[Freeciv-Dev] (PR#7402) Drawing speed

["Arnstein Lindgard" <a-l@xxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=7402 >

About the efficiency of drawing-to-screen:

With a 1 GHz CPU, I found that I could copy the entire backing store
of the map canvas to screen 50 times pr second (1024 screen window),
and that consumed just above 50% of the available CPU cycles. When
scrolling, the other half is consumed by tile updates.

Then I upgraded my Radeon linux drivers and got a 13X speedup..(after
first trying the hard way and discussing optimizations with Vasco and
Jason :) So the hardware blitter kicked in. GeForce is a more popular
brand, so the problem probably goes away entirely for most players
since that company is older and has even better drivers.

Since the client should get a 50-60 fps redraw timer anyway, it
should probably also redraw the overview canvas when required, so
nobody has to worry about inefficiency with respect to that. I think
it's wrong to have the programmer think about when redraws occur
(with flush_dirty() everywhere).

Dirty Rectangles may still make sense for machines with slow CPU and
bad drivers.

Players should be aware that upgrading the X graphics driver may help
*a lot* in some cases, since the updating process performs thousands
of small blits (pixmap to pixmap) when building the tiles, and help
even more when scrolling goes in. If we write that in the docs, point
out it's a matter of drivers, not price of the card. Read: I should
have bought NVIDIA, not ATI, although the latter is coming along
[sarcasm ON] just a few decades behind the Amiga [sarcasm OFF]. If a
linux player really has a redrawing speed problem, he should try
running X at a lower color resolution.


Arnstein