Devin Johnston Posted January 17, 2005 Share Posted January 17, 2005 Does anyone have any good tutorials for how to make an HDRI image? I've found a few but I would really like a detailed explanation on things like how big the Mirror ball should be, where it should be positioned, how far the camera should be from the ball, just all the technical details. Link to comment Share on other sites More sharing options...
Ismael Posted January 18, 2005 Share Posted January 18, 2005 Maybe this helps: http://www.hello-napalm.com/tuts/tut_hdri.html Ismael Link to comment Share on other sites More sharing options...
Devin Johnston Posted January 18, 2005 Author Share Posted January 18, 2005 I guess I'm kind of confused because there seem to be several ways you can produce an HDR image. One you can use a mirrored sphere and another is created by a panoramic image. I'm not sure which one is better or if one gives you more information than another? Link to comment Share on other sites More sharing options...
William Alexander Posted January 18, 2005 Share Posted January 18, 2005 I guess I'm kind of confused because there seem to be several ways you can produce an HDR image. One you can use a mirrored sphere and another is created by a panoramic image. I'm not sure which one is better or if one gives you more information than another? The Mirrored ball is restricted in resolution to part of an image. A true pano image is composed of at least 2 180+ degree fov images, much higher res. Using a pano stitching program you could use many many more images, really high res. High res is good for accurate reflections, cpu intensive for GI (typically a blurred lower res gives the best GI results). That tutorial is a bit misleading about the ball method, imho. It's not a true 360 pano image it's 180, half of what you might want for "realism", accurate room or exterior data. Half is better than none though. Getting into creating non-ball pano's can be quite an undertaking, are you leaning that way? WDA Link to comment Share on other sites More sharing options...
Devin Johnston Posted January 18, 2005 Author Share Posted January 18, 2005 Honestly I don't know, I'm going to have a photographer take all the pictures so I need to be able to explain to him how to do it. Were trying to do a perspective matched image and we want the lighting to be as close to real life as possible. I'm using Final Render for the image, and I've never used HDRI before beyond doing a few tutorials. It sounds like what I need is to have is the non ball pano done; can you give me some instruction on how to create this? Link to comment Share on other sites More sharing options...
derijones Posted January 18, 2005 Share Posted January 18, 2005 Essentially it is the same as taking a normal panorama, but at a heap of different F stops and then combining them in HDRI shop. I use Realviz Stitcher 3.1 (came free with 3D World mag a while ago). Workflow would be something like: 1. Using 18mm or so lens and a panorama head (http://www.kaidan.com or manfrotto) take say 10 exposures at a fixed shutter speed to cover from almost black through to almost blown out every 15 degrees or so to cover the full 360 globe (one straight down, one set at -45 elevation, one set at 0 elevation, one run at +45 elevation, one set at straight up) - this should give you some 740 shots - you need plenty of overlap between shots. 2.Using one set of 74 shots you can set up a template in Stitcher and then process the other 10 sets to get 10 lat/long shots, each one at a specific F stop. 3.Use HDRI shop or similar to combine these as per the reflective globe tutorial on the site to get the HDRI image. Finally - go to pub and have beer after all that work. There are a heap of tutorials on taking good panorama shots (google for quicktime VR, stitcher) and the tutorials on HDRI shop are pretty clear. I haven't actually done this right through to a HDRI, but the panoramas work well from a 3.2MP digital camera and the work of combining them in HDRI shop is pretty easy - I've used a reflective globe and it's pretty quick to get a useable HDRI. One problem with the multi shot system is changes in cloud cover etc - even with auto bracketting, I'd imagine things would have changed when taking 740 shots! Hope this helps - feel sorry for your photographer! Email me if things aren't clear. Cheers Deri Link to comment Share on other sites More sharing options...
Devin Johnston Posted January 18, 2005 Author Share Posted January 18, 2005 Man, that's a lot of freaking work! Is there an easier way of doing it, what about the mirrored ball? Link to comment Share on other sites More sharing options...
William Alexander Posted January 18, 2005 Share Posted January 18, 2005 with a 18mm lens & stitcher you really only need to overlap by 15-30 degrees meaning about 5-6 shots per f-stop, you can also use the full range of stops but in 5 increments. That being a total of say 30 shots. Manual apeture settings for the median light level. Good cost effective results But the pano rig is an absolute requirement, pivot center/s set to the proper adjusted focal piont of the lens. The ball method requires only 2 shots, front / back and those can be directly applied to a shpere through map channels....... to get the HDR GI/reflection. Not always perfect but quick and functional. Take care making sure that the images are taken 180 degrees apart and the camera is in the same plane. Even if the hdri's don't mate just perfect you can comp the GI'd subject into a touched up pano in PS comp or similar Both methods should work for a camera match & lighting situation if they represent the full 360 degrees of view. Cheers WDA Link to comment Share on other sites More sharing options...
