[Csgl-users] tesselator how to?

[Christian B. <Ch...@be...>]

Hi, I'm trying to use the gluTesselator in CsGL but I'm somewhat confused
how to use it.
 
I am using the following code to tessellate (in my case a font glyph)
 
protected void GenerateText()
{
          CsGL.OpenGL.GLUtesselator tess = GL.gluNewTess();
          GL.gluTessCallback(tess, GL.GLU_TESS_BEGIN, new
GLUtessBeginProc(OnTessBegin));
          GL.gluTessCallback(tess, GL.GLU_TESS_VERTEX, new
GLUtessVertexProc(OnTessVertex));
          GL.gluTessCallback(tess, GL.GLU_TESS_END, new
GLUtessEndProc(OnTessEnd));
 
          GL.gluBeginPolygon(tess);
 
          GL.gluTessBeginContour(tess);
 
          foreach (CFreeTypeGlyph glyph in glyphs)
          {
                   double ratio = Math.Max(glyph.maxX, glyph.maxY);
                   for (int i=0; i<glyph.numPoints; i++)
                   {
                             int ix = glyph.points[i * 2];
                             int iy = glyph.points[(i * 2) + 1];
                             byte tag = glyph.tags[i];
                             double x = ix / ratio;
                             double y = iy / ratio;
 
                             double[] xy = { x, y };
                             GL.gluTessVertex(tess, xy, (IntPtr) 0);
                   }
          }
 
 
          GL.gluTessEndContour(tess);
          GL.gluEndPolygon(tess);
          GL.gluDeleteTess(tess);
}
 
Where my callbacks look like this...
 
public void OnTessBegin(uint type)
{
          GL.glPolygonMode(GL.GL_FRONT_AND_BACK, GL.GL_FILL);
          GL.glBegin(GL.GL_POLYGON);
          GL.glEnable(GL.GL_TEXTURE_2D); // this one is added 
          GL.glNormal3d(0, 0, 1);
          GL.glColor4d(1.0,1.0,1.0,1);
}
 
public void OnTessVertex(IntPtr data)
{
          // PROBLEM - DATA IS NULL!!!!!!
          // THIS CODE WILL THROW
 
          double[] vertex = new double[3];
System.Runtime.InteropServices.Marshal.Copy(data, vertex, 0, 3);
          GL.glTexCoord2d(vertex[0], vertex[1]);
          GL.glVertex2d(vertex[0], vertex[1]);
}
 
protected void OnTessEnd()
{
          GL.glEnd();
}
 
When the tesselator calls my OnTessVertex function though the "data" param
is null.  I guess I'm just using the whole thing wrong but I don't know if
it's my lack of understanding of OpenGL or lack of understanding of C# or
maybe both (which I would not be surprised).
 
Any thoughts on what is wrong with my code please?
 
Thanks,
-chris
 
PS. CsGL Rocks!