How to check if two rectangles intersect? Each rectangle is defined by three points in 2d space. The rectangles can be rotated around any point as on the image below.
I hope this helps $\ddot\smile$
If they can be rotated around any point (or corner by the way).
Take rectangle $R_1$ with corners $A_1$, $B_1$ etc.
You have four circles of center $A_1$, $B_1$ etc. and of radius $A_1C_1$, $B_1D_1$ etc.
You just have to check if any of these four circle intersect with any of the four other circles defined the same way with rectangle $R_2$ (points $A_2$, $B_2$ and radii $A_2C_2$ etc.).