I can use langitude/longitude hdri maps as long as I'm not using it as a .rat file. Bit the efficence way is to use a .rat file and than I only can use a 6 cross image. So far I hope I have understand it correctly.

With HDRI Shop I can easily convert a l/l map to a 6 cross image but I don't have HDRI Shop.

Is there another programm or way to convert it?

roughsporty
I can use langitude/longitude hdri maps as long as I'm not using it as a .rat file. Bit the efficence way is to use a .rat file and than I only can use a 6 cross image.

Why you think so? You can use long/lat also in *.rat format. Rat doesn't force you to anything, it's just yet another (very handy) image format.

jeff wrote this post last year:

You can use lat long polar maps as environment maps as long as they are not our own .pic or .rat format.

It is best to use .rat files for texture maps (mipmap'ed images) in all cases. You need to use the command-line tool isixpack to create a proper rat environment map. isixpack takes either the traditional cross image or a series of 6 images that map to the standard 6 sides of a cube and builds a .rat image that contains six image planes each corresponding to front, right, back, etc… See the command line help for isixpack.

The hdri shop toolkit can easily generate the traditional cross image from light probe images. Then you use isixpack to convert to .rat files in the correct format.

You can download HDRshop for free to convert to vertical cross, then use isixpack to convert to RAT. It seems to put the watermark on your RAT file though, so i'm guessing the scene is partly illuminated with the houdini logo?

I didn't know you can use Lat/Long maps if they aren't rat/pic - thanks for the info.

I think Jeff meant cubic maps, which have to be rats, as they are deep rasters maned specifically. Or perhaps he advised you to use *.rat which is the best format for most cases in Houdini (though upcoming ptex might be better for env map), but it's not a hard limitation. You can illuminate a scene with long/lat map in any format the same way (projecting it on a sphere).

so, if I have understand you correctly, I can use l/l rat maps to project it on a sphere but also I can use it in the environment light as an environment map

mark2
You can download HDRshop for free to convert to vertical cross, then use isixpack to convert to RAT.

I have downloaded HDRI Shop the free version and loaded in al/l map but cannot find how I would convert it to a six cross?