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lwanmtr
10-18-2014, 08:03 PM
Hey...Was wondering if I could get some info on the differences between types of light probes....

Like whats the difference between .hdr and .exr?

I have some that look like panoramic shots and some that look like spheres....whats the difference there?

Any good tips on using them is helpful too.

Thanks

ernpchan
10-18-2014, 08:22 PM
Exr files have more to do with compositing. It's a file format that can hold multiple channels. I'm not sure what context an exr has in a light probe.

ernpchan
10-18-2014, 08:27 PM
For info on hdris I recommend this site. The book is a good read too.
http://www.hdrlabs.com/news/index.php

lwanmtr
10-18-2014, 08:42 PM
Thanks...ill check it out. I've been familiar with hdri...but downloaded some that were exr..though they seemed to work esactly the same in LW...so was just not sure of the difference.

m.d.
10-18-2014, 10:55 PM
Exr files have more to do with compositing. It's a file format that can hold multiple channels. I'm not sure what context an exr has in a light probe.

exr's are commonly used as they can do 32 bit floating point, are accelerated through all modern cards and are universally read....HDR is an older format with less support, but still pretty common

ernpchan
10-18-2014, 11:16 PM
Oh interesting. Good to know.

Greenlaw
10-18-2014, 11:32 PM
.exr is an image file format and it's not specially meant for lightprobes. I render nearly all animations in .exr because in addition to RGBA, the format can embed other data channels suitable for compositing, like motion vectors, depth, normals, object/material IDs, etc. As mentioned above, .exr just happens to be well suited for light probes because it supports high dynamic range.

The two images you described are a light probe (looks like a mirror ball) and a spherical map (looks like a panorama). The difference is in how they're shot but the usage is the same: they can both be used to cast light/reflection in a scene. Some tools require the image to be shot a certain way. For example, Image World in Lightwave expects the image that looks like it was shot in a mirror ball; Textured Environment expects the image that looks like a panorama.

If you're using the image for environment reflections, a spherical map works much better because the level of detail is more evenly depicted across the image.

For lighting and reflections, I usually just map a panoramic image inside an inverted sphere and use GI to emit from it--I find this easier manipulate the position/orientation of the lighting this way because I can see its relationship to the scene in the viewport. Certainly, it can get more technical than that--I just like to keep things simple and direct because of the tight deadlines I routinely face. :)

G.

lwanmtr
10-19-2014, 02:17 PM
Cool. Thanks for the info. Good to know about the difference between the two shapes also..I use image world alot, is good to know it like the roundy ones better...hehe.