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Old 23-01-2004, 07:46 PM   #1
kbrown
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Default K's MR Test Center =)

Right, some of you might recall the popular thread started by Undseth (former SM member) dealing with Mental Ray's features. I'll try to reawaken that tradition since I started (finally) playing with MR too.

My first conquest will be high dynamic range image based lighting. I went and bought meself a "custom-hemisphere-budget-hdri-mirror-ball-probe" for shooting the hdr image files (see figure 1a). Yes, it is a stainless steel soup ladle, which costed a whopping $6 .

So as my first test I shooted 12 images with different shutter speeds in my messy apt with my Panasonic DMC-LC5 digital camera. In HDRShop (www.debevec.org) I converted the images into a .hdr image (figure 1b). Also with HDRShop I converted the image from "Mirror Ball" to a "Latitude/Longitude" map (figure 1c).

In Maya I created a large polygon sphere, inverted the normals and assigned it to a lambert shader with the .hdr file in it's ambient color channel (Maya will complain about the .hdr files but MR does understand them so just ignore the warning). Inside that sphere I made another smaller sphere and mapped it to a fairly reflective blinn shader. The sphere is sitting on a plane which has it's own blin shader (figure 1d).

Finally I rendered the thing out using Mental Ray with PreviewFinalGather settings (figure 1e). For some reason I had to crank up the .hdr file's color gain from 1 to 60 (?!?). Don't know why but I will investigate this...
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Old 23-01-2004, 09:21 PM   #2
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Oh this is an awesome thread to start. I've been trying to figure out hdri lighting using MR as well. Your soup ladle idea is great!! I anxiously await your tests! :bgreen:

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Old 24-01-2004, 10:26 AM   #3
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kbrown if you're using maya 5.0 or lower, the mental ray renderer won't interprete *.hdr as High Dynamic Range images; you'll need a little commandline tool called "hdrtoxsi" (download the attachment) to convert them to *.map files.

since maya 5.01 you can actually use *.hdr and mental ray will use the full dynamic range
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Old 24-01-2004, 10:50 AM   #4
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hmm... thanks... damn... :/ yet another reason to upgrade... maybe i should finally max out my credit card :/
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Old 24-01-2004, 10:52 AM   #5
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damn? why's that?

[edit] ahh, you were faster

but that little tool really works nicely... the *.map files will work

and about the upgrade: maybe wait for 6?
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Old 04-02-2004, 08:59 AM   #6
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can you tell me how you did that? Is it a real envirement with that sphere planted in it using Photoshop ? Or Is that background part of that bigger surrounding thing??
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Old 04-02-2004, 07:17 PM   #7
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bastiaanwormgoor: I'm not sure what you're asking? I pretty much explained how I did it in the first post...
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Old 04-02-2004, 08:45 PM   #8
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hmm yeah sorry.. I hate it when people go ask questions that already have been answered and now I did it myself.. sorry..
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