Blending and lighting problems: the blending function doesn't work after rotation...


I am working for a 3D surface rendering. The rendering function works good when the rotation angle rotX(in x direction) and rotY(in y direction)
is between -90 to 90 degrees, when they are between 90 to180 degrees, the 3D object can not be blended…

the FOV is (-128, 128, -128, 128, 100, -100), the light is located at (128, 0, 0) and (-128, 0, 0)

Is any ideas or advise about this issue? is it a drawing ordering issue or just depending the lighting and blending function?
I am not sure why I couldn’t post the source code…

Thank you in advance!

drawing ordering issue

For blending to work correctly you must draw back-to-front from the camera view point.