I've been digging and it's about as hard as I'd have expected to search for help on something simply named p! I rendered out a p image plane. It looks to be the same as a pointWorld pass in Maya, but I can't utilize it the same way. I usually use pointWorld to get a height map in Nuke but it doesn't seem to have a full range of data in the image. Do I have something set up incorrectly or is it meant to be used differently with Houdini?

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=89832&highlight=#89832 [sidefx.com]

If this makes no sense or sounds like I barely know Houdini it's because I barely know Houdini ) Trying to move over to it after years in Maya.

So, if currently, I'm making an image plane in my mantra node to save out a separate P image- what exactly am I rendering? To me, it looks like a pointWorld pass, but it sounds like it would need to be manually told to be changed over to world space in Houdini to use it as such? Wouldn't that mean that a default P pass is essentially a pointCamera pass? To switch it over to world seems like it would calculate off your camera by default.
Right now, I use Maya pointCamera passes to pull depth data and pointWorld passes only for height information. The P pass out of Houdini with nothing done to it doesn't have full data for either. If the image is always basically 4 rectangles of color with data in them (im generalizing here a lot!) everything works beautifully for the top half the image when manipulated. Below that Nuke doesn't see anything once I try to do anything to the pass.

So, after all that (thanks for bearing with me!) what really is a plain, no changes made P pass? And do I need to manually tell it to change to world space before render to get all the data I need?

I think by default mantra outputs position in camera space. If that's right and you need to get absolute world coordinates, you might want to create a different AOV in your shader and convert the coordinates from camera to world space using a transform VOP.

Cheers

Here's an example of how to export world position as a pass, just in case you're still wondering…

Cheers