Scaling - How To (Tutorial)

[darren s]

Just thought I'ld share a tip with you guys, tryed putting it in the Wiki but don't know how to.

So, this "tutorial" is about scaling. Have you been dying to make a building and not knowing the height? I have. With measurments of only width and length, I discoverd how to work out the height of the building using these, in my case I used the width.
Well I have been making the control tower on my EGBG scenery, using google earth to find out the width and length was a walk in the park, one thing was bugging me - "What is the height?"
Well, after searching around for a picture of the control tower, I finally fount one which is direct to the building. I will go through this with you using my project.

Well after getting the direct-on-face photo of the control tower (front), I knew that this is the width, the width in real life is 11.5 Meters (1150CM).

I then got a see-through ruler and measured the picture on the screen, this read 6.8CM.

I then worked out that a meter in real life was scaled to 0.591304347826087 CM in my picture. I got his by doing this sum 6.8÷11.5. Giving me the scale of 1M to 0.591304347826087. I then rounded this to the nearest 0.1 which gave me 0.6CM/6MM.

I then rotated my ruler 90° to measure the top to bottom, this read 4.2CM. Because from earlier I know that 1M in real life represents 0.6CM on my picture, so I then done 4.2÷0.6 which gave me 7. So to my scale measuring ect, the the height of this building is 7M.

So for step by step -
1: Get the picture, try and get a direct on face one for precision.
2: Find the width of the building using GE, remember Use width for the FRONT! and Length for the SIDE!
3: Measure the width of the picture (front of building) on your screen using a real ruler. Get it to the nearest MM
4: Use your answer from the above step and divide it by the real width
(4a)-----The answer from the above step is the scale----
5: Rotate the ruler 90 degrees and measure from the roof down to the floor
6: The answer from above, divide it by your scale you got from step 4.
(6a)----The answer from above is the height of the building----

Happy modelling

 

[Robert John]

I am not to sure but don't pictures have different field of views depending on camera lens used.Ie Forshortening. Foreshortening - What is Foreshortening Foreshortening is when an object appears compressed when seen from a particular viewpoint, and the effect of perspective causes distortion.
I think you will have to use a few photos of the same building from different distances and take a average.
Good reference tutorial.
Robert John

 

[darren s]

I am not to sure but don't pictures have different field of views depending on camera lens used.Ie Forshortening. Foreshortening - What is Foreshortening Foreshortening is when an object appears compressed when seen from a particular viewpoint, and the effect of perspective causes distortion.
I think you will have to use a few photos of the same building from different distances and take a average.
Good reference tutorial.
Robert John

Well since I already know the width of the building in real life, i scaled this on the picture, then measured the height. I dont this because I wasn't allowed to measure the control tower, but I have actually just got back from the airport as they allowed me to measure the height and my scaling technique to find the height, was correct to real world

 

[FelixFFDS]

Robert - the key in his tutorial is that he had a good "face on" front photograph and knows the width of the building - so any photographic distorition due to view is minimized (within the realm of tolerance for scale modelling).

FOr modelling purposes, though, I'd let my modelling program do the scaling.

for gmax: I would map the photograph to a plane then make a separate object of the exact (known) length, freeze it in place. Then I'd scale the mapped plane so that the width of the "building" matches the known-length object.

for FSDS: I would load the photograph as the backdrop image, the go to the scale dialog... click on one end of the building, click on the other, type in the known distance, click "ok" and the image is scaled automatically.

If all is done well, you go back into the "scale" dialog and see the scale factor.

I am not to sure but don't pictures have different field of views depending on camera lens used.Ie Forshortening. Foreshortening - What is Foreshortening Foreshortening is when an object appears compressed when seen from a particular viewpoint, and the effect of perspective causes distortion.
I think you will have to use a few photos of the same building from different distances and take a average.
Good reference tutorial.
Robert John

 

[darren s]

Robert - the key in his tutorial is that he had a good "face on" front photograph and knows the width of the building - so any photographic distorition due to view is minimized (within the realm of tolerance for scale modelling).

FOr modelling purposes, though, I'd let my modelling program do the scaling.

for gmax: I would map the photograph to a plane then make a separate object of the exact (known) length, freeze it in place. Then I'd scale the mapped plane so that the width of the "building" matches the known-length object.

for FSDS: I would load the photograph as the backdrop image, the go to the scale dialog... click on one end of the building, click on the other, type in the known distance, click "ok" and the image is scaled automatically.

If all is done well, you go back into the "scale" dialog and see the scale factor.

Nice, I never thought of that.

And yes, Face on photos so there is no distortion...allthough it will still work, it would just be very awkward to do.

I like your idea though, I know exactley what you mean

 

[Robert John]

I think this has been a interesting thread and with all this knowledge Could be put into a good tutorial.

 

[darren s]

I think this has been a interesting thread and with all this knowledge Could be put into a good tutorial.

Yes, I have tried to add it to the Wiki but I don't know how to do it.