Export a model from Poser to Maya using to .obj format and he seems to import very, very small. This is because Poser uses something called Poser Native Units.
According to Poser's documentation, a Poser Native Unit, or PNU, is 8.6 feet.
This means that a 6'6" man would be 6.5 / 8.6 = 0.756 PNU's tall. (six feet six inches = 6 point five feet)
When Maya imports the man, Maya doesn't know about PNU's. Maya just sees that the man is 0.756 units tall, so in Maya, which I have set to centimeters, the man comes in smaller than a sugar cube.
To match DAZ Studio to Maya, set Maya's film back to 1 inch and work in centimeters in DAZ Studio
To test how to match a poser lens to a Maya lens, I modeled a 0.6 by 0.8 by 0.1 unit squashed unit cube in Maya.
I turned off any options that might scale or translate my .obj format Maya object on import into Poser.
I made a new dolly camera in Poser and set its lens to 50mm. I decided 50mm was the lens I wanted to match.
Then I positioned Dolly Camera 1 until the 0.6 by 0.8 unit rectangle visually filled the 600 by 800 pixel window.
For some reason the main camera provided by Poser was no good for this work. Setting its dolly-z to 0.0 didn't actually place it at 0.0 on the z-axis. Poser seems to have its own odd ways of doing things.
I set a Maya camera to the same position as the Poser camera. I also set the Maya camera's focal length to 50mm, the same as the Poser camera. But the match didn't 'click' until I set the Maya horizontal film aperture to 1.0
So a Poser 'film back' or 'chip sensor size' is equivalent to a Maya aperture 1.0 inches in width. I'm not sure what format that might be emulating. I guess Poser uses 1.0 to keep the arithmetic simple.
One last problem... Matching a Nikon D200...
If someone gives you a vertical aspect shot (which I do more often than horizontal), a Poser lens and measurements - lets say it's a 50mm lens - then I set the Maya film back to 0.622 by 0.929 for reasons described here, by I adjust the focal length by eye (no trigonometry) until it matches. (close enough). For a 50mm poser lens I get 31.25mm Nikon D200 lens. Interesting to note: 50 / 31.25 = 1.6, the zoom factor for a DX lens.
Now lets go the other way...
It's more likely that I'll shoot something with a 50mm on my Nikon D200.
To match that in Maya, set all distances the same, set the lens to 50mm and set the film aperture to the DX chip size, 0622 by 0.929 (for a vertical 'portrait' aspect shot)
To match in Poser, make a new dolly camera, set the display to PNU's, 'poser native units,' set all distances the same, the poser film aperture seems to be out of user control, but it defaults to 1.0, finally set the Poser lens to 80mm which is 50mm * 1.6
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UPDATE 4/5/09 - Based on comment feedback
Here is an animated GIF based on the preceding post. The Poser numbers for camera position are PNU's. The Maya numbers are the same numbers, only Maya happens to be set to centimeters. Both Poser and Maya cameras are set to 25mm, but the Maya horizontal film aperture has been set to 1 inch.
Click on the thumbnail above to get a close look at the high resolution Poser screen grab.
Click on the thumbnail above to get a close look at the high resolution Poser screen grab.
1) The model size has NOTHING to do with matching the camera settings. You should check and seee if someone has created a Maya plug-in that will expand and reduce the OBJ for import and export. This is a matter of modeling and rendering CONVENIENCE for your 3d software. I know such plug-ins exist for C4D and 3DS, and would be surprised if there isn't one for POSER-MAYA/MAYA-POSER. The most critical thing to know about model size with Poser has nothing to do with the camera - it has to do with making certain you match scale and location for the creation of morph target objects. A well-written I-E plug guarantees that.
2) You can vary your camera settings in Poser. For example, the default MAIN camera setting is focal 75 and focal distance 17.2 - and there are adjustment inputs for these. You should be able to match these with both your real life and Maya cameras. If you change your Poser camera, just remember to adjust your others. Or, if you have a bg pic taken with a RL camera, remember to adjust your Poser and Maya cameras to match. On the other hand, if you're gonna export to Maya for rendering, who cares what the Poser camera setting is? At that point, having a matching Poser setting simply gives you a better preview sense before you export and re-render the models in your 3d software.
If you don't know the size of the object in the units Maya uses, you can't position the camera the right height and distance from the subject to match the Poser framing.
