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Question by Kras · Jan 12 at 07:43 PM · vector math

Projected plane area?

I'm beginner in coding and i faced this problem: I have a rotated plane in xyz, and a game object. I need the projected plane area form other game object plane of view. alt text

How should i get the projected plane area?

rotated-plane-area.png (17.0 kB)
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avatar image Bunny83 · Jan 12 at 11:18 PM 0
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Uhm what kind of camera do you use? Keep in mind that a rotated rectangle in a perspective camera will yield a Trapezoid. Also do you want to project the plane onto a plane that is parallel to the camera / screen plane?

avatar image Kras Bunny83 · Jan 13 at 11:46 PM 0
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I need this area for calculating force on the sail from wind point of view.

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Answer by Bunny83 · Jan 14 at 12:25 AM

Ok for a sail on a sailboat you need two things:


  • Calculate the actual area that the sail has.

  • You also need the normal vector of the sail. So the vector that is perpendicular to the surface of the sail.


Now all you have to do is this:

 float affectedArea = sailArea * Mathf.Abs (Vector3.Dot(windDir, sailNormal));


Note that windDir as well as sailNormal need to be normalized vectors (vectors with a length of 1.0). If your sail is a gameobject you can simply get the normal from one of the local axis vectors (forward, right, up) which are already normalized. Just pick the right one. sailArea is just a float value which should be equal to the area of your sail.

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avatar image Kras · Jan 14 at 09:03 PM 0
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That was exactly what i needed! Thank You!

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