Hmm, probably my fault (just got the 30-days trial) but if I copy this and save it as a upr, it tells me "contains errors"
Hmmm... Did you try copying and pasting into another open fractal instead of saving it as a upr? Here's an uncompressed version so you can read what the layers are and how they're colored. I've attached the image (except, I changed the colors and modes a bit, but the orbits are the same).
GravitySample {
; copyright Kerry Mitchell 27jan2000
fractal:
title="Gravity Sample" width=480 height=480 layers=4
credits="Kerry Mitchell;1/27/2000"
layer:
caption="comet 3" opacity=25 method=multipass
mapping:
center=0/0 magn=1
formula:
maxiter=628 percheck=off filename="lkm.ufm" entry="gravity3-comet"
p_zc0=-2/-0.2 p_vc0=1/0 p_z10=1/0 p_z20=-0.5/0.866025403784438647
p_z30=-0.5/-0.866025403784438647 p_v10=0/1
p_v20=-0.866025403784438647/-0.5 p_v30=0.866025403784438647/-0.5
p_mass1=3.466 p_mass2=3.466 p_mass3=3.466 p_timestep=0.01
p_ztype="comet position" p_bailout=1000
inside:
transfer=cuberoot filename="lkm.ucl" entry="basic"
p_colorby=magnitude
outside:
transfer=linear
gradient:
smooth=yes index=0 color=16777215 index=50 color=14532495 index=100
color=11829312 index=150 color=8405008 index=200 color=0 index=250
color=8405008 index=300 color=11829312 index=350 color=14532495
opacity:
smooth=no index=0 opacity=255
layer:
caption="comet 2" opacity=33 method=multipass
mapping:
center=0/0 magn=1
formula:
maxiter=628 percheck=off filename="lkm.ufm" entry="gravity3-comet"
p_zc0=-2/-0.1 p_vc0=1/0 p_z10=1/0 p_z20=-0.5/0.866025403784438647
p_z30=-0.5/-0.866025403784438647 p_v10=0/1
p_v20=-0.866025403784438647/-0.5 p_v30=0.866025403784438647/-0.5
p_mass1=3.466 p_mass2=3.466 p_mass3=3.466 p_timestep=0.01
p_ztype="comet position" p_bailout=1000
inside:
transfer=cuberoot filename="lkm.ucl" entry="basic"
p_colorby=magnitude
outside:
transfer=linear
gradient:
smooth=yes index=0 color=16777215 index=50 color=9428415 index=100
color=4240512 index=150 color=1081408 index=200 color=0 index=250
color=1081408 index=300 color=4240512 index=350 color=9428415
opacity:
smooth=no index=0 opacity=255
layer:
caption="comet 1" opacity=50 method=multipass
mapping:
center=0/0 magn=1
formula:
maxiter=628 percheck=off filename="lkm.ufm" entry="gravity3-comet"
p_zc0=-2/0 p_vc0=1/0 p_z10=1/0 p_z20=-0.5/0.866025403784438647
p_z30=-0.5/-0.866025403784438647 p_v10=0/1
p_v20=-0.866025403784438647/-0.5 p_v30=0.866025403784438647/-0.5
p_mass1=3.466 p_mass2=3.466 p_mass3=3.466 p_timestep=0.01
p_ztype="comet position" p_bailout=1000
inside:
transfer=cuberoot filename="lkm.ucl" entry="basic"
p_colorby=magnitude
outside:
transfer=linear
gradient:
smooth=yes index=0 color=16777215 index=50 color=12554205 index=100
color=8405172 index=150 color=4198528 index=200 color=0 index=250
color=4198528 index=300 color=8405172 index=350 color=12554205
opacity:
smooth=no index=0 opacity=255
layer:
caption="stars" opacity=100 method=multipass
mapping:
center=0/0 magn=1
formula:
maxiter=628 percheck=off filename="lkm.ufm" entry="gravity3-comet"
p_zc0=-2/0 p_vc0=1/0 p_z10=1/0 p_z20=-0.5/0.866025403784438647
p_z30=-0.5/-0.866025403784438647 p_v10=0/1
p_v20=-0.866025403784438647/-0.5 p_v30=0.866025403784438647/-0.5
p_mass1=3.466 p_mass2=3.466 p_mass3=3.466 p_timestep=0.01
p_ztype="all stars" p_bailout=1000
inside:
transfer=cuberoot filename="lkm.ucl" entry="basic"
p_colorby=magnitude
outside:
transfer=linear
gradient:
smooth=yes index=0 color=16777215 index=100 color=8421504 index=200
color=0 index=300 color=8421504
opacity:
smooth=no index=0 opacity=255
}