How to detect Merged vertecies / vertexes on the same Edge line in a Polygon

[Key-Real]

I render Polygons.
The situation is that I have a polygon which some vertexes are merged / vertex is on the same Edge Line, so i have a triangle.

Look at the image.
This Triangle is a 4 vertex Poly.

As it is, It will not pass the culling test and the rasterizer will drop this poly.


How to detect such vertecies?

[wp]

Iterate over the four vertices and check for equality?

[Key-Real]

yeh, that's what I'm fearing of.

I thought it would be a fast algorithm for that.

[wp]

Why is it important to find duplicate vertices? In the function that you posted in the other thread, duplicate vertices would simply add zero to the sum.

[Key-Real]

It still not working in some cases

see the image above

[Key-Real]

The Culling doesn't work only in NDC Space,

if it is not about the topic problem, I don't knew


EDIT:
 I had a DOT Product error in my calculations!
 I edited my post at the
https://forum.lazarus.freepascal.org/index.php/topic,64376.0.html

thread,
now everything works fine

[Key-Real]

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

PLEASE DELETE THIS THREAD!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!