Polygon Clipping

 Discard whole polygon if any vertex lies outside of canvas boundaries.

Scan conversion

Read section 3.6

All special cases should be covered automatically by the correct implementation of the algorithm (concave, degenerate).

Floating point coordinates.

Initial point calculation:

DX = X2 - X1
DY = Y2 - Y1

P_initial = ( X1 + Xd, ceil(Y1) )

Using similar triangles:

Xd  /  ( ceil(Y1) - Y1 )  =  DX / DY  =>

Xd = ( ceil(Y1) - Y1) * DX / DY

Updating Edge intersection for next scan line:

Current P = ( X, Y )
Next      P = ( X + Xinc, Y + 1 )

Xinc =  DX / DY