Photomatching 3D CAD model to old photos for furniture reproduction - a method

It occurred to me that my method for recreating old furniture and so on in 3D CAD by photomatching might be of interest to others. I've been doing this for years.

The screenshots below show my method, applied here to reproducing a chair made in 1923, attributed to Ernest Gimson as designer and Peter Waals as maker. The CAD modelling process relies on using a transparent image overlayer on top of the CAD program. In my case, I'm using Rhino 3D for the CAD modelling (but it could be SketchUp or whatever), and Image Overlay Utility as the transparent overlay. On this chair project, I've pretty much finished the photomatching now, but still have to detail the model.

Both SketchUp and Rhino have photomatching commands that assist you to find vanishing points in the photographic perspective. That can work, if you have the entire original photo, that has not been cropped. But often photos found in books and on the net have been cropped; and they all have unknown focal length, and then these photogrammetric aids don't work well. Old studio photos sometimes used sophisticated bellows cameras that could intentionally mess with the perspective too. Really old photos had lenses with uneven optical properties. Over the years I've tried and encountered all of this. I have found it is often just a lot easier to use a transparent overlay, where you project your old photo on top of the CAD viewport, and line up the cad model to match it. You need to get the zoom right, and adjust the viewpoint to match the photo. In Rhino you can adjust the focal length too, to try and match that of the photo.

In the images below, I had two photos of the same chair - one from a book, one from the net. Having two photos really increases the confidence level. The thing is, no technique gives a perfect result. But with the overlay technique, you can focus on one area of the object and get the relative proportions right, and then you might have to reposition to work on another area. That's because foreshortening effects and so on are quite hard to perfectly mimic. Ultimately, you have to use some judgement and interpretation. But you can get very close, especially if you know or can deduce a few measurements of the original object.

Anyhow, I'm going to leave it there. There's a lot more to say, but anyone inspired by this technique can probably figure it out for themselves from here.


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1. Matching up to a photo of the chair from the net. I adjust the transparency slider up and down repeatedly to see more of the photo or more of my model, while I focus on some particular detail. On this model, I've adjusted the size, shape, and position of every piece of wood in the model at least twice, gradually settling on a design that closely mimics the original. Why bother? Because I admire this chair a lot, and Cotswold A&C generally.

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2. The model matches up ok with the book photo too, a useful double-check, but as usual I can get a close but never exact match. I am satisfied that I am very close though. Here I've been concentrating on the back, and so you can see that here, that's lined up well, but as a result the leg feet are misaligned. But I know the overall height, the seat height and the front width, so the misalignment is not actually as much of a problem as you'd think. I'm not concerned about the overall measurements - as I say, I have those - it's that I need to get the detailed elements correct relative to each other (tapers, angles, widths of pieces, that sort of thing). And this method does that well.

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3. I'm reasonably happy with the outcome. Now that I have the overall shape, I'll have to refine and detail the model, and also use it to 3D-model the router jigs I'll need.

A last word: There are free apps available for transparent image overlay. The website alternativeto.net has a list of them. I have tried a few of these apps, and settled on "Image Overlay Utility" by Geordan Keller. His website says that he is having trouble with virus checkers detecting the exe file as malware. IOU isn't malware, but I find I have to add the folder that contains IOU to my virus checker's exclusion list or else it 'quarantines' the exe file. IOU has a free version and a paid version (the paid version saves your setups, but otherwise the free version is the same and works fine).

- Ian -

thanks for this

when designing from a photo I use an orthographic drawing package (CorelDraw) rather than CAD. Corel is based, in part, on using layers which allows a photo to sit behind the drawing. (When I need a 3-D rendering I'll replicate the design in Sketchup.)

The other piece of software I use on occasion is PTLens -- this software can correct for lens distortion, vignetting and perspective

I use CorelDraw too, which is a 2D drawing package, but I don't use it for this purpose. The reason being, that rather than simply tracing a photo in 2D, the aim here is to make a 3D model. That 3D model can be rotated and zoomed in the 3D CAD package display until it corresponds to the photo. When the photo and the 3D model match, you have replicated the object in the photo. In getting to that point, you necessarily have to size and shape the parts of the model until they are pretty much the same as the original. So you end up with more than a tracing of a photo - you end up with all the dimensions that you need to build a replica.

But of course, this is only one way of working. In the past, people would rule off vanishing points from a photo stuck down onto a large sheet of paper, using perspective drawing techniques in reverse. I remember doing that as a kid, to make historical buildings for my model railway (I made the model buildings but the railway never materialised). Before 3D CAD was widely available, I used much the same technique with CorelDraw. Then SketchUp arrived and I used its perspective tracing tools. And then I got Rhino and used its perspective tracing tools. I also looked at feasibility of photogrammetry software. But in my experience I have found the technique I use here to work much better than perspective tracing, when dealing with old and/or cropped images. But we all do what we find most suited to our skills, time and tools.

- Ian -