option explicit
option default FLOAT

' 3D wire frame graphics demo using quaternions to rotate the coordinates
dim rotq(4),v(4),vout(4),i%,x1,y1,z1,x2,y2,z2,vertex
' define the coordinates of a cube with the z-axis towards the viewer
' coordinates of the cube
dim cube(3,7)=(-100,-100,100,0, -100,100,100,0, 100,-100,100,0, 100,100,100,0, -100,-100,-100,0, -100,100,-100,0, 100,-100,-100,0, 100,100,-100,0)
' define the coordinate pairs that make up the edges of the cube
dim cubelocation(2)=(mm.hres/2,MM.VRES/2,-500) 'actual location of the centre of the cube in space
' define the coordinate pairs that make up the edges of the cube
dim cubelines%(1,11)=(0,1, 0,2, 1,3, 2,3, 4,5, 4,6, 5,7, 6,7, 0,4, 1,5, 2,6, 3,7)
'define the projection plane
dim viewplane = -200
dim lines%(3,11) 'storage for the coordinates for lines drawn

for i%=0 to 7 'convert coordinates to normalised form
 x1=cube(0,i%)
 y1=cube(1,i%)
 z1=cube(2,i%)
 math q_vector x1,y1,z1,v()
 cube(0,i%)=v(1)
 cube(1,i%)=v(2)
 cube(2,i%)=v(3)
 cube(3,i%)=v(4)
next i%

'create a quarternion to rotate 2 degrees about x axis
'play with the x,y,z vector which is the sxis of rotation
math q_create rad(2), 1,0,0, rotq()
'draw lines in memory (page 1)
page write 1
do
 cls
 for i%=0 to 11 'project the coordinates onto the viewplane
   vertex=cubelines%(0,i%)
   z1=cube(2,vertex)*cube(3,vertex)+cubelocation(2)
   x1=(cube(0,vertex)*cube(3,vertex)*viewplane/z1+cubelocation(0))
   y1=(cube(1,vertex)*cube(3,vertex)*viewplane/z1+cubelocation(1))

   vertex=cubelines%(1,i%)
   z2=cube(2,vertex)*cube(3,vertex)+cubelocation(2)
   x2=(cube(0,vertex)*cube(3,vertex)*viewplane/z2+cubelocation(0))
   y2=(cube(1,vertex)*cube(3,vertex)*viewplane/z2+cubelocation(1))

   lines%(0,i%)=x1 : lines%(1,i%)=y1
   lines%(2,i%)=x2 : lines%(3,i%)=y2
 next i%
 for i%=0 to 7 'rotate coordinates
   v(1)=cube(0,i%) 'X
   v(2)=cube(1,i%) 'Y
   v(3)=cube(2,i%) 'X
   v(0)=cube(3,i%) 'magnitude
   v(4)=0
   math q_rotate rotq(),v(),vout()
   cube(0,i%)=vout(1) 'X
   cube(1,i%)=vout(2) 'Y
   cube(2,i%)=vout(3) 'Z
   cube(3,i%)=vout(0) 'magnitude
 next i%
 
 for i%=0 to 11 'draw the new lines
   line lines%(0,i%),lines%(1,i%),lines%(2,i%),lines%(3,i%),1,rgb(white)
 next i%
 'copy page 1 to the screen (page 0)
 page copy 1 to 0
loop
end