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Is there any way to find the scale of the orthographic camera so that it matches the view field from the perspective camera? So for example if I render a plane in perspective mode and I see a certain part of the plane on that image without knowing how large this part is in blender units, how do I set the orthographic camera to see the exact same image?

Or to put it differently, if two points are exactly one pixel apart on a plane at a certain distance in perspective mode with a certain focal length, I need them to also be one pixel apart at orthographic mode and I'm missing the orthographic scale.

And again, I don't really have any information about the size of the view in blender units, so I hope there's a solution that only needs the distance of the plane to the camera and the focal length of the perspective camera.

Marius
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  • This is related to the camera focal length math, which in turn is related to physics outside of blender. Find out the rules of how focal length and sensor size affects the broadness of the camera, and then do a spot of trigonometry. I expect the result will be easy to work with. – TheLabCat Jun 09 '21 at 02:19
  • Related https://blender.stackexchange.com/a/128197/15543 and https://blender.stackexchange.com/questions/95989/is-there-a-way-to-get-the-dimensions-of-the-camera – batFINGER Jun 09 '21 at 02:50

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As @ZargulTheWizard has stated, there's a simple solution to this problem. By using the formula object size in image = focal length * object size / object distance and knowing that the object size in image is the sensor size, I can calculate the visible part of the plane in blender units and therefore get the scale factor

Marius
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