simplest inner loop part of a addition-only line-draw one slope case only. just to show the concept. |---- dy| ----- | ---- |_________________ dx int dx=8, dy=3; int x=0, y=0, acc=0; for (int i=0; i dx) { acc -= dx; y++; } } thinking help: the "trick" is to lay out the dy:s over the dx until it overflows, and that's where the ratio of dx/dy tells us to tick down the slope. dy --- --- --- -|-- --- --- --|- --- --- --- dx _____________|_____________|_____________ do y++ here this is how i did it on the 286 in asm, no floating point unit available. /Niklas Lundberg