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JuRrAsStOiL
01-20-2006, 12:39 AM
Hi,

i'm about to finisch my Lamborghini Gallardo model and now i want to place it in front of
my house. I tried a single bitmap as environment, but it was ugly as it had a lag of detail
in the light information (reflections on the car looked flat).
So i decided to use a hdr-image. I have to create it myself, since i want to composite the
car into a photo i'm going to take in front of my house.

i already have hdrshop 1.0 for the creation, but my first tries look pretty crappy and they
don't look "complete".

Here are two images that should explain what i mean.

Example 01 (http://mitglied.lycos.de/jurrasstoil/example01.jpg)
Example 02 (http://mitglied.lycos.de/jurrasstoil/example02.jpg)

Do i have to take the photos for the hdr-image from 2 different angles to get a full hdr
panorama?

Anyone has a DETAILED tutorial on how to create an hdr-image with hdrshop?

Thanks a lot in advance.

AndreasMartin
01-20-2006, 05:57 PM
I suppose you can read German so take a look at the HDRI Handbook from Blochi (http://www.blochi.com/HDRI/). It's his diploma thesis and if I remember correct one chapter covers high dynamic range image creation with explanations for different techniques (one shot, fish eye, chrome ball, stitching etc.).

SirRender
01-20-2006, 07:05 PM
Check out this detail tutorial for more info:

http://myanimator.com/research/hdri_ibi/tutorial/

Zedman
01-20-2006, 07:18 PM
I usually only use one image, taken of a reflective ball (a 5cm polished steel bearing). The sphere will reflect everything in the environment, the full 360 degrees, except for the very small bit that is exactly behind it, and therefore not in view. There are two reasons why you might consider two shots: the part of the environment behind the ball is reflected in the ball on the outer circumference, and therefore is more low-res, and the fact that the camera (and the person taking the picture) is seen in it. I've tried taking two pictures from different angles, and it is just not worth it, it is very hard to stitch together the two images, even with a tripod, and supposedly exactly 90degree rotations. HDRshop can't do stitching, and the popular 2D photoeditors, afaik, can't open HDR files. That means you'd need to stitch together the original photographs. I usually use a series of about 7 photos taken at different exposures, that means you have to stitch the same scene 7 times, and make them match pixel-for-pixel. And *then* you can convert to HDR with HDRshop. So, it's not really worth it, especially if you only use it for lighting and reflections (ie: you don't need a high res panoramic background as well). And if you don't want to see yourself reflecting on the ball, then use automatic release shutter, and go hide...
I don't know of any detailed tutorials, though I've always wanted to write one, maybe in the following weeks, seeing I have more time, I can finally get around to do that.

JuRrAsStOiL
01-21-2006, 01:35 PM
Thanks a lot guys, this helps me out a little.

But i still have the most problems with hdrshop. The hdrshop-homepage isn't that detailed.
Most of the things they are describing skip some steps between. For example the Gamma
Curve Calibration. My results look totaly (and i mean TOTALY!) different.

When i use Panorama Transformation my mirrored ball should get stretched from an 1:1
ratio to 1:2 ... but it just gets a distorted 1:1 square. I did it like described in this tutorial:
http://myanimator.com/research/hdri_ibi/tutorial/
I already read the german handbook on hdri. I will try his way, but he kinda skips some
substeps too :(

I have an image series of about 14-18 images and when i load them into hdrshop and
assemble em it looks ok... but it still seems like it just covers 180. i will post a sample in a
few ours and some pics for your better understanding.

BTW: hdrshop talks about f-stops (shuttersize) and the most tutorials on hdri use
shutterspeed for their ranges... so whats "right"?

Thanks a lot again :)

Zedman
01-22-2006, 08:22 AM
The stops for shuttersize and different shutter speeds both do the same thing: let in more or less light, and therefore concentrate on one part of the dynamic range of the subject. One F-stop = 2 times more light, in the same way as neighbouring shutter speeds, like 1/30 and 1/60 also go in powers of two, so they are more or less interchangeable. There is one reason why the shutter speed might be a better option: if you change the aperture (shutter size), the way the image is focused also changes slightly. Ie: larger apertures let light through the outer parts of the lens, which leads to more errors, and a stronger depth of field, while small apertures have less depth of field blurring. So most people simply choose shutter speed, its simpler as well, my mid-range digital camera manages 1/2000 s to 15 s speeds, thats 15 powers of 2, more than you will get from aperture changes.

Okay, I though why not, here's a little mini tute for HDRshop:

For calibrating the camera curve:
- Go to: create > Calibrate camera curve. Click on slect image sequence. Load your images. Set the "Relative scale" of the first image to 1.0. And then set the following relative scales to, for exaple 2.0 if you used 1Fstops, or one step in shutter speeds. Or simply press the preset scale increments 1Fstop button on the right. Press OK
- Press Go, and wait a bit, until there is no more visible change in the three colour curves. If you select regularize, this will smooth out the curves (recommended), after turning it on, press reset, and the GO again. The little arrow at the right side, on the bottom of the curve view, can be dragged a bit to the left, so that your curves don't go through the roof in the very bright dynamic range. This also needs a Reset and GO.
- Save the curve.

Assembling the sequence:
- Create > Assemple HDR...
- Once again, load the image sequence, and set the Fstops. You can choose the "Calculate scale increments option", which actually does a pretty good job at guessing the relative stops.
- In the Camera response curve box, you can use the preset gamma curve (default exponent = 2.2), or load your own curve.
- Click on Generate Image.
- YAY! You have a HDR image, in the "mirror ball" format.

