I want to draw a nice transluent Polygon or Ellipse in rotation. 1) If I use -- glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); -- glColor4f(0.0f,1.0f,1.0f,0.5f); the object's borders are very nice, but transluency is not excellent. 2) but if I use -- glBlendFunc(GL_SRC_ALPHA, GL_SRC_COLOR); -- glColor4f(0.0f,1.0f,1.0f,0.0f); transluency is prefect but borders are awfull... Is there a way to combine both functionalities ???

Unfortunately I know no way to combine both. You could try the 'saturate' blending trick, but it requires an alpha buffer and I'm not sure it works with both antialiasing and traditional blending. Worth the try though.

If you want to anti-alias any generic scene, you might be interested in the multisampling feature. It requires a better hardware that polygon smoothing but also gives better results.