Hopefully this will help people use the light probes, or create new ones. A light probe is fixed in Poser space. The center of the probe is located on the z+ axis, in the front of the scene. The rim of the probe is directly behind the scene or z-. The attached map will hopefully help people see how a probe will light their scene. Merd3D

Thanks Merd! (typo ;)

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That could come in handy for making artificial light probes, as opposed to ones created with an actual picture. Thanks!

Way too many people take way too many things way too seriously.

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Hmmm. Very good, Nerd. Face_off and I were just discussing how we thought images displayed light across a scene. This diagram is very useful. So... only the information contained in the circular data of that diagram is used in lighting a scene? What about on "flat" 2d backgroud-type images that are placed in the IBL channel of a light? The information that's OUTSIDE the circular area isn't used at all in the lighting solutions?

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Message edited on: 04/04/2005 17:29

AFAIK the area outside the circle is not used. For example the attached image, used as a light probe, is total blackout.

Nerd3D <-- Can't spell his name.

Message edited on: 04/04/2005 18:47

Thanks nerd. I would have thought the corners were the back, but I get blackness on frame 5 with this mat applied. Nice call.

Here's my contribution ;). Looks like there's not a lot of 'resolution' in the probing - it skips some colors all together. Scene was a simple hires sphere, one IBL light set to 100%. Map used is shown above, along with the view from front/rear/left and right cameras.

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Ok.. went to the material room and set the IBL Contrast from 3.0 (default) to 0 and got this new 'Right Camera' image.

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Here's the new Front camera image.

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..and the new Rear (back) camera image.

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Interesting.

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Watching with a lot of interest.... :) This playing with light has become a lot more fun.

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I will finally understand how the light probe works...

Thanks for this. I rendered a sphere with a mirror behind it using the lightmap shown above - and indeed - there was absolutely no light in the scene.

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Here's a free probe, my front yard. Just testing my Ligh probe making rig. About 2 PM looking east. Nerd3D

downloaded. Thanks Nerd. is that a straght photo of a shiny globe? a convex mirror? or? ::::: Opera :::::

It's a mirror ball. The camera and ball are hooked to a tripod. I use the timer so I can get out of the way. A little touch up to remove the camera from the image. An important point is that the probe rig was facing east, so the center of the picture is actually the west. Remember this is a photo of a mirror. It takes a bit of fiddling to correct the color of the ball. Uncorrected everthing looks way too blue, like it was taken in florescent light. Nerd3D

Oh, here's an image renderd with this probe and AO. I set the light intensity to 135% and turned shadows back on to get the ground shadow. I added 1 specular only light to get some highlighting back. AO images look kinda flat if you don't add some highlight back in. Nerd3D

Nerd3D, What diameter ball are you using?. I am considering buying a ball for making lightprobes, and there are several sizes available. I guess the larger the better (but one ball I found at 39 inches dia might be a bit over the top, and the cost would be equally huge.) Cheers Ian

I'd wondered whether you were dyslexic, or if the sun traveled backwards in your part of the world. ;^) But a photo of a mirror makes sense.

Where does one shop, is there a 'quality' issue, what sizes are optimal, what are they made of and what is a reasonable price. Sheesh, that sounded like a greedy teenager! ::::: Opera :::::

Operaguy, If you are in the UK, B&Q sell a 250mm 'Stainless steel sphere floating' as a garden pond ornament for about 17 which looks great in the catalogue, however the only example I have seen up close was so badly scratched and dented it would be useless for a lightprobe. I suspect somebody had been using it as a football :-( Ian

no, USA. The HDRI people must have info, I am going to surf and google.

I am a complete noob at lights and such but really need to learn. And I can see that I need it in my current work. So please excuse my no knowledge post.

Are there any tutorials 'light probes for dummies'? Where you get an understanding of the very basic like - what is it, how do you set it up, and such.
Would a panoramic render in Vue get an image similar to what is discussed above?

