Skydomes are great.  With the correct shaders you can get superb results, right.

Er, well not really.  With all the will in the world, a dome cannot reproduce the dramatic perspective you can see from a real sky.  The only way I can imagine you could do something similar would be to make a dome 12000 miles radius (scaled to Poser, of course).  Not really practical, huh?  Even then, you'd lose a lot because there would only be a single layer.  So, you tack on lots more layers, each with a degree of transparency.  Oh, the agonizing hit in render times.

The alternative is to use something like Rubicon Digital's SkyGen.  It's a lovely product but with some caveats.  It uses the Poser background as a shader, so unless you're prepared to save as a JPG, the background is lost.  The lack of all round coverage also means it's of limited use for reflections, too.  Great for comping but not so good if you like to get the reflections right.  Even a dome with a similar set of colours wouldn't get the necessary accuracy.

Now to my question...

Is there anything out there which can do the full coverage of a dome, combined with the dramatic perspective effects available from SkyGen?  Is it something practical for me to make?

Any ideas/opinions/tricks/tips or advice welcomed.

 Well.. IMO the RDNA TerraDome is great. I use it whenever I need to do outside renders these days. The great thing is, it comes with suitalbe lights and all. And the sky is textured in a way so that it - IMO - looks right.

My free Environment Sphere has a diameter of 1500 feet. Yet this clearly looks much grander than that. What am I missing?

like Trekkie, I've not had any issues with a lack of dramatic perspective in things like TerraDome. There may be better things out there, but at least now I have something that allows me to utilize some of these large building models that I've had for years... :D

As Bill pointed out some time ago, your camera focal length needs to be set fairly low: 35mm seems to produce reasonable results. And having a good quality equirectangular image helps as well.

Rightio.  But suppose I want to set my focal length to something close to the human eye, 100mm, for example?

I'll have to take some photos out of my window when there are some interesting clouds, just to show you what I mean.  I know, a picture is worth a thousand words and all that. 

Quote - Rightio.  But suppose I want to set my focal length to something close to the human eye, 100mm, for example?

I'll have to take some photos out of my window when there are some interesting clouds, just to show you what I mean.  I know, a picture is worth a thousand words and all that. 

The human eye is 50 mm. And Poser's focal length is wrong by a factor of 1.4. To accomplish a human eye type of field of view, you want 50 / 1.4 = 35 HAHAHAH.

My render above was done at 15mm. With the 1.4x factor (actually it is the square root of 2, or 1.4142), that's the equivalent of a 21 mm lens on a standard full-frame SLR. Landscape photographers generally use wide angle, 20 mm to 24 mm, for pleasing grand landscape images. That's why I used that value.

This is Poser 100 mm. (141 mm SLR equivalent)

Poser 10 mm (14 mm equiv.)

14 mm (ultra wide angle) prime lenses are highly prized by landscape photographers. If you want to do like them, use 10mm in Poser.

Quote - The only way I can imagine you could do something similar would be to make a dome 12000 miles radius

Aha. I pondered what you could possibly mean by this. It finally dawned on me that you're making an incorrect assumption.

You believe that you'll see more of a larger sphere. This is simply untrue.

In general, as objects move away from you, you see more. But when you make an environment sphere or dome larger, it isn't simply moving away from you. It's also getting bigger!

When something becomes bigger, you see less of it, unless you move it farther away, right?

And the curious thing about pictures in a giant sphere is this. As they move farther away, they also get bigger, and the two effects exactly cancel each other out. A picture mounted to a sphere (or any other shape) that moves away in exact proportion to its size does not change its apparent size at all.

When you're at the center of a very large sphere, making it still larger changes nothing about how it looks.

So - the only thing the makes you able to see more clouds or more sky is to make the field of view wider. That's entirely controlled by the camera focal length, as demonstrated above.

The only advantages of making a sphere bigger are that your camera fits into it easier, less chance that your camera will be outside the sphere when you render, and also more room to move things. For example, if you are animating an F16 fighter jet, five seconds of animation means that the fighter jet will have flown out of a skydome that is 1500 feet in diameter.

And what about a half sky-dome or quarter half-dome? or a plane...?
To extend the rotation angle make rotate the dome with the camera. To make more natural and not always the same sky image, rotate the dome slower than the camera. It will not give 360 degrees, but can achieve a good angle with normal textures.

Quote - With all the will in the world, a dome cannot reproduce the dramatic perspective you can see from a real sky.

The problem is that human eye is not a camera!
All rendering engines use the camera model, a photograph can be very nice but is not what your eye sees.
The camera model is wrong! We need a human eye model.