Focal length alone does not tell you the whole story about how something will be framed. Try a 50mm lens on a Nikon D200 with its DX-sized chip. Now try the same lens on a Nikon D700. The angle of view will be much wider because the D700 is a full frame camera. A conversation about lens focal lengths doesn't mean much without a precise understanding of what format those lenses are projecting onto - Medium format? VistaVision? IMAX? A tiny point-and-shoot chip? A lens with a wide angle in one format may produce a narrow angle of view in another format. You have to know.
What is the film back size in Poser? Do you know? Is it published anywhere? It turns out to be 1 inch, from what I've found - so to match a Maya camera to a Poser camera to need to match everything, including position, orientation and focal length, and THEN you need to set the Maya film aperture width away from its default to 1.0
Finally - I need great accuracy between my photography, Poser, Maya and Maxwell. Why? I pose in Poser very precisely to a reference photo which I then further render in Maxwell via Maya.
Here is why...
http://www.digitalartform.com/archives/2009/03/nothing_is_real.html#more
Sorry. One more thing regarding scales. Every piece of 3d software has it's own scales...and they are all ARBITRARY. The folks who designed Poser decided what size a PNU should be, and most of their subsequent 3D models conform to that size.
On the other hand. many DAZ and other 3rd party models for Poser, don't match the PNU...most notably Vicki's 1, 2 and 3 from DAZ. And there are 3rd party prop models that have been released at all kinds of varying sizes.
What's important to remember is that there are NO RELATIONSHIPS between the scales in different software. A model executed to be 1 meter tall in C4D will not import to 1 meter in Maya, or Bryce, or Poser. All measurements/scales are internal to the software. The only thing that's absolutely known about scale is that Poser models, when exported to OBJ. format, come out incredibly tiny when imported to most other software. In C4D, for example, the import-export plug expands and contracts the model by no less than 1000...just to get the model to an easily workable/renderable format. Judging by your pictures above, a Maya-Poser conversion might be successful at a scale change of plus and minus 10.
Again, the key here is that all of this is arbitrary to the individual 3d software. There are no scaling "standards" as such for .OBJ format models or for any other format that I know of.
Do exactly what I describe in this post and your Poser and Maya images will match.
If an object measures 3 PNU's in Poser 7 it will measure 3 centimeters in Maya if Maya is set to centimeters. The conversion is 1-to-1 ... just like that.
I am suggesting, among other things, that Poser isn't anywhere near as complex nor flexible as Maya (or C4D, for that matter). If you want to MATCH THE POSER CAMERA, I believe you will find that the angle of view and focal length numbers are all that you need. Making POSER MATCH AN RL CAMERA, with all its variants, is another trick altogether...as you seem to well understand. Sorry, your piece was unclear as to which conversion was your need.
However, the matter of scale interests me since your final render seems to be intended for Maxwell. So, again, aside from previews, why bother about cameras and scaling in Poser - unless, are compositing a Poser render at the same time?
I want to put real people into Maxwell backgrounds, and I want their invisible CG twins to cast shadows in Maxwell and reflect in shiny Maxwell surfaces.
I want to line up the pose as best as I can in Poser because I am too lazy to rig a Maya character if Poser characters are good enough for shadow casting and for (certain kinds of blurry) reflections.
And typically in my process the photo comes first. The poser model comes next. The background comes last.
"If you want to MATCH THE POSER CAMERA, I believe you will find that the angle of view and focal length numbers are all that you need."
Where in Poser is the 'angle of view' of a camera specified?
Thank you. So much of what you need makes much more sense now. However, while this particular focal length, aspect ratio, et al are effective for this particular project...I would suggest that everything would need adjustment if you did something as slight as altering the focal length. I.e., your formula, while working just fine for this picture, is also arbitrary.
Not to beat a dead horse, but if you scaled the model twice as large you could still work out a formula that would satisfy your lighting and rendering needs. I bet if you changed your software preferences from metric to British, you might find that centimeters suddenly had a 1-to-1 correlation with inches...or feet. Suddenly 3 inches to 1 PNU, or 3 feet to 1 PNU, would work peachy. The 3 centimeter measurement in Maya is just as phony as the 8.6 foot PNU in Poser. In fact, to be clear, you should specify clearly which preferred Maya measurement you are using.
And while this relationship may work for this particular shot, the numbers would become meaningless, for example, in a wide-angled landscape. There, one of the blessings of 3D, is that you can scale down the model size to conveniently fit your standard creation and modeling screen. And you would still be able to render a perfectly fine picture...at whatever aspect ratio and lens settings and film specifications you have mind. The fault in your tutorial, as it is now written, is that if I have a seventy-story building that I want to shoot that 1) it has to be seventy stories in relation to the PNU in Poser, and 2)I then have to use a ridiculously large model to achieve your ends as you describe them for Maya and Maxwell. That's simply not so.
