volumetric causing issues with alpha materials on other objects?


I’m still very much a blender newbie so hopefully someone can spot what I’m doing wrong here.

I’m building a scene (which will be animated as a kind of interactive map) where the camera and light source is inside a dyson sphere version of Earth (yes inspired by the Game Of Thrones title sequence). So we’ve got a lamp at 0,0,0 and a set of concentric spheres also at 0,0,0. Outermost sphere is Earth, then we have a sphere with a alpha image with place names, then another alpha image of clouds, and then a sphere with a volume material of clouds. The textures are from Natural Earth III, which is fantastic and free!

Whenever I enable rendering for the volumetric cloud sphere, the two alpha spheres become opaque.

I’m using blender internal on v2.68. Yes everything is set to receive transparent shadows. I could post a .blend file but it won’t be much use without the textures which are huge. I’m not using nodes for the materials / textures.

Please see the attached image for a demonstration of the issue.

Thanks for any help!