 Interesting. So Poser's focal is off? This is new to me. It means that all the years I've been using 50 mm I've actually been using.. what? 70 mm or something? This explains a lot :D Thanks, BB!

Fir focal length can make or break a picture. And Poser's default looks mostly wrong IMO.

Fantastic advice, folks.  Particularly BB.  

BB,
  i wish I was part of your family so I could inherit some of your amazing intelligence.
cheerio
lululee

lululee,

Be careful what you wish for, insanity is also hereditry, and we all know BB is a little crazy... :-)

Helgard,
True enuff, but it is such a valuable form of insanity.
cheerio
lululee

LOL.

Here are two spheres. Which one is closer?

Now which one is closer?

Were you surprised?

Quote - And Poser's focal length is wrong by a factor of 1.4.

Well perhaps, then again perhaps not. Actually focal length by itself says nothing at all about the field of view! Focal length is only meaningful in this respect when it is considered in conjunction with some specific size of image plane, and where the image plane is assumed to be at one focus of the lens (or some other defined point).

A 50mm lens will yield one field of view in a 35mm format camera, but an entirely different field of view on a 4"×5" format camera. Knowing the focal length without knowing the size of the image plane  yields no useful information.

In Poser with a square document window, and the camera scaled to 100%, the field of view at 50mm covers approximately 28.4° from side to side. With 50mm at an aspect ratio of 4:3 the field is approx 28.4°  by 21.5°. These values were determined empirically so may not be exact, but should be close enough for most practical purposes.

les,

Excuse my ignorance, but what do you mean by "practical purposes". How would we actually apply this information in a practical sense?

les,

I understand about the field of view being dependent on focal length and image plane size. As the proud owner of a Nikon D90 and couple thousand dollars worth of lenses, I'm well aware that 50mm on a DX sensor has the equivalent FOV of a 75mm on an FX sensor. The factor is 1.5. For Canon APS-C format, the factor is 1.6.

The FOV you quoted is equivalent to a 70mm lens on a 35mm sensor. Which is why I say one must multiply by 1.4 to understand what apparent FOV you're going to get in terms of the most common interpretation of 50mm being mid-range on an SLR camera. It's going to look like a 70mm lens was used.

So, given that Poser doesn't offer us a second parameter to specify the image "sensor" size (FX, DX, APS-C, Medium Format, etc.) then we have to conclude that the "sensor" size was chosen and fixed by the developers. Further, I assume that they decided what sensor size to emulate not because of randomness or stupidity, but an understanding of what 50mm means to most people.

Now without any documentation, but with the understanding of decades of common standardization around 35 mm SLRs, what would a reasonable person expect is Poser's sensor size? Would it be sensible to assume it is 35 mm, since that is wildly the most common format of camera in use? I think so.

And for sure there are thousands of Poser users who mistakenly believe that is the case. Knowing that thousands of Poser users would have that expectation, I consider it a mistake that the crop factor for Poser is the square root of 2.

It is abundantly clear to me that the intention of the author of this bit of code had planned to make it 35mm. But whoever that was, they made a trivial mistake somewhere and accidentally included a multiplier that is the square root of 2.

I can't imagine that this was intentional. The crop factor of 1.414 compared to a 35mm camera does not correspond with any known camera. FX or "full frame" is 1 (same as 35mm). Nikon DX is 1.5. Canon APS-C is 1.6.

If I'm not right about this being a mistake, then what is your explanation for the square root of 2?

Quote - Excuse my ignorance, but what do you mean by "practical purposes".

By "practical purposes" I mean anything that is likely to be significant when you are composing a scene in Poser.

Quote - How would we actually apply this information in a practical sense?

I'm not saying that you necessarily would want to apply this information. My point was rather that focal length taken on it's own is not helpful, nor meaningful. Angle of view does at least tell you something real about the scene, focal length on its own does not.

Quote - http://www.imdb.com/title/tt0111958/quotes?qt0415353
Father Ted: Now concentrate this time, Dougal. These
[he points to some plastic cows on the table]
Father Ted: are very small; those
[pointing at some cows out of the window]
Father Ted: are far away...

Quote - > Quote - The only way I can imagine you could do something similar would be to make a dome 12000 miles radius

Aha. I pondered what you could possibly mean by this. It finally dawned on me that you're making an incorrect assumption.

You believe that you'll see more of a larger sphere. This is simply untrue.

In general, as objects move away from you, you see more. But when you make an environment sphere or dome larger, it isn't simply moving away from you. It's also getting bigger!

When something becomes bigger, you see less of it, unless you move it farther away, right?

