Forum: Poser - OFFICIAL


Subject: Did e-frontier get the IBL light probe design wrong?

pjanak opened this issue on Apr 10, 2007 · 10 posts


pjanak posted Tue, 10 April 2007 at 11:10 PM

In other 3D apps I have the "sphere of influence" surrounds the object completely and is cut in half at the spheres equator by the scenes ground plane. As nothing matters below the ground plane. Does Posers IBL sphere behave the same way?. The example shown is how other 3D apps does it. For example, Truespace.

pjanak posted Tue, 10 April 2007 at 11:16 PM

Here4 is an IBL test ball image. I got the idea from reading how Nerd3D made a mirror ball rig with is real camera.   Thjis is just a high res sphere rendered in a scene within Poser. The idea naturally is to then take this spherical image and use it as an IBL source image. Only thing is that its faceing from the front.

pjanak posted Wed, 11 April 2007 at 4:29 AM

Or it may be that I am totally wrong. I didnt know it but apparrently there is an easy way to create an HDRI light probe image using multiple photos and a 360 panaorma stitching program


kuroyume0161 posted Wed, 11 April 2007 at 9:47 AM

There are several ways to make an HDRI probe image.  The key point of HDRI is in its acronym: High Dynamic Range Image.  The key isn't in the 360d environment, but in that the image stores more than just RGB intensities.  It also stores luminance intensities - from which it is possible to gain realistic lighting models applied to the 3D scene.
Most HDRI is applied fully spherically.  Truespace seems to be making unqualified assumptions if that is how it does this - maybe there are options (?).

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

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pjanak posted Wed, 11 April 2007 at 11:20 PM

I hadn't used trusespace in a long while but what I recall is that when you choose to use an IBL light. a 3D sphere is displayed in whole. But with the lower half unused from what I gather. Its also positionalble. Thats the one thing I really hatre about poser they don't have light cone reprentations for the spot lights or even a sphere for the IBL to inform you how the image applied to it is oriented.

You're right I hadn't considered the my 3D environment wasn't going to deliver that whole dynamic range. I didn't realize it but it seems Photoshop has built in panorma sticthing and the ability to geberate an HDRI image based on different excposures of the same image.

But just to play around Im going to render differnt camera positions and stitch them into a 360 spherical view. Then I my do the same at different light intensities. Just to see what I get.

Pete


kuroyume0161 posted Thu, 12 April 2007 at 12:01 AM

Poser's IBL is problematic in the directional sense - you can rotate the light with the light sphere, but it is guesswork as to where the positions are.  The one thing that I like about Cinema 4D's is that you map the HDRI onto a sphere which is then positionable and rotatable to get the desired results.

Don't have the version of Photoshop with HDRI, but that is an excellent place to stitch and generate it I would suppose.  Are you faking the intensities by saturation or do you have a separate set of greyscale exposure photos?

Best of luck with your experimentation!  I haven't had the luxury of time to devote to actually doing my own HDRI images - would be cool to take the panorama or mirror ball all the way through.

One thing to note about Poser - there is HDRI in Poser 7, but only IBL in Poser 6.  These are slightly different approaches.  IBL is basically HDRI without the H. :)  It uses the standard RGB to do the lighting.  So I'm not certain if the HDRI is applied to the scene in the exact same way as the IBL - might be.  In that case, you do get the full spherical surround but, as noted, not the graphical control.  I do all of my HDRI and GI in Cinema 4D as Poser is too slow and quirky for me.

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

Contact Me | Kuroyume's DevelopmentZone


giorgio_2004 posted Thu, 12 April 2007 at 6:23 AM

Never understood exactly how Poser manage the image used as a light probe.

  1. Is the center of the image positioned on the TOP of the "sphere" used for calculating the light? But usually the probes I have seen are taken horizontally... for example the one shown in the second post has a wall and a desktop in its center, not a ceiling. Then what?

  2. Directly related: I have read in some tutorials (i.e. "Practical Poser 7", page 69, point 6) that in the case of an IBL, the position of the light indicator is not important. That seems to indicate that the position of the "dome" is fixed. But if I move the indicator around the scene, the preview light DOES change. Is this only a preview matter (meaning that actually in the final render the results are indipendent from the indicator position) or moving the indicator actually turns the "dome", or the "sphere", or what-is-its-name?

Giorgio

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FrankT posted Thu, 12 April 2007 at 6:51 AM

in the few tests I've done, moving the indicator just affects the preview, the render looks the same whereever the indicator is

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AntoniaTiger posted Thu, 12 April 2007 at 7:15 AM

I was watching Doctor Who Confidential on Saturday, and the effects people seemed to be recording lightprobe images. Just holding large reflective balls in front of the camera. Look carefully at the images which come with Poser, and you can sometimes see the phorographer dead-centre. Such simple lightprobes will have a gap in the coverage mayching the area of the scene hidden by the sphere, so if you were creating one in Poser I suppose you'd want to get the tight framing by adjusting the camera focal length, rather than moving the camera closer. That sort of fake lightprobe might be useful, but you need a full 360-degree set. And that's what it's supposed to replace. I've seen a description of a low-res lightprobe, using roughly-blocked light and shade.


pjanak posted Fri, 13 April 2007 at 6:19 AM

**kuroyume0161,**I've only recently read up a tiny bit on HDRI. But I have gathered that its a combimation of multiple exposures. I was going to "fake it" inside Poser. I guess I do sort of use IBL and HDRI interchangabley. I don't mean to though. I would have started last night. But I got stuck on a double at work. I'm just getting home now and I've got to be back at 2pm so I gotta go sleep in a second. I really hate that. Pretty much no "me" time. Hopefully I'll have a result to post in this thread eventually. Yes I too favor a 3D representation thar can be manipulated. Over all I like but I hate Poser. If you can figure that one out. And all these years of version after version I would have thought we'd see thin gs like light cones and fall off ranges and such. But no.
Pete