Conversion:
-Image> Panorama> Panoramic transformation
- Source image format: be sure to choose mirrored ball!
- Destination image: depending on the software you use, either a light probe (aka angular map), or latitude/longitude, or another one.
- I also sometimes apply some gaussian blur to the HDR map, and use that for lighting, as it will produce less artifacts (because of sampling) in the render, but make sure that if you see the beckground, then use the original, sharp, HDR.

hope this helps!

Varinder
03-11-2006, 02:12 AM
Im trying to make a light probe stand, the stand that'll hold the 'Light Probe/Mirrored Ball/Gazing Globe', whatever you wanna call it.

Does anyone have any 'homemade' tips on creating a light probe stand? Just something simple and sturdy, where you can just take out this stand, throw on the light probe on top of it and snap some pics of it to create the HDR image.

I'm lookin for ANY kind of tip or idea, could be like using a broom stick glued to a board on the bottom (which is what i'm using right now haha).

AndreasMartin
03-11-2006, 07:05 AM
Keith Bruns describes on his website a simple method to construct a mount for a reflective sphere.

http://img238.imageshack.us/img238/9075/hdrprobefullmod9lq.th.jpg (http://img238.imageshack.us/my.php?image=hdrprobefullmod9lq.jpg) Keith Bruns: How to build a mount for chrome Spheres
(http://www.unparent.com/page_galleryNew_DIYprobe.htm)

Varinder
03-11-2006, 07:53 AM
Hey Creative, that helped out perfectly, thanks a lot man!

I'm gonna try and make that this weekend.

I hope more people out there have some other ways of constructing a light probe stand and won't mind sharing.

MrBrick
04-06-2006, 10:30 PM
I just wanted to bump this for the good info in here.

This will help me on a project ill be working on in the summer.

biliousfrog
04-07-2006, 09:23 AM
have you actually looked on the HDR shop website? http://www.hdrshop.com/

it covers everything that you've asked for, how to take the photos, calibrate the camera curves, stitch two sets of images together (to remove yourself from the image), transform the image from reflective ball to light probe/cross/etc.....

for basic hdri compiling, Photoshop CS2 can do everything that you'd need, I use it all the time.

Varinder
04-09-2006, 08:02 AM
I finally got my hands on a 10 inch gazing globe and i was planning on creating that 'Keith Bruns tripod mount'. But, there is a moisture/rubber cap on the bottom of my gazing globe. I've read that your not supposed to take this cap off because it can ruin the chrome ball.

So I was wondering if someone has the same type of gazing globe i have and maybe figured out a way of how to create a sturdy tripod mount like Keith Bruns? Thanks.

UK3D
04-09-2006, 02:47 PM
Hi All,

I'm about to venture into the world of HDRI lighting and being a lazy soul by nature wondered if anybody had got good results by shooting a reflective sphere in RAW then used Photoshop CS2 to fake the different exposures? This would speed things up considerably and would solve the moving objects, skies, animals problem with multiple exposures.

Any suggestions? Ta Sean

ienrdna
04-09-2006, 10:30 PM
I know this is bit off topic but can somebody tell me what kind os camera I need too take HDRimages or some guide perhaps?

biliousfrog
04-10-2006, 03:06 PM
Hi All,

I'm about to venture into the world of HDRI lighting and being a lazy soul by nature wondered if anybody had got good results by shooting a reflective sphere in RAW then used Photoshop CS2 to fake the different exposures? This would speed things up considerably and would solve the moving objects, skies, animals problem with multiple exposures.

Any suggestions? Ta Sean


yes, I've been using a Canon EOS 300D. The only thing to watch is that PS doesn't auto correct the images, it generally auto exposes, colours, white balance etc. I just select them all, turn off the "auto" check boxes & select an appropriate white balance setting. Otherwise you'll get a really odd HDR image.

[EDIT].....I just re-read your question. It wouldn't work as an HDR image is made of multiple exposures, a RAW image just contains the exposure information so that it can be corrected. Load an HDRI into Photoshop & play with the exposure adjustment...the bright bits stay bright & sharp when you decrease the exposure....now try a RAW image, it doesn't have the same info so it just makes the image brighter or darker.

ienrdna, you can use anything that allows manual control over exposure or exposure compensation. I'm currently using a Canon digital SLR but have successfully used a JVC digital compact. The most important bit of gear is the tripod, if each exposure is in a different place the HDRI is screwed. Check out Paul Debevec's site & the HDR shop site...(debevec.org?) for guides.

Varinder
04-10-2006, 10:19 PM
I was curious about something. Is it ok to shoot the hdr images on another day from the shoot? Like say i shoot the film, outside today on a clear blue sky. And than i come back the next day and take the hdri shots of the gazing globe on a clear blue sky and at the exact same time as the day of the shoot?

Is this ok? Or would the hdr images not match up with the original film shoot?

rendermaniac
04-11-2006, 08:40 AM
It will be a lot more acurate if you can shoot it at the same location on the same day.

It has been known for people when asked to shoot a silver ball for vfx to just go into the car park on a different day - with lots of their mates hanging around in the background. Not much use to anyone.

And I know a silvered ball is a lot cheaper, but if you are going to be doing a lot of these a fisheye lens is far more painless.

Simon

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