Experimental 3D engine in Commodore BASIC 3.5 
by Georgios Patsos 20.06.2019

Introduction:
The idea for this experimental engine is from 1984, when i fist became my commodore plus/4.
Considered as experimental, because rendering different large objects may need some changes in the code.
I exclusively tested it with the Yape-emulator with full throttle (2000%) and DRIVE 8 mode in IEC level/Performance mode. 
The files are put in the IEC folder.
The programm may run on a commodore plus/4 with SD2IEC drive, but i did not tested.

How to render your own object:
 *  Create a 3d-Modell in Blender (or other 3d-Programm) with max 3.000 verts.
 *  Export it as OBJ File with no Options clicked
 *  Convert the OBJ File with converter.exe. It outputs an vertex.seq and planes.seq
 *  Run the 3dengine to load vertex.seq and planes.seq.

Files
 * converter.exe
   Usage: converter.exe 
   Converts an OBJ file (e.g from Blender) into vertex.seq and planes.seq.

 * intro.prg
   A small introduction to the programm. Needs screen.prg

 * 3dengine.pas
   The sourcecode of the 3dengine

 * 3dengine.prg
   Programm-file. Needs: vertex.seq and planes.seq

WHEN YOU SEE A '!' PRESS FOLLOWING KEYS:
                                        
L - LINES: START RENDERING              
I - INFO: DISPLAY CURRENT VALUES        
                                        
X - ROTATE X-AXIS +15 DEGREES (GX=GX+15)
Y - ROTATE Y-AXIS +15 DEGREES (GY=GY+15)
C - ROTATE Z-AXIS +15 DEGREES (GZ=GZ+15)
B - ROTATE X-AXIS -15 DEGREES (GX=GX-15)
N - ROTATE Y-AXIS -15 DEGREES (GY=GY-15)
M - ROTATE Z-AXIS -15 DEGREES (GZ=GZ-15)
                                        
W - SHIFT UP    BY 20 PIXEL (DY=DY-20)  
A - SHIFT DOWN  BY 20 PIXEL (DX=DX-20)  
D - SHIFT RIGHT BY 20 PIXEL (DX=DX+20)  
S - SHIFT LEFT  BY 20 PIXEL (DY=DY+20)  
                                        
T - SCALE UP   BY +1 (L=L+1)            
G - SCALE DOWN BY -1 (L=L-1)            
Q - PERSPECTIVE ENHANCE  BY +1 FS=FS+1  
E - PERSPECTIVE DECREASE BY -1 FS=FS-1  
                                        
EMULATOR AT FULL SPEED IS RECOMMENDED   
PRESS KEY AND LOAD '3DENGINE'