The correction system I first suggested does not really apply here ... it's more used in architecture.
Fact is no correction of an image will create pixels missing due to fore-shortening ... it simply elongates the area. The Distortion we're seeing on this image is due to the "camera" being used at wide angle ... probably about 28mm focal length 35mm film equivalent ... or even less, maybe 17mm or so. However there would be very little foreshortening since the camera is perpendicular to the viewing plane of the cycle ... there is curvature from the extra wide angle used. To determine what is going on perhaps model both wheels with guessed rim configurations and render that, in perspective, with an effective 28mm lens setting and see whether the distortion matches. You would then have data for real dimensioning from this draft model. Personally I would ignore the distortion and call the image flat absolute and re-model from there ... the difference would not upset me. If I still felt doubtful I would guess a small addition at each edge of the overall length. Another clue in your image is the knowledge that the wheels are perfect circles ... draw a perfect circle over the image at wheel size (probably do this in a vector programme with the bitmap imported) ... if the foreshortening is significant it will show and it would be simple enought to stretch the image until the wheels were perfect circles as they must be in ortho. At adjusted stretch the true length of the bike will be almost but not entirely correct. Use that distortion factor of top views as well but only in the same axis of course. And if this was done in a vector programme then all the data you need would most likely be very readily available. Or something. To determine absolute dimensions some known dimension has to come into play. Perhaps there is an image with a human figure of average height to work from, perhaps assume Harley wheel and frame sizes and go from there. That's all I can immediately think of. Hope it adds to the fun Neil Cooke ----- Original Message ----- From: "Matthew Hagerty" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, July 19, 2006 1:04 PM Subject: Re: Compensating for perspective > Here is a link to the reference image I'm using: > > http://digitalstratum.com/images/tron/lightcycle_all_sides.jpg > > Note the front wheel. On the right you see some blue between the black > inner part of the wheel and the edge (I call this the rim), which is > missing by the time you get to the left side of the wheel due to the > perspective. Also, the center point of the rear wheel is actually in > line with the rear of the body, but it looks slightly set-in. The > bottom view also shows what looks like the rear wheel intersects the > body and does not fit in the wheel-well, but that's not really the case, > it does fit. > > It is these kinds of errors that makes it particularly difficult to > determine several things: > > 1. Overall length of the lightcycle. > 2. The true curvature of the canopy. > 3. The size and placement of objects. > > I was hoping there would be some way I can adjust for the perspective as > I move away from the center (where ever that happens to be...) I think > the perspective is worse from side-to-side than top-to-bottom, but it's > hard to tell. > > Matthew > > Neil Cooke wrote: > > 2D images can be reworked in Photopaint/shop to have no perspective showing > > in the verticals and with some images it is possible to go some way to also > > remove this in one horizontal direction. Maybe post us one of these problem > > images? > > > > To remove perspective in all aspects of a comprehensive 2D picture ... it's > > probably best to start again and remodel in RS ... or live with it. Maybe > > minimise it with (non) lighting, blur it, etc. > > > > Neil Cooke > > > > ----- Original Message ----- > > From: "Matthew Hagerty" <[EMAIL PROTECTED]> > > To: <[email protected]> > > Sent: Wednesday, July 19, 2006 11:54 AM > > Subject: Compensating for perspective > > > > > > > >> I have an image I'm using as a reference to accurately reproduce a model > >> from (yes, still the lightcycle, but I'm very much an absolute > >> perfectionist.) The problem is that every known image was rendered with > >> perspective, which may have been the only option in 1982. When trying > >> to size objects and place them properly, the perspective causes an error > >> which makes it difficult to get things like the curves and angles > >> correct. Is there any way to compensate for the perspective in the > >> original 2D image? > >> > >> Thanks, > >> Matthew > >> > > > > >
