Simon Hartshorne Posted June 19, 2020 Share Posted June 19, 2020 I apologise if this is a FAQ, I can't find it if it is. I am trying to scratch build and I have a decent photo of what I'm building. I'm sure that somewhere I've read of a programme which can scale a photo such that dimensions can be derived from it - or did I dream it.....? Any pointers would be very useful please, thanks in advance. Simon Link to post Share on other sites More sharing options...
decauville1126 Posted June 19, 2020 Share Posted June 19, 2020 If it's a piece of standard gauge rolling stock then the buffer centre height above can be taken as 3ft6in. That's always a good starting point. There is a free programme called Gimp that you can use to manipulate an image to bring it sort of side on. There was an article, way back, in Model Railway News, that showed how to produce elevations of structures from images. Basically a reversal of the procedure used to produce perspective illustrations from elevations. Tried it, but you do need a large drawing board to accommodate the vanishing points. Possibly a bit more info on what you are trying to do might bring forward some more concrete ideas - the strength of a forum is in it's collective wisdom. Link to post Share on other sites More sharing options...
Hitchin Junction Posted June 19, 2020 Share Posted June 19, 2020 The free CAD program GIMP may have that feature. Others here may know more. I thought my long ago TurboCAD SW had such a function , but I haven't used it for a decade or more, as it became quite expensive to keep up to date. So I never tried it. Any CAD program that can download a .jpg picture into its workspace and scale it, will give you a head start. Then you can use geometry to make frames you can measure. Tim Link to post Share on other sites More sharing options...
ardbealach Posted June 19, 2020 Share Posted June 19, 2020 Think Google Sketch up lets you do this. (AM) Link to post Share on other sites More sharing options...
Yardman Posted June 19, 2020 Share Posted June 19, 2020 It all depends how accurate you want to be. All photos can suffer from lens distortion, focal length changes and distortion due to perspective. If there is a known dimension in the photo such as a building brick you can count them up and have a reasonable idea of the size of a structure. Other known factors like wheel diameter can be a help. A lot depends on what your photo is like and if you are building something from scratch or just adding details to a model. 1 Link to post Share on other sites More sharing options...
Quarryscapes Posted June 19, 2020 Share Posted June 19, 2020 First off if you have a good elevation, then you can use image manipulation software to correct perspective/distortion etc and get it just right. 2nd import your clean image into CAD software / graphics software and draw your drawing over it. There are usually tools for calibrating background 'canvas' images. Something you may find useful for none dead on shots is using Cross ratio to find dimensions along perspective lines. Again this is best done in CAD where you can layout your lines and accurately measure to your vanishing point etc, It takes a bit of brain work but it is very useful to know. https://en.wikipedia.org/wiki/Cross-ratio#Projective_geometry Link to post Share on other sites More sharing options...
Simon Hartshorne Posted June 19, 2020 Author Share Posted June 19, 2020 (edited) Thanks so far. I too thought that Sketch Up could do it but I had a look this afternoon and it wasn’t obvious. I’ll look at Gimp. Thanks again. Edited June 19, 2020 by Simon Hartshorne Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted June 19, 2020 RMweb Gold Share Posted June 19, 2020 SketchUp (not owned by Google any more) has a "Photo Match" feature. It's in Sketchup Make, the last free desktop version, but I'm not sure about the online versions or the later subscription versions. https://help.sketchup.com/en/sketchup/matching-photo-model-or-model-photo 1 1 Link to post Share on other sites More sharing options...
Grovenor Posted June 20, 2020 Share Posted June 20, 2020 On 19/06/2020 at 18:15, Simon Hartshorne said: Thanks so far. I too thought that Sketch Up could do it but I had a look this afternoon and it wasn’t obvious. I’ll look at Gimp. Thanks again. Martin Wynne has done tutorials on using GIMP for this purpose, you should be able to find them on the TEMPLOT website. Link to post Share on other sites More sharing options...
Mark Saunders Posted June 20, 2020 Share Posted June 20, 2020 It would help if you mentioned what you want to build? This could lead to published drawings! Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted June 20, 2020 RMweb Gold Share Posted June 20, 2020 2 hours ago, Grovenor said: Martin Wynne has done tutorials on using GIMP for this purpose, you should be able to find them on the TEMPLOT website. http://www.templot.com/martweb/info_files/gimp_example.htm http://www.templot.com/martweb/info_files/gimp_track.htm Those pages are 18 years old, GIMP has a new user interface since then, but the functions work the same way. GIMP is free. Martin. 2 Link to post Share on other sites More sharing options...
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