I'm having a hard time figuring out how to create HDR textures with GIMP. Seeing as I can't save .exr files I'm getting the feeling it's impossible. I've tried picturenaut but it seems to be made for photography and I have no idea how to use it for what I need. I have a skybox with stars and all I want to do is increase their intensity a little beyond the standard RGB8 texture so I can make them shine using my game's bloom effect. I could change the luminescence value in my bloom shader but then the planets would start to glow...

I'm having a hard time figuring out how to create HDR textures with GIMP. Seeing as I can't save .exr files I'm getting the feeling it's impossible. I've tried picturenaut but it seems to be made for photography and I have no idea how to use it for what I need. I have a skybox with stars and all I want to do is increase their intensity a little beyond the standard RGB8 texture so I can make them shine using my game's bloom effect. I could change the luminescence value in my bloom shader but then the planets would start to glow...

You can't, the standard gimp implementation currently support only 8 bit channels. A common , simple trick is to use the alpha channel as glow mask (luminance = 1 + alpha * MAX_LUMI_VALUE)