Frosty Posted January 18, 2005 Share Posted January 18, 2005 There is another way , but be prepared to open the wallet. This is the same equipment used by Dosch to create their series of HDR images. Link to comment Share on other sites More sharing options...
derijones Posted January 18, 2005 Share Posted January 18, 2005 I thought you might say that! The ball is much easier: 1. Find a reflective ball - I got one from a company called Lakeland for £15 - it's actually a garden ornament - I think they're called "gazing globes" in the US. This shows up a couple of imperfections, but nothing that can't be tweaked in Photoshop if really required. 2. Fit the ball to a tripod or similar - if you can get one with a long neck (or a broom stick zip tied to a weighted down tripod) - it minimises the amount of clutter you see in the shot. 3. Set up your camera on a tripod and do the old bracketting routine - a telephoto lens is handy to minimise the size of the camera/operator in the shots - for better quality shots, take sets at 90 degree intervals around the globe - this will alow you to mask out cameras etc later and give you better coverage. 4. Follow the tutorials from Paul Debevec's site on sticking the images together to create a HDRI and masking out unwanted bits - it's a bit fiddly, but does work - there may be more advanced HDRI image editors available now. I've attached an JPG of the output from my trials - the black dot at either side is the result of not being able to see the back of the sphere - more than one set allows you to sort this out. Mounting the ball higher clears a lot of the clutter and shooting with a telephoto gets rid of the person - this was taken with a point and shoot digital - if it ever stops raining over here, I'll retake it with my new D70. You can also get some pretty weird photo's using the ball as well...... The skies work pretty well - they seem to be a bit rivher than the Dosch type ones (are they created in Terragen?), but watch out for stray bits of landscape creeping in if they are used out of context - I did a seaside building and had green fields visible out to sea - very embarrasing! Cheers Deri Link to comment Share on other sites More sharing options...
Devin Johnston Posted January 18, 2005 Author Share Posted January 18, 2005 It sounds like the ball is the way to go, I don't think I can justify the expense of 740 shots. If you take a picture of the ball from every 90 degrees then you would need a total of 48 shots made up of 4 groups of 12...right? I also have the Realviz Stitcher program so I guess I'm going to have to get it out and figure out how it works. How far back do you think the photographer should stand if he has a telephoto lens? Link to comment Share on other sites More sharing options...
derijones Posted January 18, 2005 Share Posted January 18, 2005 As far back as possible while keeping the full ball in the image - import all the shots in a set to layers in photoshop and crop them to a square - and make sure you have a very sturdy tripod - any movement between shots results in blurring and other weirdness. http://www.ict.usc.edu/graphics/HDRShop/ By a reflective ball and have a play - a couple of hours messing about should get you something useable. Cheers Deri Link to comment Share on other sites More sharing options...
bjornkn Posted January 19, 2005 Share Posted January 19, 2005 But how do you transform a standard rectangular format spherically (or cylindrically?) mapped image into that fisheye-like HDRI Lightprobe type? Is that also part of the HDRI workshop? BTW, it was mentioned that a reflection in a mirror ball is only 180 degrees. Why? If you look at the side of the sphere you'll certainly see objects that are far behind the ball. Theoretically, I think that if you have an infinitely small sphere you should be able to get a full 360 degrees view. I guess such balls are hard to find, and then you'd probably need a lens with infintely long focal length as well ;-) I've seen a description for making a mirror ball HDRI by taking one shot (bracketed) right ahead, and then one from the side at 90 degrees. That should solve the problem with the sphere's shadow, as well as the reflection of the camera/photographer? Link to comment Share on other sites More sharing options...
Devin Johnston Posted February 1, 2005 Author Share Posted February 1, 2005 Ok, our photographer has a camera that will take 360 degree images. I've attached the file but what I need to know is can an image like this be converted to an HDRI image? What kind of questions should I be asking him? Link to comment Share on other sites More sharing options...
Devin Johnston Posted February 1, 2005 Author Share Posted February 1, 2005 ftp://public@ftp.kirksey.com/FinalRender/untitled.mov Link to comment Share on other sites More sharing options...
jhaeusle Posted April 28, 2005 Share Posted April 28, 2005 Just wanted to add this adress for people interested in spherical panoramas and HDRI: short introdution and explanation about HDRI To see some Render-Examples, go to: Render Gallery or have a look at the following Panorama-PDFs: URBANbase SNOWbase SPRINGbase HDRIbase_Vol-1 HDRIbase_Vol-2 HDRIbase_Vol-3 Link to comment Share on other sites More sharing options...
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