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I am trying to add a transparent texture on top a cube. Only the front face is not transparent. Other sides are transparent. What could be the problem?. Any help is appreciated.
EDIT : I found that the face which is drawn first is opaque.
3 face of the cube is drawn.
Opaque face.((This face’s index is given first in GLdrawElements))
Transparent face.
You most probably ran into a sorting problem. To display transparent geometries correctly the faces of the object have to be sorted from back to front.
Unfortunately there is no built-in support for that in opengl-es (or in any gfx-library in existance). The only possibility is to sort your polygons, recreate your object each frame and draw it with correctly ordered faces.
A workaround would be using additive transparency instead of normal transparency. Additive transparency is an order independent calculation. You have to remember to turn off z-buffer writes while drawing because otherwise some geometry may be ocluded.
Additive transparency is achieved by setting both blendfunc values to GL_ONE.