" For animation, I think it's quite simple : with 10 identical PCs, it would be about 10 times faster than with one PC :)" I doubt it. I think your figures reflect the true nature of distributed rendering efficienty. I've had a deal of experience working with mental ray on farms of up to 1500 nodes. In the early days we looked at distributed rendering - which is what Vue/Rendercow does. The ratio of rendertime to number of machines is never linear when you're rendering in this way. hard truth, this kind of rendering is nowhere near as efficient as rendering one complete frame per machine. If you start scaling this up to movie size then the fun really starts. I'd be willing to bet once you get up into the hundreds of CPUs the time per frame will actually drop below the time it takes to render one frame on a single machine. Rendercow rendering is attractive but it's not effiicient.

"Does it really matter if the math is that of true lenses? Is not the purpose of Vue to simulate reality, rather than to recreate it? In other words, if it looks enough like photographic lenses is that not sufficient, no matter the method? I haven't explored the Vue perspective/aspect ratio render stuff though". hehe. Remember, under the hood, Vue is doing exactly the same as any other 3D app. View transform is pretty standard and there's only one way to transform 3D into 2D (unless you're using After Effects and god only knows what's going on there). So, it's doing it right, it's just being a bit selective about what it exposes to you. Does it matter? Depends. For most users probably not. But if you want to match to live action or another app then yes, it does because you're probably going to be dealing with FOV, not focal length. For example, my XSI camera I'm using a 34mm focal length but I'm using PAL as the image format. If I decide to work in another format then I need to adjust my focal lenght accordingly. Note, this isn't a limitation of XSI, this is the way real world lenses work, so it's not behaving like real world cameras at all. I'm being picky right now because I do have to match XSI moves back into Vue. I'm also working with kind of an odd aspect ration; 4.4:1, so I'm going to be a bit touchy until I know it works. If it doesn't, expect me to come back and scream a bit more ;-) For most people using this software, it's not an issue but that's not really my point I was trying to make. What I was trying to say is, it's wrong and in my experience, you don't do it properly it comes back and bites you in the ass. I come from a background of film and photography and I've done a lot of movie work, matching CG into live action and vice versa. I like to see things done properly and it bothers me when it's not, because that's when things go wrong. sorry for boring everyone. I'll go back to my box now. see www.cg-soup.com for some of the stuff we do.

"Beginners in photography often think of "non-normal" lenses as causing distortion, but they don't. They just take a different sized hunk out of the world than we are used to, at the typical viewing distance of the photo." yes, you're right. Perception of perspective is largely dependant upon viewed distance. The idea of a 'standard' lens is based on a 'normal' viewing distance. the other mistake people often make is that widening or lengthening focal length alters perspective. it doesn't. Moving the camera close or far changes perspective, not changing focal length. http://en.wikipedia.org/wiki/Perspective_distortion_caused_by_lens_focal_length

"Maybe I'm not clear about what you are saying, but surely if 3d software was to add format of the film or sensor size it would limit the render resolution? Maybe film or sensor size could be added as an option, but one of the big advantages of digital software is that there is not a restrictive limit to render size...I would put that as a big plus." you're not understanding either focal length or perspective transforms work. Most GP 3D apps - Maya, Xsi, Houdini - don't work in the quite limited way Vue works and with good reason; focal length is meaningless unless you take into consideration the format you're working with. And it's not a plus at all, it's a pain because it's misleading and just plain wrong. http://en.wikipedia.org/wiki/Angle_of_view : calculation of FOV from Focal length. http://en.wikipedia.org/wiki/Perspective_transform : detailed description of how world to screen transformations work.

well yes, of course that's what it does. What else would it do. But it's all rather arbitrary. And incorrect, to boot. Supposing you needed to match back to a live action shot or some other software? The point here is that the focal length is meaningless without a knowledge of the format of the back plate. For example, a stills 35mm camera, 24mm is wide angle but if you were shooting, say, 4x5 plate, 24mm is extremely wide. Vue is only giving you half the information. Not really enough unless you're just playing.

so what exactly constitutes a standard focal length in Vue. There's no notion of film back size in the software; focal length is pretty meaningless without knowing the format of the film or sensor size you're using.