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# Tesselation of Mono Connected Non Convex Polygon

, 6 Feb 2002 CPOL
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Tesselation of mono connected non convex polygon

## Introduction

A simple alternative to OpenGL polygon tesselation callback. You can focus on file triangle.h that contain the class to evaluate convexity of polygon and tesselate the polygon. No extra points are inserted. You can work only with planar polygon also in 3D.

Every suggestion in order to speed up the class and create better tesselation ('better' triangles) is appreciated.

## History

• 6th February, 2002: Initial post

## About the Author

 United States
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## Comments and Discussions

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 Found an index range error in code TruePyroman23-Feb-03 15:38 TruePyroman 23-Feb-03 15:38
 Re: Found an index range error in code topus10-Apr-03 3:46 topus 10-Apr-03 3:46
 Another litle improvement: Use previus code and change the line while( nVertex > 3 && bNoErrors ) with the line while( nVertex >= 3 && bNoErrors ) Also to solve the problem with degenerate points (alligned or sub-alligned) replace the test in function Triangle Area (that work fine for planar 2D polygon's) // // j is alligned from i to k ? // if( (-FLT_EPSILON) < m_A && m_A < FLT_EPSILON ) return degenerate; with: // // j is alligned from i to k ? // if( (-FLT_EPSILON) < m_A && m_A < FLT_EPSILON && (-FLT_EPSILON) < m_N[0] && m_N[0] < FLT_EPSILON && (-FLT_EPSILON) < m_N[1] && m_N[1] < FLT_EPSILON && (-FLT_EPSILON) < m_N[2] && m_N[2] < FLT_EPSILON ) return degenerate; Last (but not least) if some consecutive triangles as the same origin vertex you can optimizing opengl drawing code collecting the common side (from two consecutive triangles) and using triangle fan (example triangle vertex 0,1,2 && 0,2,3 etc.. can be collected in a triangle fan 0,1,2,3 etc..) Thanks very much for this very speedy code
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