I'm a bit lost here… I've been trying to learn how to use transparency maps properly in houdini, I have gathered from a post by stevenong that I should use a .rat file for the transparency map (thanks for posting the file with this) however I don't understand how to create a .rat file to be used for a transparency map.. I know to use the isixpack utility to compile them but I'm not sure I understand how to get the initial images from the base texture map that I have.. if anyone can shed any light on this or post a .rat file that can be used for a transparency map (I couldn't seem to get it from stevenong's file, just had it saved within the houdini file) I would greatly appreciate it.

Hey,

You don't need a .rat file for transparency maps. It should work as long as the image has an alpha channel in it or the shader has support for using luminance or individual colour channels.

More information about Random Access Texture (.rat) can be found here [sidefx.com].

Also, you're confused between creating an environment map from a cross HDR map with isixpack and converting any image format to .rat with iconvert [sidefx.com].

The file I used comes with Houdini. It can be found in $HFS/houdini/pic/ and there are other images as well.

Cheers!
steven

Edit: Added isixpack and iconvert paragraph.

Thank you for the info… well, I had been trying this with a .png file, I don't know enough about the different formats to know if this has an alpha channel (but I know .png's support transparency in some mannner) I will try to convert to the other formats to see if it works since with the .png it has been acting very strangely where its almost transparent but not all the way.

I'm guessing that the transparency map needs to be in one of the formats listed here:

http://www.sidefx.com/docs/houdini10.0/io/formats/image_formats [sidefx.com]

? (although some wouldn't work on there, such as .jpg)

I appreciate any further advice on this as this has been giving quite a headache the last couple of days

I think I've got it figured out as far as the conversion from .png to .pic.. pretty straightforward now that I've been playing around with it a bit.