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Deciding which is dimension is which for rotated quadrangles.

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I'm creating a quadrangle using the following method:

// Lower Left -- [d]
// Upper Left | |
// Lower Right | |
// Upper Right [a] -- [c]

quadrangle = new Quadrangle(
(a + d) * 0.5f, // Position
Vector3.Distance(b, d), // Width
Vector3.Distance(b, a), // Height
Vector3.Normalize(Vector3.Cross(b - a, c - a)), // Normal
64 // Texture Index

The constructor then rotates the quadrangle so that its normal faces in the direction specified:

private static Matrix RotationFrom(Vector3 normal)

Matrix rotation = Matrix.Identity;
rotation.Backward = normal;
rotation.Up = Vector3.Cross(Vector3.UnitY, normal);

if (rotation.Up.LengthSquared() < MathTools.EPSILON)
rotation.Up = Vector3.Cross(-Vector3.UnitZ, normal);

rotation.Right = Vector3.Cross(rotation.Up, normal);

return rotation;

The problem is that this ruins the method for finding the width and height as they can be swapped around depending on quadrangle orientation. How can I make sure that the dimensions are set correctly so that when the quadrangle transform is scaled:

worldTransform.M11 *= scale.X;
worldTransform.M12 *= scale.X;
worldTransform.M13 *= scale.X;
worldTransform.M21 *= scale.Y;
worldTransform.M22 *= scale.Y;
worldTransform.M23 *= scale.Y;

It takes into account the current orientation?


width ------>

-- [d] ^
| | |
| | |
[a] -- [c] height



[a] -- ^
| | |
| | |
[c] -- [d] width

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