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Peter's algorithm states:
#declare NewVel[i] = OldVel[i] + Acceleration*Time;
#declare NewPos[i] = OldPos[i] + OldVel[i]*Time + 0.5*Acceleration*Time*Time;
I think d= d0 +vt + at^2 only applies in the case of constant acceleration!
I prefer:
#declare NewVel[i] = OldVel[i] + Acceleration*Some_Constant;
#declare NewPos[i] = OldPos[i]+NewVel[i]*Acceleration*Some_Other_Constant;
Also, I tend not to bother with the "time", as I run my particle systems inside a
#while
loop. It eliminates the need to write to a file for each frame. For example, in a 250
frame
animation, I say,
#while(Gregs_Frame_Increment < 250*clock+1)
Ben Birdsey wrote:
> I seem to have gotten the program working. There was a problem with the
size
> of "GravConst" (i.e. = 6.670e0 instead of = 6.670e-11). I also took the liberty
> of changing the units that the data is stored in (all in AU's and years and
> earth masses. This is easier for us because that's what's in the tables, but
> the computer has to convert).
>
> I don't know what problems you were experiencing, but at first, my mercury
kept
> breaking out of orbit! I was trying to use an algorithm called "Velocity
> Verlet" to integrate, but it was unstable at a time step of even 8 hours! So, I
> went back to your original method and it works.
>
> In Him,
> Ben
>
> ------------------------------------------------------------------------
>
> Name: gravity2.zip
> gravity2.zip Type: Zip Compressed Data (application/x-zip-compressed)
> Encoding: base64
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