Separating Axis Theorem and Python

Question

This is what I am currently doing:

Creating 4 axis that are perpendicular to 4 edges of 2 rectangles. Since they are rectangles I do not need to generate an axis (no

Answer 1

I see two things wrong. First, the projection should simply be the dot product of a vertex with the axis. What you're doing is way too complicated. Second, the way you get your axis is incorrect. You write:

Axis1 = [  -(A_TR[0] - A_TL[0]),
             A_TR[1] - A_TL[1] ]

Where it should read:

Axis1 = [  -(A_TR[1] - A_TL[1]),
             A_TR[0] - A_TL[0] ]

The difference is coordinates does give you a vector, but to get the perpendicular you need to exchange the x and y values and negate one of them.

Hope that helps.

EDIT Found another bug

In this code:

if not ( B_Scalars[0] <= A_Scalars[3] or B_Scalars[3] >= A_Scalars[0] ):
            #no overlap so no collision
            return 0

That should read:

if not ( B_Scalars[3] <= A_Scalars[0] or A_Scalars[3] <= B_Scalars[0] ):

Sort gives you a list increasing in value. So [1,2,3,4] and [10,11,12,13] do not overlap because the minimum of the later is greater than the maximum of the former. The second comparison is for when the input sets are swapped.