And the curious thing about pictures in a giant sphere is this. As they move farther away, they also get bigger, and the two effects exactly cancel each other out. A picture mounted to a sphere (or any other shape) that moves away in exact proportion to its size does not change its apparent size at all.

When you're at the center of a very large sphere, making it still larger changes nothing about how it looks.

So - the only thing the makes you able to see more clouds or more sky is to make the field of view wider. That's entirely controlled by the camera focal length, as demonstrated above.

Erm, nope.  The larger the dome, the lesser the apparent curvature.  Like the sky.  :)  Anything I put on the surface would (naturally) be larger unless I apply a scaling factor.  

Sam, what do you mean by curvature. In the image I posted with the airplane, in what way does that look like a 1500 foot sphere? It looks like miles and miles of sky and sea.

I totally don't understand what you're referring to by apparent curvature. It's not apparent to anybody what size that sphere is.

Let me put this to you another way. Suppose I render that same image but with the sphere scaled to 50 feet, and also to 5000 feet. What is your prediction about how those images would differ?

I scaled the sphere to different sizes and rendered each, mixed them up, and assembled them into one image. No modification was done to each - I simply copied them. Click for full size.

One of them the sphere was 10 feet in diameter, so the surface is just 5 feet from the camera.

One of them is at the original size of 750 diameter, so the surface is 750 from the camera.

One of them is scaled to a mile in diameter!!

Which is which?

You can get the image I used here:

http://www.flickr.com/photos/simons/2057438156/

Try it yourself.

And let me assure you that this has nothing to do with it being an indoor scene. The same is produced with an outdoor photo. If necessary, I'll render that, too.

In what way is the curvature of the sphere is visible?

http://www.fieldofview.com/flickr/?page=photos/simons/2057438156/

Click and drag the mouse to rotate the camera. Press and hold Ctrl or Shift to change the focal length.

Typo - above I meant to say that one of them is 375 feet from the camera, not 750 feet.

I get your point, BB.  Maybe I am misunderstanding something here but without providing a pic, I can't explain any better.  I'll try to get something to show you what I mean.

Thanks all for your continued input; I'm learning a lot of useful stuff, from it in any case. 

 Well I for one is HAPPY about the camera explanation stuff. Last time I was even remotely into photography was in the early 1980ies (where I did a lot of Macro photos.. those are FUN!) but since Hubby is a total Photo NERD and has been trying to explain to me why the same lens doesn't have the same range on three different Canon D-SLR cameras (two of his and the last one is my oldest Kid's) without me understanding one whit of it... this helps a LOT!

And I'll certainly keep that in mind with future renders. I'd always assumed that 50mm on the Poser camera was 50mm, and thus somewhere between 80 and 1000 would be good for portraits just like IRL...

Thing is.. my math knowledge is, as I've stated far too often,  non-existent. So could someone tell me what I should set the Poser dial to when I want a focal of what I thought was 80? and 100?

For SLR equivalent to 80mm, use 80 / 1.4,which is about 57.

For SLR equivalent to 100mm, use 100 / 1.4, which is about 71.

For SLR equivalent to 150mm, use 150 /1 .4, which is about 107.

 Thanks! I'll try that! Wow it's a BIG difference from what I thought was the correct focal...

Quote -
The problem is that human eye is not a camera!
All rendering engines use the camera model, a photograph can be very nice but is not what your eye sees.
The camera model is wrong! We need a human eye model.

Ermmm...Why???
the physical Camera,lighting& Sky Model is Exactly what we use in Vray
and  Maxwell and Modo401

As far as the human EYE model??
trust me I can not explain to you within the scope of a forum post why such a thing
literally Impossible.

Cheers

Question about the square root, is this in all versions of poser?  If it still exists in the newest ones, someone should be fired over at SM.

All about cameras, but our eye is not a camera.
A simple experiment:
Take Poser, set any focal distance, take the ground plane, set the Camera to look at the ground plane and apply any texture to the ground plane. Next render the scene.
What do you see? At medium distance the texture looks good, at long distance the texture is not so good and in short distance the texture is horrible and distorted.
You can argue that is the texture, well take a huge and with excellent quality texture. When you render it the result is better, but still is bad at short distance.
Now look through your window and at your desktop at the same time. Do you see that the texture of the desktop that if few centimeters fro your eye horrible and distorted? Nooo!
You can argue that is the focal distance, fine. Adjust Poser's camera to a focal distance until the texture at short distance become to look good. What do you see?, well most of the scene had disappeared remaing a big ground and any object that is far away when visible is deformed.
Meantime your eyes continue to see your desktop surface and the far away though your window continue to be normal, nothing disappear and nothing get deformed no matter where you set your focus.

