Create a HDR image from a Maya scene?

Kyle_butler

From what I've seen, one of the most popular uses of HDR images is to compose live action plates with 3d models (matching light, reflection, etc). They capture it with a chrome ball in the time of shooting to later unwrap it and apply to the 3d scene.
My question is: if I want to create a HDR image from a 3d scene, should I create a chrome ball inside the program and render it?
There is an option inside mental ray that allows me to define the output format as a .hdr, but the result is horrible...

gray

before you can use hdr images you need to understand what a linear work flow is and how to use it. there are many tutorials on google. the maya documentation show you how to set up linear work flow in maya.

malcolm

You don't have to do the chrome ball if you don't want to, the IBL node in mental ray accepts a ball shaped map or a cross shaped map. Spherical or angular in the IBL settings. Looking at a chrome ball will give you less information because the wrap around parts of the image will have less pixels in them so I'd recommend a cross if you have the time to make one.

Making the cross can be done by hand in Maya by setting up 6 cameras each with a 90 fov pointing in each direction. You can then render each image as an exr or hdr, can't remember which one Photoshop can load. In newer versions of Maya 2012 and above I think you can preview the HDR image right in the render view and slide the exposure in real time after the render is completed so you can actually see what you're doing instead of guessing at brightnesses of light sources. I remember this not being straight forward to set up though and I can't find my notes on how to set it up.

ProperSquid

Not sure about HDR, but Photoshop can load EXR. Only issue is that the EXR files tend to look brighter on Photoshop. I don't expect that will have any effect on the files, though.

gray

if you want to view and edit hdr images get hdrshop, it was written by the people who invented hdr, and its free.

exr is more common now.

malcolm

gray I don't think hdrshop has been free for a while now.

gray

version 1 is free and capable for most tasks.

http://ict.debevec.org/~debevec/HDRShop/download/

Kyle_butler

Thanks for the answers, guys.
I ended up using a lens shader (latlong_lens) to create a panoramic image and rendered it out as a .hdr with RGA 4x32bit and 2K.
Photoshop opened the hdr file, no problems there.
Gray, I looked into Linear Workflow. I didn't know anything about it, thanks for pointing it out.