CompuServe Messages

For direction, try LOOK_AT(SPLINE(T+1)) or LOOK_AT(SPLINE(T+1)+SPLINE(T)-SPLINE(T-1)). I think the second one will giver better results. In order to vary the speed, you can calculate 100 times as many spline points, and then increase T by SPEED/100 (and use int(T) in all SPLINE statments). For a rollercoaster, SPEED = sqrt(H-Y). Where Y = the hight of the camera, and H is some hight HIGHER than the highest point on the ride. The higher H is, the faster the ride. Hmmm, that ignores friction. For a rollercoaster with friction, SPEED = sqrt(H*POW(F,T)-Y). Where F=friction (just under 1.0 , around 0.999 is reasonable). Note: If H is too low, and/or F is too far below 1.0, you will get an error, SQRT(negative number). If you use E=H*POW(F,T)-Y (or E=H-Y) and SPEED=sqrt(abs(E))*sign(E)*sign(SPEED(T-1)), you won't get the sqrt(negative) error, and the camera will run backwards if it can't get over a hill (like a real roller coaster, and it you are using friction, it will rock back and forth and come to a stop at the bottom). P.S. sign(X)= if (X<0) then return -1 else return 1 or sign(X)=X/abs(X) (You may want to test for X=0 first, and return 1 if X=0, but if X ever equals 0, it means SPEED=0.) P.P.S I can imagine cases where this might get stuck and act real weird when it can't make it over a hill and tries to back up. Hmmm… E=H*POW(F,T)-Y (or E=H-Y) and SPEED=sqrt(abs(E))*D should work (start with D=1), but each frame test if sign(E) < 0, and if it is then DON'T change T, but make D=-D. I just realized the camera will turn around in all the examples where it goes backwards. In the spline statements, if you change T+1 to T+D and T-1 to T-D, the camera won't turn around when you back up. Ask if anything is confusing. Read action !