//Draw a sphere at each control point
for (int i = 0; i < controlPointsList.Count; i++)
{
Gizmos.DrawWireSphere(controlPointsList*.position, 0.3f);*
``````

}
}
Vector3 ReturnCatmullRom(float t, Vector3 p0, Vector3 p1, Vector3 p2, Vector3 p3)
{
Vector3 a = 0.5f * (2f * p1);
Vector3 b = 0.5f * (p2 - p0);
Vector3 c = 0.5f * (2f * p0 - 5f * p1 + 4f * p2 - p3);
Vector3 d = 0.5f * (-p0 + 3f * p1 - 3f * p2 + p3);

Vector3 pos = a + (b * t) + (c * t * t) + (d * t * t * t);

return pos;
}

void DisplayCatmullRomSpline(int pos)
{
//Clamp to allow looping
Vector3 p0 = controlPointsList[ClampListPos(pos - 1)].position;
Vector3 p1 = controlPointsList[pos].position;
Vector3 p2 = controlPointsList[ClampListPos(pos + 1)].position;
Vector3 p3 = controlPointsList[ClampListPos(pos + 2)].position;

//Just assign a tmp value to this
Vector3 lastPos = Vector3.zero;

//t is always between 0 and 1 and determines the resolution of the spline
//0 is always at p1
for (float t = 0; t < 1; t += 0.1f)
{
//Find the coordinates between the control points with a Catmull-Rom spline
Vector3 newPos = ReturnCatmullRom(t, p0, p1, p2, p3);

//Cant display anything the first iteration
if (t == 0)
{
lastPos = newPos;
continue;
}

Gizmos.DrawLine(lastPos, newPos);
lastPos = newPos;
}

//Also draw the last line since it is always less than 1, so we will always miss it
Gizmos.DrawLine(lastPos, p2);
}

//Clamp the list positions to allow looping
//start over again when reaching the end or beginning
int ClampListPos(int pos)
{
if (pos < 0)
{
pos = controlPointsList.Count - 1;
}

if (pos > controlPointsList.Count)
{
pos = 1;
}
else if (pos > controlPointsList.Count - 1)
{
pos = 0;
}

return pos;
}
}

I’m not quite sure what you actually have problems with. If you just don’t know how to get the tangent of the spline there are two ways:

• get two points on the spline which are close to each other (“t” and “t + 0.001f”) and subtract the first from the second. This gives you a very good approximation of the tangent at the point “t”
• Calculate the derivative of the catmul rom spline equation and use that to get the exact tangent for a given point.

The derivative would be:

``````// spline:
// d*t*t*t + c*t*t + b*t + a

// tangent:
// 3*d*t*t + 2*c*t + b

Vector3 ReturnCatmullRomTangent(float t, Vector3 p0, Vector3 p1, Vector3 p2, Vector3 p3)
{
Vector3 b = 0.5f * (p2 - p0);
Vector3 c = (2f * p0 - 5f * p1 + 4f * p2 - p3);
Vector3 d = 1.5f * (-p0 + 3f * p1 - 3f * p2 + p3);

Vector3 tangent = b + c * t + d * t * t;
return tangent.normalized;
}
``````

This calculates the tangent for the given set of control points and the position “t” on that section of the spline. This tangent can be used with Quaternion.LookRotation to orient your objects so their z-axis points along the spline.

Here’s the same Gizmo code but additionally draw the tangents in yellow

You said you “learnt” that code from the given link but to me it looks like you just copied it from there. Are you sure you actually learnt anything from there? Do you understand the code? Even if you don’t understand the formula, do you understand what each of those methods is good for and how you should use them?

edit
If someone is interested how this continues, we have a follow up quesition in the help room.