"Greg M. Johnson" wrote:

> In my systems,
>     #declare velocity=velocity-0.1*y;
> is how I usually do gravity.

IMHO I think my advice is the best here for frame-by-frame pov coding of gravity.

> #declare velocity=velocity-dragconstant*velocity^2;
> where dragconstant=0.005;   //for starters

Oops!  an error above.

//   for a frame-by-frame system, experiment with small numbers for drag; toss
textbook values in dustbin.
#declare dragconstant=0.005;

//   Wind is some varying vector.
#declare wind=foo;

//   Wind blowing at craft means double effect; blowing with craft negates
effect.
#declare netdirection=wind-velocity;

//   I forgot that velocity was a vector in last version I shared.
#declare
velocity=velocity+vnormalize(netdirection)*dragconstant*vlength(netdirection)^2;

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