I am investigating Global illumination rendering using environment maps and just viewed the Ambient occlusion tutorial for v 6.1. It mentions an image format that Houdini uses with the extension .rat . Does anyone have any knowledge of this format? The tutorial seemed to go through a conversion process using isixpack to convert an image from cross-shaped to lat-long format.
My main question is: Is is possible to use .hdr or 32-bit .Tiffs as enviroment maps if I convert it to Lat-long dimensions using another utility.. eg: hdrshop.
2nd part of this question is does the enviroment map setting in the VEX GI shop responsible for lighting and photon emission or just ambient occulsion and reflections.
RAT files are Houdini's internal texture format and they can support floating point images. You'll want to use them because they can be filtered and are a paged format. TIFFs cannot and are not.
Take a look at the file formats PDF for more info on RAT files.
.rat has everything you have in tiff or hdr and… much more, so you really want to use it thought you can use for this purpose tiffs also… but what for? - if rat is much better format for houdini - and it's similar to PRman tiff format in many aspects.
Click on the question mark icon in the upper-right corner of your houdini window. This opens up the help browser as a new side pane. Click on the links: User Guide Contents > Lighting > Global Illumination.
