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View Full Version : Cheap HDRI advice please!!

grrinc
11-20-2004, 02:45 PM
Hello Guys and Gals. Could you offer me some HDRI advice??

I am looking to start making some of my own HDRI images, and some how need to talk the missus into letting me buy a digital SLR. During the meanwhile, I have been toying with this idea, and was wondering if you could give an opinion. Here goes the build up first.....

I am assuming the reason an the image has to be taken with a sequence of F Stops, (as opposed to simply altering the brightness in photoshop) was so that the images would behave correctly in the reflection areas of the the model to be lit. If I am right here, then it wont be so important if the model has little in the way of reflection. Right??

So.......

Could I make an HDRI file using a panaramic picture stitcher like RealViz Stitcher?? As you can imagine I am also trying to avoid using a chrome ball (just my digi camera on a tripod), and then altering the brightness of each layer in Photoshop. Remember, reflections are not important.

If this is stupid, sorry for wasting your time!!

Thanks in advance

GRR
tweeeker
11-20-2004, 06:16 PM
By definition, doing what you suggest is not 'high dynamic range'. However, altering the brightness in photoshop is fine if the resulting image works for what you need. With a digital slr that supports raw images you can get a bit more dynamic range from a single photo, but then again, most also support at least 3 bracketed exposures which takes no longer to shoot.

Just to clarify about the reflections - do you mean you dont wish to use your maps to simulate specular reflections? HDR images are most often used to simulate diffuse reflections, where its still very useful to have the extra range. Having a hdr file helps to light multiple materials with different reflective properties with a single texture map. In general, its perfectly feasible to do it with regular low dynamic range images, but you'll need to a different exposure per material, so its kind of the same difference.

Does that help?

T
lehthanis
11-21-2004, 03:16 AM
And to answer your panorama question...

A regular panorama is not the same as a spherical panorama. and I don't know of any ways to convert from a stitched panoram to a lat-long that you need for your renders.

I wrote a cheapass tutorial that may help you take picture pieces and turn them into spherical panoramas though: http://www.deviantart.com/view/12379346/

but I can tell you from my recent toying with only a 2" ball its really fun to do the light probes in full HDR. its a rewarding challenge.
grrinc
11-21-2004, 10:37 PM
Chhers Guys for your help.

It is this that gave me the idea.

http://www.realviz.com/products/st/envir.php#essai

It is an expensive app so I may as well buy the slr camera and chrome ball to begin with.
Looks as though I have lots of homework to do. Thanks for the link as well.


Cheers
rebo
11-22-2004, 03:07 AM
get a Digital Rebel SLR and a cheapo steel ball (i got mine for around 10 US dollars), that will be a decent investment.
Andrew W
11-22-2004, 09:17 AM
HDRI the cheap and nasty way (http://www.andrew-whitehurst.net/hdri_tut.html) is the method I came up with about three years ago. Entropy and BMRT may no longer be with us but the concepts used are still current (and cheap!)

Hope that's of some use to you.

Andrew
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