[Enigma-devel] marble movement code

[Petr Machata]

I played a bit with the "new movement code" from CVS. It behaves rather 
well on common floor, but problems arise with the gradients and gravity 
levels at all. The gravity currently doesn't look much like gravity, as 
the marble stops accelerating very early. The problem with gradients is 
similar - they are no great deal, behaving nearly as common floors. 
Well, I tried to play with it a bit, and there is what came out of my tests.

The simplest solution seems to multiply the gravity forces by some 
constant. I tried several numbers, and for gravity the coefficient of 
2.5 seems to be quite good. Greater numbers mean that marble nearly 
doesn't bounce, which also does not look well. I tried "swoop" 
(martin01.lua) and "Skydiver" (martin13.lua) with those settings and it 
beehaved well.

Next chapter: gradients. Modifiyng Gradient::get_force so that it 
returns 50*force does the job well, imho - again, multiplication is 2.5, 
no wonder.

Hand in hand with these changes goes the change of the movement factors. 
Well, for me, Mouse speed of 3, Mouse damping of 50 and Friction factor 
of 1.0 worked well. I played several levels with those settings (that 
is, some gravity levels, some common, some gradients) and felt it to be 
good. Understand: movement over common floors was nearly as good as 
before, gravity looked like gravity, marble bounced as expected from 
well-behaved, gravity-attracted marble, and gradients were pushing the 
marble in the right direction with some real force.

I rather liked old enigma's marble motion engine, marble very 
sensitively reacted to mouse movements, and also wanted to have the 
gravity looking good and gradients be some problem for the player. This 
all meaned low Friction factor. High Damping is because the mouse on 
common floor was too "liveful" - due to low Friction, of course. Ditto 
for low Mouse speed.

I have no comparsion to original OXYD, nor to some of its clones. Long 
ago I had Per.OXYD on my windows x86, and even longer before OXYD II on 
Atari, but these both are now graved deep to dust.

I found these values on Linux (SuSE 7.3, if this helps you a bit).

I hope this will do some good.
Have a nice day.
Ant