CompuServe Thread

Smoking cigarettes! Hmph. Judging from the speed of your response you must also be one of us guys not at Siggraph. ——- Since you are into astronomy, you could have some fun with a program I played with last night. I started out by trying to compute the path of an object under the influence of two point masses. I got the effects I wanted after playing with the equations for a while, so I don't know if as it stands now, it has any connection to real motion under gravity. For one thing, the paths are chaotic. The object can orbit one of the masses many times, then suddenly move over to the other mass, and eventually catapult out of the screen, gaining speed all the time! Run it w/o changes (at 640×480). Then look at the path in Optics. You'll see what I was aiming for, a figure-8 path (like the one I used in "Sloshing Water " (ROLL69.ZIP) and "Flying Carpet" (ROLL56). In this case the object alternately orbits each of the masses. Now the starts, start changing the values! (I almost didn't get any sleep last night!). I am thinking of making the program into a more complete package ("Chaos with AniPro"). I was wondering about the user interface. When I use it, I prefer to just edit the program and change a value or two. But, for other users, is there a way to put up several sliders at once, or some way to modify several values with just one menu? Ed K ——————————— main() //two concentrated masses. figure 8 orbit 94 -7-24 //Copyright 1994. Ed Kellerman { #define n 202 int mass1_x = 200, mass1_y = 200; int mass2_x = 400, mass2_y = 200; double init_x = 300, init_y = 200, init_x_vel = 8, init_y_vel = 5, accel = 23.105; int t = 0, x[n], y[n]; Box(mass1_x,mass1_y,2,2); Box(mass2_x,mass2_y,2,2); double ii,last_y,last_x, a_x1,v_x1,a_y1,v_y1,dist1, a_x2,v_x2,a_y2,v_y2,dist2; last_x = init_x; last_y = init_y; v_x1 = init_x_vel; v_y1 = init_y_vel; v_x2 = init_x_vel; v_y2 = init_y_vel; for ( t = 0; t < n; t++) { dist1 = sqrt((last_x-mass1_x)*(last_x-mass1_x) + (last_y-mass1_y)*(last_y-mass1_y)); dist1 = pow(dist1,2); dist2 = sqrt((last_x-mass2_x)*(last_x-mass2_x) + (last_y-mass2_y)*(last_y-mass2_y)); dist2 = pow(dist2,2); a_x1 = accel * (mass1_x-last_x) / dist1; a_y1 = accel * (mass1_y-last_y) / dist1; a_x2 = accel * (mass2_x-last_x) / dist2; a_y2 = accel * (mass2_y-last_y) / dist2; // v_x1 = v_x1 + a_x1; v_y1 = v_y1 + a_y1; v_x1 = v_x1 + a_x1 + a_x2; v_y1 = v_y1 + a_y1 + a_y2; // for ( ii = 0; ii<400; ii++) {printf("%f %f",a_x1,a_x2);} last_x = last_x + v_x1; last_y = last_y + v_y1; x[t] = last_x; y[t] = last_y; } OptSetPath(n,x,y); }

>>But Ed, everyone knows that the real reason dinosaurs got wiped out was >>from smoking cigarettes (don't you read Gary Larson?) 🙂 But Dave, everyone knows that the real reason dinosaurs got wiped out was because they built a wax-fruit factory over the swamp where certain giant beetles mated. Because they wiped out the beetles, there was nothing to curtail the kudzu-like Cider-Poppy vines, which threatened to choke the planet. The WeSaySo Corp (who of course, built the wax-fruit plant in the first place) decided to use a really-strong defoliant — which killed all plant life on earth. Then, WeSaySo thought, well, to make plants grow, we need rain. Rain comes from clouds. Volcanos make clouds, so we can just put some bombs in a volcano, and viola!, clouds/rain/plants! The subsequent dust cloud shrouded the planet in darkness, causing the death of all non-mammalian life on earth (don't you watch ABC's "Dinosaurs" sitcom?) 🙂 Dave