Polygon Triangulation And Layer Filling

[Simpkin]

Hi! I'm new here. Just started working with OpenGL using MFC. I've run into a problem when filling a polygons triangulated areas with different layers.

1st... I have a simple polygon (5 points in this example). I triangulate that polygon using googled methods to form 3 different triangles to fill. The polygon is in 3D and is a few layers thick.



When I fill the top layer transparently everything looks smooth,



but when filling any layer below it and moving the camera around in 3D space, I see the triangle lines between the layers.



My code is as follows:
glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glLineWidth(1);
////////removed code: here I draw the side quads for the 3d polygon
glBegin(GL_TRIANGLES);
for (j=0;j<tcount;j++){
const Vector2d &amp;p1 = triangulationresult[j*3+0];
const Vector2d &amp;p2 = triangulationresult[j*3+1];
const Vector2d &amp;p3 = triangulationresult[j*3+2];
glVertex3f(p1.GetX(),p1.GetY(), zValueForTopLayer);
glVertex3f(p2.GetX(),p2.GetY(), zValueForTopLayer);
glVertex3f(p3.GetX(),p3.GetY(), zValueForTopLayer);
//if i add this code here, i see the lines for the triangles
//glVertex3f(p1.GetX(),p1.GetY(),zValueForBottomLaye r);
//glVertex3f(p2.GetX(),p2.GetY(), zValueForBottomLayer);
//glVertex3f(p3.GetX(),p3.GetY(), zValueForBottomLayer);
}
glEnd();

How do I fix??

[Simpkin]

There must be some kind of setting... a blend function or something... that smooths those triangle faces to become one face for the polygon?

Here's some other settings I have in the openGL Init:

// Set color to use when clearing the background.
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClearDepth(1.0f);

// Turn on backface culling
glFrontFace(GL_CCW);
glCullFace(GL_BACK);

// Turn on depth testing
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);

[Aeluned]

Make sure GL_POLYGON_SMOOTH is disabled.

[Simpkin]

Still seeing the trianglation in the polygon with GL_POLYGON_SMOOTH disabled. (for reference I am drawing triangles, not polygons). I decided to go another route to graphically display the information I want (a solid color throughout), but for future projects I am still interested in a solution for this.

[Alfonse Reinheart]

How are you ensuring that the vertex positions are binary-identical?

[Simpkin]

I'm not even sure what you mean by binary-identical, but if you mean that they are the same numbers for a shared point of 2 triangles, the only verification I have is visual studio displaying them the same up to a certain decimal precision (5 points). These are floats. I tried casting all vertex coordinates into integers, and came up with the same result.

Is that what you meant?

[MaxH]

Have to ask - why do U triangulate the original polygon?
Why not use glBegin(GL_POLYGON) instead of glBegin(GL_TRIANGLES)?
That would be the first change I'd suggest.

[Alfonse Reinheart]

Binary identical. As in "float1 == float2" is true.

[Simpkin]

GL_POLYGON won't draw concave polygons.

[MaxH]

Is there any way your triangulation routine is working inconsistently on different layers? If you draw all the polys in wireframe, does anything look funny? Also, if you draw the bottom layer without drawing the top layer, does it look o.k.?