Blitter Line reverse drawing question

[sandruzzo]

Currently I'm drawing line from top to bottom, I would like to reverse order. Is there any fast trick way to do that?

Thanks in Advance

[DanScott]

just swap the coordinates

[sandruzzo]

Doesn't work like that. Order is still top to bottom

[Thomas Richter]

Originally Posted by sandruzzo

Doesn't work like that. Order is still top to bottom

Err, if you setup the blitter control blits, it can draw lines in all of the 8 possible octants. Or use graphics/Draw(), which does all the computation for you.

[Toni Wilen]

Most optimized blitter line routines swap coordinates if direction is "wrong" because it makes rest of calculation (octanct etc) simpler and faster.

[sandruzzo]

I and using an optimized one, that allways draw top to bottom

[Photon]

Then I think the routine is made to do that. That is, you swap the coordinates and then call the routine, and the routine does what it's made to do, takes lines pointing upward or downward, and swap the coordinates to draw all lines downward.

To fix it, look in the routine. There should be a subtract to create delta values for X and Y. Then, look for a test for the sign of delta Y. Reverse the test.

But if it's optimized, it's not made for that (only has 4/8 octants, the downward pointing ones). This means a rewrite of the routine.

[sandruzzo]

@Photon

Yes, it's optimized and use octant' symmetry, that's way swapping coordinate don't work. I

[LaBodilsen]

Originally Posted by sandruzzo

@Photon

Yes, it's optimized and use octant' symmetry, that's way swapping coordinate don't work. I

just put you screen pointer to the bottom of your bitmap, and set module to -80

(just kidding of course)

[sandruzzo]

@LaBodilsen

Partial working: x is flipped too! I'm using line drawing to simulate rope swing, so, all it's up-side down!