I don't know about the Light probe for dummies, but it really isn't that hard. My ligbt probe rig is made from a 10" diameter glass gazing ball found at WalMart. I don't remember but I bet I paid less than $10 for it. (10 incehes is about 30 CM for the metric folks) The camera is nothing fancy either. A little 3MPX job from Olympus. I made the rig so the ball fills the frame at maximum zoom. I made a steel bar then turned a socket from aluminum to hold the base of the ball. It holds the ball kind of like a glass light cover, with 3 set screws. This is bolted to one end of the bar. The camera has a mount on the other end. There is a 1/4-20 thread to mount it at the balance point. But! a duct tape an bailing wire rig will produce the same image quality. I made mine robust because I'm planning a "photo saffari" and I don't want to be struggling with the home made light probe rig. The camera and ball both fasten to my 25 year old "Focal" brand (That's a K-mart blue light special) tripod. The image I'm shooting are not HDRI. A camera that can do HDRI will set you back a few grand. It doesn't matter because I don't think any format that Poser can read will actually still be HDRI. I think that's why the lower contrast values work better for IBL light setups. The really high contrast values (5+) would bring out the extra range in an HDR image. A standard range image seems to works better with the contrast lower, 1 to 3 range. The images don't really need to be that high of resolution, unless you are doing some fancy gather-fake mirror-of-the-sky type render. In my test I could see no diffrence between a 1000px probe and a 100px probe in the final render. Would a panoramic render in Vue get an image similar to what is discussed above? Does the panorama render encompass the 360 degree view of the "world"? Then I guess it would work. Nerd3D

Nerd3D, Thanks for the info. Sounds like a really solid setup you have there. Did you take two shots at 90 degrees around the ball to eliminate the camera? If so how critical is the 90 degree angle? With a bit of luck I might have a mirror ball tomorrow so I will be able do practical tests instead of asking lots of questions. Cheers Ian

Doesn't a mirror ball only cover 180 degrees? And an IBL image is 360 degrees? Or have I missed the point here....

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A mirror ball will give you about 350 degrees. There is a little blind spot directly behind the ball. My light probe rig is very similar to the one they use here: http://www.debevec.org/Probes/ If you look closely at some of the probes you can see the photographer trying to be small, holding the camera. I went one step further so I can hide completely. I stand directly behind the ball in the "blind spot", or hide in a bush ;-) Nerd3D

I should add, that the source for an IBL does not have to be a light probe. Any image will do. You should have the light source in the shot. A nice panoramic sunset would probably work fine for a scene where the subject is supposed to be facing the sunset. You might want to photoshop a dark rim so the figure won't be too back lit. The map I posted at the top of this thread will be helpful for photoshopping an IBL source. Nerd3D

Caution. If you set one of these probes up on an IBL light, remember to TURN OFF SHADOWS for that light!

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ummmmmm why turn off the shadows? isn't the light supposed to cast shadows?

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IBL it attached to a light - but that doesn't mean the light is coming from the light - it's coming from the light probe file. So any shadows cast by the light itself if be invalid for the IBL file. So make sure shadow are turned off (but turn AO on). Interestingly, AO is light position dependent, so you can position your IBL light so as to get the right AO effects.

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ah, that's as clear as mud till I get my hands on P6 lol :D thanks for the explaination anyway :D

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That's not really true. AO is not effected by the direction of the light. If you turn it on for a diffuse light (A perfectly valid setup BTW) the back of the object will be darker, only because there is no light coming from that side, not because the AO calculation in effected.

Look at the image above. One Jessi is rendered with the light dead front. The other at stage right. Which is which? I can't tell either. One light, a solid white IBL with AO on.

Shadow can also be turned on if used correctly. It's really easy to get them right too. In the material room pick the IBL light. Look at the IBL image. See where the sun is? Setup the light so it's in the same place on the light ball. Now set the shadow level low, maybe .3 I usually use mapped shadows, but you can try raytraced shadows here as well. Either way you will probably wan to make them nice and soft with a blur of 2 or 3. In the picture of Leela above that is the setup I used.

