OpenGL ES - blending of particle effect

Answer 1

If you have a normal ol' texture with alpha, and you're rendering in back-to-front order, this is the way to go:

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)

If your texture has premultiplied alpha, and you're rendering in back-to-front order, do this instead:

glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA)

Answer 2

From opengl.org

You might want to use the alpha values that result from texture mapping in the blend function. If so, (GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA) is always a good function to start with.

However, if you want blending to occur when the primitive is texture mapped (i.e., you want parts of the texture map to allow the underlying color of the primitive to show through), then don't use OpenGL blending. Instead, you'd use glTexEnv(), and set the texture environment mode to GL_BLEND. In this case, you'd want to leave the texture environment color to its default value of (0,0,0,0).