# Re: Scratchbuilding plans from photos

• posted

Can someone provide me with tips on how to draw HO scale plans based on

> photos of a structure? I have several photos of a yard tower that I would > like to build. I would like to get the measurements as close as possible to > actual by using the photos. > > Any website articles or suggestions would be helpful.

You can use the standard artist's perspective alignment system.

1. find the horizon in the photograph. (preferably on an enlarged photocopy :^) Draw this line in.
2. hopefully your subject will have recognisable vertical and horizontal lines. Check that the vertical lines are vertical to the page and at right angles to the horizon line. If the verticals are not at right angles to the horizon then you have a double correction to make to the scale drawing.
3. Extend the identifiable horizontal lines out to the horizon line. For a rectangular building or piece of rolling stock these lines should intersect the horizon at two points, one to the left and one to the right of the center. If not, then you've almost certainly done or got something wrong.
4. Now pick something that you know the size of. (eg a door) Measure the picture dimension - you now have a ratio prototype/photo. You can measure up the line of the door to calculate the height of the wall. (provided the vertical lines are parallel)
5. Finding a length that recedes towards the horizon is more difficult. An entirely rectangular wall is about the only way to calculate this, but if it doesn't exist, you can construct one on your paper through those extended lines. You will know the front corner height, the door and wall height (near the middle), and the rear corner height. These may well be your perspective construction lines rather than the object itself.
6. If your maths isn't university geometry level then you can divide the length of the wall into rectangles in proportion to the height. (the ratio of height to length has to remain constant for straight lines :-)

If a photograph of (say) a tall building is taken from street foot path level, the vertical lines will converge towards the top. Then you have a more complex mathematical problem!

Regards, Greg.P.

• posted

What I do when I'm working from photos is import the photo into Visio. I set the scale of the page to 1:87 (or whatever scale is appropriate to fit on a page). Then I resize the photo on the page until some known dimensions (like doors) are the right size. Then I place the photo on it's own layer in the drawing and lock that layer, and "trace" the photo, drawing it to make my plans on another layer.

Some of these drawings were done from photos as described above:

jeff

• posted

Many photo programs allow for perspective distortion correction. With photos of flattish surfaces like walls, you can almost avoid having to draw plans at all.

When working with historical structures that no longer exist, and are only minimally photographed, perspective correction saves a lot of work.

• posted

I have Adobe Photoshop Elements 2.0. I found the "Perspective" transformation. But I am not sure what I am supposed to do to get a 2-D wall plan. Can you please provide some specifics on what steps to take? If not specific to Photoshop, then perhaps some general idea of what to change.

As an example, here is a link to an example picture that I mentioned in a previous posting in this thread. Atlanta Terminal station yard (

)

Thanks!!

Scott

• posted

I don't have that program. In Serif Photoplus, I use the distort tool and grab a corner and stretch it, then another corner, and so on until I get both ends of the wall more or less vertical, and all the window casings more or less horizontal. I then eyeball the horizontal/vertical ratio and tweak it. One aspect of that is it is possible to do selective compression for a model, while still retaining the overall look. I'm sure there is a scientific way to insure an accurate rendition, but I'm too lazy to try to figure that out.

The photo you suggested has some extreme distortion, so it didn't peel back as nicely as a photo that was only off by a few degrees. I played with it for ten minutes and ended up with these.

Note that there are visual cues that make the image still seem twisted. The AC supports are still at an angle and the air conditioners are offset. The further away from the plane of the wall, the weirder things get. Lens distortion and curves or projections can also give some odd results.

You can also use a program like the freeware PhotoModeler lite to take a number of photos of the same building and force them into a 3D virtual model. I think you can download it from here:

If not, just do a web search for it. I got my copy a few years back. There is a learning curve, and the process is time consuming, but I suppose it could be worth the effort in some cases.

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