Is there a method to exactly match 3D perspectives to a photo?

[paulison]

Hi everyone,

Up until now i have been estimating camera position and target point in order to generate images to match photo's. The result is that there is always a degree of innacuracy.

At the moment I have a client who said "there should be an exact science to doing this" and unfortunatly his previous 3D illustrator told him that it was possible to do it 'exactly' and now he insists that this be done.

I remember hearing about a certification process in the UK where councils would be assured that the artists impression they are shown is correct. This job is quite a big building and although this council doesnt reqiure it, I am trying to find information on this process.

My guess is that surveying equipment is require in order to get the exact target point of the camera then the photo is taken. This may be the single biggest unknown veriable that is typically guessed when camera matching

I generally resort to perspective adjustment in photoshop in order to make perspective lines meet up but this doesnt give accurate results and something else always gets skewed in the process.

Any help is much appreciated. Should this be in off topic?. i thought it may be relevant for working with the vray physical camera.

[tct70]

Hi,

When I do an image for compositing into a photo, I get the camera position and target added to the survey drawing where possible. Also make a note of the camera settings (lense etc) so you can match them in max.

Finally, I ude the daylight system to ensure my sun is in the correct location to match the time of day the photo was taken.

Hope this helps.

[suurland]

If you have several photos from the same location you can track it in syntheyes or what ever racking software you have.

If you have only 1 photo you need some more info, if you have measurement of the objects in the scene you can use max's own tracker and get a accurate tracking that way. Build a simple model using the meassurement in 3d and use corner of buildings or whatever to add your campoints to.

/Thomas

[instinct]

Well there's Camera Match in Max. Works fine when you take measurements with care and have enough (more the 6 if i recall) reference Points.

Regards,
Thorsten

[Preisler]

Hi,

Tim Jones made a dvd where he show the process of setting up a camera from a reference photo.

http://www.thegnomonworkshop.com/dvds/tjo01.html

Preisler

[DrJan]

This tutorial has helped me alot with figuring out how to do Camera Matching and gave me good results. As long as you add enough camera reference points and know the estimated (or exact) size of neighbouring buildings, this should get you pretty far...

[jujubee]

Well - you can almost guarantee that the photo taken is perpendicular to the camera - so match the camera 90 degrees to the photo.

Then its a matter of either rotating the rest of your scene or the camera + Photo Plane. Usually I use a point of reference (such as a street curb) to help align the photo and the geometry.

[Paul Oblomov]

Very accurate solution. Of course, if you know measurements and have lots of photos from diff angles.
http://imagemodeler.realviz.com/phot...g-software.php

[joconnell]

I'd normally try and match a plane to get the lines of perspective to match up by adjusting the camera fov - then I match a box to a corner of a building by moving its pivot to its corner, align the box corner to the building corner and rotate it until it matches up (it'll normally be aligned arese ways at this point) then lastly parent the camera to the box, rotate the box back to 0,0,0 so it's lines are parallel to the ground and wall (which will ajudt the camera pos and roation) then unlink the camera.

Alternatively use syntheyes which has a reall nice camera matcher built in.

[MikeHampton]

Well, as stated above, the camera matching utility in max works pretty well. BUT you have to know at least six points in the photo that are not all coplaner and how they relate to one another (dimensions in all three axises). If you can see a corner of a building that is at 90 degrees, that is usually a good start. Although I have been able to get camera matches by using cars and other things in the scene. The more info you know for sure.. the more exact you can get the camera match, because if you know nothing.. you have to estimate the sizes of things. The quality of your camera match is going to be based upon how well you guess the sizes of things.

So unless you placed markers in the scene (and measured how they relate to each other) or actually go and measure known points in the scene when the photo was taken.. it's probably never going to be 100%. But often you can get pretty close.

Look in the max help, or do a search for an online tutorial. Although it's not that difficult, it's a little to in depth for me to try to describe how to do it here.


Also note that you have to have an image that the perspective hasn't been altered in any way. If it's been photoshoped in any way to alter the perspective.. you aren't going to be able to get a good camera match (if at all).

[bernhard]

maybe this one..

maybe my old tut using icarus will help you a littel bit too..

http://www.bernhardrieder.com/cgstud...struction.html

bernhard

[Clifton Santiago]

@ paulison:

The process you are referring to is called verified views. It involves hiring a professional photographer who knows the VVM (verified view methodology), and has at least a professional architectural shift lens, or better, a medium or large format camera. The photos are taken from the desired vantage points, and their position in marked. You then mark about 25 survey points on each of the photos (corners of buildings, and other stationary objects). The surveyor then surveys those points from each vantage point, as well as the camera position, all in OS coordinates. Then you get your OS cad site, re-zero the origin to the nearest OS grid intersection, adjust all the survey data accordingly, and plot all the survey and camera points. Match the sun to the time and date the photos were taken, create a camera at the surveyed camera location, and adjust until all the survey points line up with the background image. You should only be adjusting the HFOV and the target point. Once everything lines up (or close, with 35mm camera, there will be more distortion... I usually make sure the points near the top of the building line up most closely), drop in your architectural model, and you are ready to render a verified view.

[paulison]

excellent, thanks everyone. That its a pretty comprehensive list of methods and tools to use for camera matching.

I think that my problem in this case is lack of reference points so i'm going to let the client know that for this job, its going to have to be a best guess unless we retake the photo's and measure some distances/reference points. They wont be happy though since they have already paid a professional photographer to do this.

There is some really good information in this thread and i'm going to try out the various methods so i know how to do this properly. thanks again!

[Giovanni]

Paulisoin,
there is also a less scientific way, but still can give you a pretty accurate result, and is fast to use.
Get Sketchup v.6.
It has a built in photo match feature which is alone worth the 500 bucks for the professional version.
It is a 3D comp dream come true. You only need one photo, but cannot be corrected, you need a normally distorted photo (vertical lines not forced to be parallel).
Sketchup shows you 2 couples of segments which you can drag and move to match the perspective on the photo. Also you can adjust the location of your origin and the overall scale of the model compared to the photo.
It is a pleasure to use, althought you do need a photo that shows enough reference geometry for you to guess the perspective.

After you got the perspective matched, you save your page, that is a Sketchup camera, and export your model as 3DS. It will come in MAX with the camera. You need to match the output resolution to the photograph you used...

Regards

gio

[gagui]

Bernhard where can i find icarus software for download?