private static Rectangle CalcLocalScissorAABB(Matrix32 transform)
{
// Get the scissor rectangle in 0,0 - 1,1 coordinate space
var vp = new Rectangle {
A = new Vector2(viewport.X, viewport.Y),
B = new Vector2(viewport.X + viewport.Width, viewport.Y + viewport.Height)
};
var r = (Rectangle)(IntRectangle)scissorState.Bounds;
var scissorRect = new Rectangle {
A = (r.A - vp.A) / vp.Size,
B = (r.B - vp.A) / vp.Size
};
// Transform it to the normalized OpenGL space
scissorRect.A = scissorRect.A * 2 - Vector2.One;
scissorRect.B = scissorRect.B * 2 - Vector2.One;
// Get the unprojected coordinates
var invProjection = Projection.CalcInverted();
var v0 = invProjection.ProjectVector(scissorRect.A);
var v1 = invProjection.ProjectVector(new Vector2(scissorRect.B.X, scissorRect.A.Y));
var v2 = invProjection.ProjectVector(scissorRect.B);
var v3 = invProjection.ProjectVector(new Vector2(scissorRect.A.X, scissorRect.B.Y));
// Get coordinates in the widget space
var invTransform = transform.CalcInversed();
v0 = invTransform.TransformVector(v0);
v1 = invTransform.TransformVector(v1);
v2 = invTransform.TransformVector(v2);
v3 = invTransform.TransformVector(v3);
var aabb = new Rectangle {
A = v0, B = v0
}.
IncludingPoint(v1).
IncludingPoint(v2).
IncludingPoint(v3);
return(aabb);
}