1 BORDER 0: PAPER 0: INK 9: BRIGHT 1: CLS 
    10 LET spheres=2: IF spheres THEN DIM c(spheres,3): DIM r(spheres): DIM q(spheres)
    20 FOR k=1 TO spheres: READ c(k,1),c(k,2),c(k,3),r: LET r(k)=r: LET q(k)=r*r: NEXT k
    30 DATA -0.3,-0.8,3,0.6
    40 DATA 0.9,-1.1,2,0.2
    50 FOR i=0 TO 175: FOR j=0 TO 255
    60 LET x=0.3: LET y=-0.5: LET z=0
    70 LET dx=j-128: LET dy=88-i: LET dz=300: LET dd=dx*dx+dy*dy+dz*dz
    80 GO SUB 100: NEXT j: NEXT i
    90 STOP 
   100 LET n=-(y>=0 OR dy<=0): IF NOT n THEN LET s=-y/dy
   110 FOR k=1 TO spheres
   120 LET px=c(k,1)-x: LET py=c(k,2)-y: LET pz=c(k,3)-z
   130 LET pp=px*px+py*py+pz*pz
   140 LET sc=px*dx+py*dy+pz*dz
   150 IF sc<=0 THEN GO TO 200
   160 LET bb=sc*sc/dd
   170 LET aa=q(k)-pp+bb
   180 IF aa<=0 THEN GO TO 200
   190 LET sc=(SQR bb-SQR aa)/SQR dd: IF sc<s OR n<0 THEN LET n=k: LET s=sc
   200 NEXT k
   210 IF n<0 THEN RETURN 
   220 LET dx=dx*s: LET dy=dy*s: LET dz=dz*s: LET dd=dd*s*s
   230 LET x=x+dx: LET y=y+dy: LET z=z+dz
   240 IF n=0 THEN GO TO 300
   250 LET nx=x-c(n,1): LET ny=y-c(n,2): LET nz=z-c(n,3)
   270 LET l=2*(dx*nx+dy*ny+dz*nz)/q(n)
   280 LET dx=dx-nx*l: LET dy=dy-ny*l: LET dz=dz-nz*l
   290 GO TO 100
   300 FOR k=1 TO spheres
   310 LET u=c(k,1)-x: LET v=c(k,3)-z: IF u*u+v*v<=q(k) THEN RETURN 
   320 NEXT k
   330 IF (x-INT x>.5)<>(z-INT z>.5) THEN PLOT j,i
   340 RETURN
 

• contrib_raytracing.bas

The instructions here refer to compiling the example from the command line. For Microsoft Windows users we suggest using UGBASIC-IDE, which allows you to compile the example with just one click.

In order to compile and run the example, you need to have the Altirra emulator, and in particular that the altirra executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.atari contrib_raytracing.bas -o example.xex
 altirra example.xex
 
 # Windows 
 ugbc.atari.exe contrib_raytracing.bas -o example.xex
 altirra example.xex

In order to compile and run the example, you need to have the Altirra emulator, and in particular that the altirra executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.atarixl contrib_raytracing.bas -o example.xex
 altirra example.xex
 
 # Windows 
 ugbc.atarixl.exe contrib_raytracing.bas -o example.xex
 altirra example.xex

In order to compile and run the example, you need to have the VICE emulator, and in particular that the x64sc executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.c64 contrib_raytracing.bas -o example.prg
 x64sc example.prg
 
 # Windows 
 ugbc.c64.exe contrib_raytracing.bas -o example.prg
 x64sc example.prg

In order to run the example, you need to have the YAPE emulator. In particular that the yape executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.plus4 contrib_raytracing.bas -o example.prg
 yape example.prg
 
 # Windows 
 ugbc.plus4.exe contrib_raytracing.bas -o example.prg
 yape example.prg

In order to run the example, you need to have the VICE emulator. In particular that the xplus4 executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.plus4 contrib_raytracing.bas -o example.prg
 xplus4 example.prg
 
 # Windows 
 ugbc.plus4.exe contrib_raytracing.bas -o example.prg
 xplus4 example.prg

In order to compile and run the example, you need to have the XROAR emulator, and in particular that the xroar executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.d32 contrib_raytracing.bas -o example.bin
 xroar -rompath (your rom path) example.bin
 
