HDRI inquiry

[djsmackmackey]

just curious, but how long does it take for an average HDRI 640x480 frame take to render? And if you could get an HDRI-like look without having to have the computer calculate any of the HDRI information (in other words, no radiosity or global illumination), would that be something most people would be interested in? Like say you could get a convincing fake of the HDRI look for matching live-action backgrounds, without really having to eat up computer memory, and possibly even save computer memory, would this be a really good thing, or not of much interest? Cause I'm working on a way to match live action lighting on CG objects for compositing that would pretty much do this. basically the computer would calculate the objects, textures, shadows, and specularity, so you could get away with only having one light only casting shadows, and one light only casting specularity and that would be it. you could use more than one of those lights, like if you wanted to make a dome of lights for overcast shadows, but it would be up to you. I've been testing it out and it takes roughly a few hours to set it all up, but each frame renders fairly fast. I'm using a 450 mhx P2 processor with 512 RAM, so I think it could be even better on a newer faster computer. And it's not a plug in or an outside program, it's all done within Maya, and can even be done on older versions of Maya. Anyway, just wanted to get peoples opinions on interest in this. Thanks.

[joojaa]

sure allways but...

It depends on what you mean by HDRI. HDRI is just the notion that while theres something called black color (absence of photons) theres no limit to how much light there can be (atleast in theory). But it seems that 3d people have totaly garbaged this notion in favor for HDRI meaning using HDRI images to as source for GI. But the implications are bigger than just that.

In theory HDRI hasnt anything to do with Radiosity or global illumination at all, HDRI refeers to the image format obtained (floating point with no max value), thisway you can more accurately calculate how lens effects bloom etc. But also incidentaly this info can be easily translated into good and accurate 3D lightning from your environment.

And yeah you dont need tu use expensi radiosity calculations to make the images look like this. In fact you shouldnt even contemplate on such things in any REAL production envinonment (go to www.pixho.com to see what i mean). You can achieve this quite nicley by even faking this. And untill i get 20-50 times faster performance than today i wont even consider full radiosity for production. But its still nice to have all sorts of nice stuff around.

[gdiman]

I've rendered simple scenes with HDRI image in a few minutes (less than 3mins) on a dual 1Ghz machine.

:::::vik3d:::::

[djsmackmackey]

yes, I've been to pixho.com. What my method involves it basically the ability to "light" a scene in 3d (at least in Maya), and not actually have any lights. lights would be used for shadows and maybe specularity, but not for illumination. I've been working on it for two years now and it's a bit of a process to rig, but that's a small price in my book, when lighting a scene for compositing into live action can take an enormous amount of time and it could still not be lit correctly. basically I capture lighting information from the real world and apply it to the 3D geometry to make a convincing match. I used the term HDRI just because that's what most people seem to understand. It isn't actually anything to do with HDRI, but more like image based lighting. I've looked around and as far as I can tell I'm the only one doing this, but for all I know it could have been done before. I don't really have the means or knowledge of other programs to try it out and see if it can be done in anything other than Maya. I'm sure it could be done if all the right nodes and capabilites were there. I'm not a programmer, I'm more on the artistic/creative side. So my solution may be just one big pain that could easily be simplified by somone who knew more about programming, but it works for me. I just don't know what to do with it now. Other than work on my demo reel using it. I could try creating a short and submitting it to Siggraph. I'm just worried by the time I'd get it done my method would be old news and HDRI rendering will be as common as raytracing, thereby eliminating a need for a fast rendering substitute.

[egor]

dl the sky.mel from highend..
you can do gi/hdri lighting with it , but with it you can also turn of the gi shadows and render you scene with hdri lighting very quickley

hope that makes scence?

[joojaa]

Yeah, plus this kind of lightning stuff has been around for a long time(i thinnk there vas a sigraph paper on this in 1999 or vas it 2000), and theyve even used this on real real photos of human faces (hultiple images of one face, and now they can relight it as they want).

[djsmackmackey]

yes, I know about the sky plugin. What I'm saying is that my method involves no lights unless you need shadows or specularity (which I usually just use reflection mapping for anyway). it's not a global illumination nor an HDRI render. I really don't know what to call it though. image based illumination? I dunno. I'll have to work on a descriptive title. but I can use my going on 4 years old computer that is only 450mhz P2, and render images in like 30 seconds at 640x480 using sub-d's characters. When I render a scene normally with lights and all, it can take 10 minutes per frame on my computer, depending on complexity. now, with my method, I've managed to cut that time down considerably. I haven't delved into using it for lighting an all CG scene yet, but I'm sure there would be advantages there too. I've only so far used it to light CG characters for compositing into live action footage. Whenever I get something done to demonstrate it, then I'll be able to reveal the process, because no one is really interested in it when I just tell them about it. but usually my friends wind up impressed when I show them a render and tell them it didn't use any lights.

[djsmackmackey]

I know. damn that forward advancement of digital technology! damn them I say! LOL
I just need to do some quick short flick to show it off. probably won't have a good storyline. just some 30 second thing.

[campbell]

yeah, put some produce on the table, then you might pique some more interest!

[stevesayer]

Have you looked at Mental Ray's final gathering options? It is the best image-based lighting I have seen, was great in xsi and now great in Maya.

It basically requires one point light set to 0 intensity to 'shoot' off photons, and then you create your env cube or sphere for instance with a texture map of the colours to light your scene on it. It renders in next no time at all, compared to using many lights.....and looks stunning. I am posting some of my renders soon.

It works even better with HDR images (converted to .map format so that MRay can read them) as the radiance values are used to give truer light intensities.

Image based lighting with Mental Ray has made me want to re-render most of my reel now!

HDRshop, a free plugin theat is used to create and manipulate HDR maps also has a plugin avalibale that generates a .mel script of a user-specified amount of lights based on the light values of the hdr maps, so if needed, you can import in a set of lights akin to a sky rig

Ben

[stevesayer]

I got all my info. from www.debevec.org. Paul Debevec wrote the papers you mentioned