Coloring polygons using GL.QUADS

Unity Engine
1

Hi,

I’m trying to color loops (polygons drawn with GL.QUADS) and it’s only working when the loop has 4 points.

Here’s a screenshot :

1763760--111704--Capture d’écran 2014-09-06 à 16.33.07.png

When there are 4 points, the loops is fully colored, but when there are more than 4 points, only one part of the loop is colored.

Here’s the function I’ve written :

public void ColorLoop(Loop l){
        // Color loop if closed, bool canColor is true and loops is not inversed
        if (l.isClosed() && l.canColorLoop && !l.isInverse()){
            float nearClip = cam.nearClipPlane + 0.00001f;
            Vector2[] points = l.getPoints();
       
            GL.Begin (GL.QUADS);
            GL.Color (l.getLoopColor());

            for (int i = 0; i < points.Length - 1; i++){
                GL.Vertex(cam.ViewportToWorldPoint(new Vector3(points[i].x, points[i].y, nearClip)));
            }

            GL.End();   
        }
    }

Any idea on how to color all the loop, even when it has more thant 4 points ?

Thanks !

2

QUADS stands for quadrilaterals, the fifth vertex will be interpreted as the first vertex of the second quad. For drawing polygons, triangulate them and then use GL.TRIANGLES.

3

Thanks for your answer. I found this Triangulator script : http://wiki.unity3d.com/index.php?title=Triangulator
This script is creating a mesh using a Vector2 array containing all the points of the polygon.

Anyone coud help me with this script and the one I’ve written to draw and color a triangulated polygon using GL.TRIANGLES ? :slight_smile:

4

This would be the gist of it:

  public void DrawPoly( Vector2[] points)
   {
     int[] indices = new Triangulator(points).Triangulate();

     GL.Begin(GL.TRIANGLES);

     for (int i = 0; i < indices.Length; i++)
     {
       var vertex2d = points[indices[i]];
       GL.Vertex( new Vector3(vertex2d.x, vertex2d.y, 0) );
     }

     GL.End();
   }

Drawing GL primitives this way is slower than using meshes, by the way.