 # Windows 
 ugbc.d32.exe contrib_raytracing.bas -o example.bin
 xroar.exe -rompath (your rom path) example.bin

In order to compile and run the example, you need to have the XROAR emulator, and in particular that the xroar executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.d64 contrib_raytracing.bas -o example.bin
 xroar -rompath (your rom path) example.bin
 
 # Windows 
 ugbc.d64.exe contrib_raytracing.bas -o example.bin
 xroar.exe -rompath (your rom path) example.bin

In order to compile and run the example, you need to have the DCMOTO emulator, and in particular that the dcmoto executable is accessible.

Then, type this command on the command line and on the emulator:

 # Linux 
 ugbc.pc128op contrib_raytracing.bas -o example.k7
 dcmoto
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC
 
 # Windows 
 ugbc.pc128op.exe contrib_raytracing.bas -o example.k7
 dcmoto
 (choose example.k7)
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC

In order to compile and run the example, you need to have the DCMOTO emulator, and in particular that the dcmoto executable is accessible.

Then, type this command on the command line and on the emulator:

 # Linux 
 ugbc.pc128op contrib_raytracing.bas -o example.k7
 dcmoto
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC
 
 # Windows 
 ugbc.pc128op.exe contrib_raytracing.bas -o example.k7
 dcmoto
 (choose example.k7)
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC

In order to compile and run the example, you need to have the VICE emulator, and in particular that the xvic executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.vic20 contrib_raytracing.bas -o example.prg
 xvic --memory 24k example.prg
 
 # Windows 
 ugbc.vic20.exe contrib_raytracing.bas -o example.prg
 xvic --memory 24k example.prg

In order to compile and run the example, you need to have the Speccy emulator, and in particular that the speccy executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.zx contrib_raytracing.bas -o example.tap
 Speccy example.tap
 
 # Windows 
 ugbc.zx.exe contrib_raytracing.bas -o example.tap
 Speccy example.tap

In order to compile and run the example, you need to have the openMsx or the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.msx1 contrib_raytracing.bas -o example.rom
 openmsx -cart example.rom
 
 # Windows 
 ugbc.msx1.exe contrib_raytracing.bas -o example.rom
 openmsx -cart example.rom

 # Linux 
 ugbc.msx1 contrib_raytracing.bas -o example.rom
 bluemsx example.rom
 
 # Windows 
 ugbc.msx1.exe contrib_raytracing.bas -o example.rom
 bluemsx example.rom

In order to compile and run the example, you need to have the openMsx or the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.coleco contrib_raytracing.bas -o example.rom
 openmsx -machine \"COL - ColecoVision\" -cart example.rom
 
 # Windows 
 ugbc.coleco.exe contrib_raytracing.bas -o example.rom
 bluemsx -machine \"COL - ColecoVision\" example.rom

 # Linux 
 ugbc.coleco contrib_raytracing.bas -o example.rom
 bluemsx /machine \"COL - ColecoVision\" /rom1 example.rom
 
 # Windows 
 ugbc.coleco.exe contrib_raytracing.bas -o example.rom
 bluemsx  /machine \"COL - ColecoVision\" /rom1 example.rom

In order to compile and run the example, you need to have the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.sc3000 contrib_raytracing.bas -o example.rom
 bluemsx /machine \"SEGA - SC-3000\" /rom1 example.rom
 
 # Windows 
 ugbc.sc3000.exe contrib_raytracing.bas -o example.rom
 bluemsx  /machine \"SEGA - SC-3000\" /rom1 example.rom

In order to compile and run the example, you need to have the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.sg1000 contrib_raytracing.bas -o example.rom
 bluemsx /machine \"SEGA - SG-1000\" /rom1 example.rom
 
 # Windows 
 ugbc.sg1000.exe contrib_raytracing.bas -o example.rom
 bluemsx  /machine \"SEGA - SG-1000\" /rom1 example.rom

If you have found a problem trying to run this example, if you think there is a bug or, more simply, you would like it to be improved, open an issue for this example on GitHub. Thank you!