1. Modify the DDA algorithm for negative sloped lines; discuss both the cases i.e., slope > 1 and 0 < slope < 1.

Ans. For the generation of lines along with negative slopes as:

 Slope < 1: successively raise y and respectively reduces x

Slope > 1: successively raise x and respectively reduces y

Aliter: This hint will use further.

As the shown above figure say L1 and L2 are lines along with -ive slope along with a magnitude of <1 and >1 respectively. So for the generation of that line, you may take reflection of the line regarding the concerned axis and obey the general algorithm of line generation. So then you may inverse reflection the transformation and this will offer you the line generation of -ive slope.