Now the focal length in action. To adjust the focal distance the lens of a camera moves. Between focus on near and far objects the lens moves some millimeters and depending on the camera it can move some centimeters, also for near or far objects you need to adjust the aperture. For very near objects you need special cameras that doesn't work for long distance unless you change the lens.
Well,  beside cartoons, I never noticed the eyes of any person moving front-back, neither changing the eyes for looking at very near or far away objects

At medium distance the texture looks good, at long distance the texture is not so good and in short distance the texture is horrible and distorted.
You can argue that is the texture, well take a huge and with excellent quality texture. When you render it the result is better, but still is bad at short distance.

The problem with photo-based textures is that they are comprised of pixels. This is not the fault of the CG camera.

If you looked at a digital photo very closely with the human eye, quality would still erode.

Quote - BB,
  i wish I was part of your family so I could inherit some of your amazing intelligence.
cheerio
lululee

Not sure if it was inherited: I think it came on him by degrees...

Paloth,

I think you misunderstand. Kawecki is not talking about the texture, he is talking about the fact that the human eye "auto-adjusts", for lack of a better term.

When you focus with your eyes on near and far objects, you are changing the focal length of your eye. When you change the focal length on a camera in Poser, it appears to move forward or backward. That is the effect that kawecki is talking about, that your eyes don't appear to move forward and backward.

Not that any of this matters, but the human eye does not change focal length. It changes the focal plane, providing a choice between near or far objects being in focus.

Prime lenses (by definition, a lens that has a fixed focal length) are similar to the eye. They have the ability to change the focal plane, but not the focal length. The eye does this by squeezing the lens, whereas the camera moves lens elements slightly.

A zoom lens is one that has both a variable focal plane and a variable focal length. Zoom lenses provide the ability to change the field of view, or one might think of it as the magnification.

Human eyes cannot change the magnification or field of view, because they are fixed focal length.

Both human eyes and camera lenses can adjust the aperture - the size of the opening letting light through to the sensor. In the eye this is the iris. In a camera, this is the diaphragm. While the mechanisms differ, the effect is identical.

It is an inescapable fact that any lens-based system cannot focus all things at all distances simultaneously, except when the aperture is a pinhole. This includes the human eye. The focal field of a camera is supposed to be a flat plane, but sometimes is slightly curved, resulting in what is called field curvature. The human retina, being a curved surface, produces a decidedly curved focal field.

The depth of the focal field (range of distances that are in focus) is a function of both the focal length and the aperture. Wider apertures produce a narrower depth of field.

Despite what kawecki seems to be saying, the human eye does not simultaneously keep both near and far things in focus, because it too has a limited depth of field, just like a camera does. In bright light, the aperture is small so the depth of field increases. This means that in bright light you will perceive more objects in focus simultaneously. In dim light, the aperture increases to let in more light, resulting in a narrower depth of field. The same is true with cameras.

In camera lens specifications, we talk about the maximum aperture, which defines the ability to collect light. We talk about how "fast" a lens is. Aperture is given as an f/stop, such as f/2.8 or f/5.6 or f/8. Lower numbers mean more light is collected. Consumer grade zoom lenses are usually no better than f/4 and often limited to f/5.6 at longer focal lengths. Pro-grade zoom lenses go down to f/2.8. Consumer-grade prime lenses, those that don't have to offer variable focal length, can be easily f/2.8, while pro-grade primes go down to f/1.4 (4 times faster). Some really exotic ones go to f/1.2 or even f/1.

The human eye is a prime lens and has a maximum aperture of f/3.5. That's not even as good as my cheapest prime lens, or my pocket camera. The human eye sucks at collecting light.

The limited depth of field at f/3.5 is not particularly narrow but it is noticeable. In bright daylight, when the human eye is around f/16, most everything is in focus, but that is true of cameras as well.

In my camera bag, I have a 50mm f/1.8 prime - very fast, very sharp, very inexpensive. I have an 18-105 zoom with aperture f/3.5-5.6 - nice focal range, but not a great light collector. I also have a 17-50 f/2.8 constant aperture zoom. Not so great range, but a great light collector and I don't have to worry about the aperture changing when I use the zoom. That's my favorite lens and it is far far superior to the human eye.

Having said all that, the camera model in Poser is impossibly awesome at focusing. Everything is in focus no matter the distance. Poser has to do extra work to pretend to be a lens-based camera and produce a narrow depth of field - an option I never use because it is so computationally expensive, and not very effective at mimicing what a camera does.