In fact, I don't believe you intend to say that - but it is the final logic of this crud about comparing arbitrary measurement units from one piece of software to another. I believe you understand that these measurements are meaningless in any sense other than you have found a working relationship for one particular setting and picture. Your settings are ABSOLUTELY CORRECT...for that picture at that distance and that scale for your needs. The formula you suggest may not have much applicability to anything else.
You are right. If I do exactly as you say, it will work. But if I need a portrait with standard 80 x 24 focal settings and decide to use, for whatever reason, a wide screen presentation (say for a horizontal poster) and I want to be closer or further from the subject..none of what you've specified will work.
I will stress again - for many others who are looking to composite photographs and renders, and particularly to those new to the processes and, therefore, more easily confused - for most work, matching the aspect ratio, the focal length, and the focal distance from Poser to the 3D software they are using should be just fine. If adding in a RL photo, the other issues you have raised are important but may usually be bypassed by employing basic lenses and simpler camera settings. For example, I can't imagine two final pictures where minor variations in film backs make a substantial artistic difference. One doesn't have to choose to work with the variety of SUPER lenses available now, for example. In fact, since Poser doesn't allow for such variations by default...it might be suggested that using simpler camera settings and judiciously editing the render in post might produce comparable results. Most of the time, in art, 'A' needs to look like 'A' but doesn't necessarily have to emulate 'A.' Art is often more effective in suggestion than specifics. And there is a real logic to simplifying one's work flow.
Please, this is not to say you are wrong by any means. I do, very much, admire your tenacity. Most other 3D and commercial artists would be happy to add their shadows and reflections in post. Where there is a need, I tend to like exactitude myself.
For what it's worth, you put this site up on Twitter to get a response and, I assume provoke conversation. We are having a good one...don't suddenly get the willies and stop posting my responses. This is the kind of back-and-forth that helps others learn...and most 3D sites would kill for this kind of discussion. It might be ok if both of us were 75% right in our particular perspectives...sometimes people learn more when they see the differences that choices allow.
Jeez, if I were lucky enough to have a site like this, I'd pray for a devil's advocate. Everything would get better because of it...
If I stop it's because it's 2am, but I'll post everything in the morning.
I'm not always right. Here are two posts where the comments probably have better answers than my original post, and they've been up for years.
http://www.digitalartform.com/archives/2005/10/compositing_pre.html
http://www.digitalartform.com/archives/2004/10/colorize_black.html
I believe you will find that the FOCAL DISTANCE number in Poser translates to the ANGLE OF VIEW setting. There may be no logic in the assignment of terms, but logic has never been Poser's strong point, lol.
Fun to read the previous Adobe tuts - I have taught myself so much of that stuff over the last years...but it's nice to see there's someplace that others can get a jump start. I do understand exactly what you're doing...your generating reflectances and shadows (and I would hope color and spec, et al) for the additional 3D pieces you decide to add to your photograph.
Not knowing the final intended scale and destination for your work, it's hard for me to judge whether this adds substantially to your final composition or whether post-generated adds(artwork vs. renders) would suffice. But no matter what I think, it's your preference to go for the result that way...and I have been known to go to some really ridiculous lengths to see what I could out of the renderer versus what could be done in post. Therefore, I am the last person to say that what you are doing may be unnecessary, lol.
The only question I have at this point is, why can't you simplify your RL camera settings, and then do some judicious postwork re aspect and scale to make the recreation of such effects faster and more effortless?
For what it's worth, I tend to do lots of software-to-software work, Poser to C4D and tend to use minimal RL camera stuff. I work in reverse. My "human" models ARE 3D models. It's rare for me to use a Poser render, but not unknown...I render primarily in C4D. I enjoy the 3D modeling side of the work and, unfortunately, don't create as many clothes as I should be. I like the challenge of "selling" the 3D model in final result.
BTW, I didn't know that Maxwell was available for C4D until our discussion here, and I checked out the site. Unfortunately, I have ver9 and Maxwell starts for C4D ver10...and I just don't have an extra $3000 lying around anywhere, lol.
I updated the post with a quick Poser-Maya match.
There is an animated gif and two high resolution screen grabs.
Indeed. I went searching for a POSER-MAYA importer-exporter last night and was disappointed in what I found. I can only guess that most people who use Maya would create their own figures there and, therefore, have litle use of Poser figures. On the other hand, I think your use of the Poser figures as dummies for subjects in a real photograph is a novel and interesting use of them.