Nerd3D

Nerd, maybe you are right.....Perhaps AO for IBL lights is not dependent on the light position. But I'm pretty sure (from experiments) that light position effects AO for Point/Spot and Infinite lights.

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**"... position your IBL light so as to get the right AO effects."**

Sorry, I thought we were talking about IBL. The position of an IBL does nothing for AO, or the placement of the probe image in poser space.

The other light types are a whole 'nother ball of wax. If you attach an image as the source of a spot, point or infinite moving it around moves the image too. The AO behavior is effected as well as you can see in the attached "shadow only" renders.

An interesting note is that the side shadowed image is from stage right. The shadows look backwards when you look at just the shadow. When you composite it with the diffuse image it makes sense. Areas that are in not lit do not receive the AO effect.

Nerd3D <-- Guess I beter put the nudity flag on now Message edited on: 04/07/2005 17:47

Nerd, that pretty much matches what I found. As a rough rule of thumb, AO from the front seems best.

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ok guys,,,,here is a NY probes for you...more if you like ~m

mstudios, thanks! is there a source of appropriate globes there in NY? or where did you purchase yours? ::::: OPera :::::

I create light probes, Operguy......why?

That is a great overcast probe, but my inquiry was about 'where does a person purchase the actual shiny globe' in order to make your own probes. ::::: Opera :::::

shiny Globes are steel balls....do a google online for metal balls....and find a supplier near you, then you can actually go and check the selection.... ~m

I also tend to use a 8mm fisheye lense....gives perfect circle and is easier than masking out the photographer.....there are articles online on fisheyes and where you can get them...NYC, adorama, B&H....and there is a supplier down in Atlanta ...kievcamera.com

thanks mstudios, especially that tip about the focal length and getting rid of the photog.

no worries... Even though I'm a high-end reotucher here in NYC, I tend to try and stay away from retouching things that don't need it....hence the fisheye lense...why go through all that when you can just turn around and photograph the backscene with a 180? fisheye? Same effect....less hassle. Anyway, love to see what you accomplish in your endeavours....keep us posted. ~m

This is fine for use as IBL sources, but if you are trying to match an envrionment it won't work. The shot needs to be as much of a 360deg shot as possible. Remember the rim of the shot is where the backlight comes from. mstudios example will work fine because it's a faily flat image, no focused light source, uniform placement if the contrasting elements. If this were a bright sunny day with dark shadows it would not work as well as a probe. Nerd3D

Nerd: You are right but you can use it as an Image Based Light image.....a nice bright contrasty image with lots of colour will work nicely....willadd the colours on the model...as if it were in the background.... As for Probes, you want a full HDR ( hi dynamic Range, not necessarily colour) ....my picture looks flat but has a full range 248. 235, 255 in the hi lites and almost 5, 7, 5 in the shadow end ~m

The background image ( a small jpeg) was used as the image in the IBL node on the main light in this picture. ..... why? 'cause I wanted the colour from the background to be globally introduced into the model..... ~m

Yeah, in my first expiriments with IBL that's what I was using. Just snap shots. That's what got me started trying to figure out how they were being handled. Here's a potential example If you wanted to use a square snapshot for an IBL source but the light source was way up in one corner you probably wouldn't get the intended results. The light in the corner would not get sampled. In a case like that a paint program that has a Polar Coordinate filter could be used to roll the image up in a ball. It wouldn't be exact, but at least the entire image gets sampled. Nerd3D

Attached Link: http://www.debevec.org/IBL2003/

I understand thoroughly Nerd3D::::

I went for using snapshots as well and now use 8mm lenses to shoot the backlight to the forground I use in my photo-composites. I then spherize them more to make them ( 180?) in Photoshop after reading Paul Debeve's articles ( see url above)

Thanx for all the information. The guys here are really good about sharing and I'd like to do the same....

~m

Message edited on: 04/09/2005 15:57

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Interesting. Very interesting!

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Forum: Poser - OFFICIAL

Subject: How Light Probes are Laid Out