3D Ball

# Based in an example program, a retake on a 3D simulation

graphsize 500,500
vx=.002
vy=.003
vz=.005
xball=1
yball=1
zball=1
while 1=1
a = mousex / 200
b = mousey / 200
gosub update
end while
update:
fastgraphics
clg
x=0
y=2
z=0
gosub matrix
x1=sx
y1=sy
x=2
y=0
z=0
gosub matrix
x2=sx
y2=sy
x=2
y=2
z=0
gosub matrix
x3=sx
y3=sy
color darkgreen
poly{200,200,x1,y1,x3,y3,x2,y2}
xball=xball+vx
yball=yball+vy
zball=zball+vz
vz=vz-.0005
if xball>2 then vx=-vx
if xball<0 then vx=-vx
if yball>2 then vy=-vy
if yball<0 then vy=-vy
if zball<0 then vz=-vz*.98
color black
x=xball
y=yball
z=0
gosub matrix
chord sx,sy,10,5-((y1+y2+y3)/100),0,pi*2
color red
x=xball
y=yball
z=zball
gosub matrix
circle sx,sy,5

if y3<200 then
color darkyellow
poly{200,200,x1,y1,x3,y3,x2,y2}
end if
refresh
clg
return
matrix:
u = x
v = y
w = z
u2 = u * cos(a) - v * sin(a)
v2 = u * sin(a) + v * cos(a)
w2 = w
u = u2
v = v2
w = w2
u2 = u
v2 = v * cos(b) - w * sin(b)
w2 = v * sin(b) + w * cos(b)
u = u2
v = v2
w = w2
sx = 200+u * (w + 2) * 35
sy = 200+v * (w + 2) * 35
return