Bezier Curve, I am doing it wrong!

Hello, today I thought it would be neat to curve a line renderer, so I took to Google and a few hours later I think I have something...

Code (CSharp):

1.  
2. usingUnityEngine;
3. usingSystem.Collections;
4.  
5. [ExecuteInEditMode()] //EquivalenttoJS@scriptExecuteInEditMode()
6. publicclassBezierCurve : MonoBehaviour
7. {
8.  
9. publicGameObjectstart, control, end;
10. publicintnumberOfPoints = 20;
11. privateLineRendererlineRenderer;
12. privateVector3p0, p1, p2;
13.  
14. //Usethisforinitialization
15. voidStart ()
16. {
17. //Getthelinerendererattachtedtothescript
18. lineRenderer = GetComponent<LineRenderer>();
19.  
20. }
21.  
22. //Updateiscalledonceperframe
23. voidUpdate ()
24. {
25. if (numberOfPoints > 0)
26. {
27. lineRenderer.SetVertexCount(numberOfPoints); //Be sure to match the vertex count to the points
28. }
29.  
30. p0 = start.transform.position;
31. p1 = control.transform.position; //The control point helps shape the curve
32. p2 = end.transform.position;
33.  
34. for(inti = 0; i < numberOfPoints; i++)
35. {
36. float t = (float)i / (float)(numberOfPoints - 1);
37.  
38. //http://en.wikibooks.org/wiki/Cg_Programming/Unity/Bézier_Curves
39. //B(t) = (1-t)2 * p0 + 2(1-t)* t * p1 + t^2 * p2
40. //Be sure to check your Vector3 axis
41. Vector3position = (1.0F - t) * (1.0F - t) * newVector3(p0.x,0,p0.z)
42. + 2.0F * (1.0F - t) * t * newVector3(p1.x,0,p1.z)
43. + t * t * newVector3(p2.x,0,p2.z);
44.  
45. lineRenderer.SetPosition(i,position); //Assign each new position via for loop
46. }
47.  
48. }
49.  
50. }
51.  

As it stands right now, this thing will paint you a sweet pink straight line and not the awesome curve. I think I missing something, so I decided to post up what I have while re-going over the wiki. Basically line SetPositions don't seem to account for the control point, so the end and control are identical.

Okay, it was pretty late last night when I decided to type this up. The first thing I discovered this morning, my Vector3's were wrong. I was using x and y, not x and z. Since all of my points where zero on the y axis, I was only getting back a straight line. The script works perfectly now, just add it to a game object, and add a line renderer.

 

Im not sure how to interpret the square brackets in the algorithm, but your time calculation looks wrong.

I think it should be i/numberOfPoints (ie: value between 0-1 aka percentage)

It also looks like youre using the wrong points in your calcuation... looks to me like youre using p0, p1, p3 rather than p0,p1,p2 which is what the formula wants

 

Code (csharp):

1. float t = (float)i / (float)(numberOfPoints - 1);

If you don't cast those two int as float, you will always get 0 or 1.

 

Yeah, I should have caught that earlier.

 

I was under the impression that p1was the control point? Also, I found a much better article on the subject as it pertains to programming. I think every thing on this page is Java;
http://en.wikibooks.org/wiki/Cg_Programming/Unity/Bézier_Curves

 

looks like it has the entire code solution there for you...

 

AH, yeah thanks for pointing that out. Anyway, It's a little late here so I am headed to bed but I will post up what I got next morning. I also noticed the wiki uses a Vector3 straight up in their Bezier calculation, I tried breaking it up by X and Y, and then create a new Vector3 for it to work with C#.

I had my axis wrong in my Vector3's, new Vector3(x,0,y) hence the straight-line. I changed the code (above) so it shows the correct Vector: new Vector3(x,0,z). Also, I didn't realize you could multiply Vector3s in Java without specifying a particular axis.

Code (JavaScript):

1.  position = (1.0 - t) * (1.0 - t) * p0
2.          + 2.0 * (1.0 - t) * t * p1
3.          + t * t * p2;