Uzel by Řrřola [web]
; UZEL
%define adr(x) byte si-100h+x
org 100h ;assume ax=0 bx=0 cx=255 si=100h di=-2 bp=9??h sp=-2 dx=cs=ds=es=ss
jmp B
;subroutine: draw a 32x32 sprite to xyz
I imul bp,[bx],320
_320 equ $-2
add bp,[bx+di] ; bp = Y*320+X
X xor ax,ax
add al,[fs:bx] ;0..255
jz N
add ax,dx
shr ax,3
cmp [gs:bp+(100-16)*320+(160-16)],al
jg N
mov [gs:bp+(100-16)*320+(160-16)],al
;don't draw: we're outside of a sphere or behind something
N inc bp
add bl,8
jno X
lea bp,[byte bp+si-100h+320-32]
add bh,8
jno X
fadd dword[adr(_2PIdiv256)]
_2PIdiv256
ret
db 0Fh, 0C9h, 3Ch ;= 0.0245436926
_1_5
_R dw 2, 3FC0h
B push 0A000h
mov al,13h
_19 equ $-1 ;=19
add dh,al
mov gs,dx ; gs = cs+1300h: 8-bit z-buffer
int 10h
pop es
_7 equ $-1 ;=7
add dh,al
mov fs,dx ; fs = cs+2600h: sprite depths
pop ax ; sp=0, ax=0
;palette: white->pink->black
mov dx,3c8h
R out dx,al
mov dl,0c9h
shld ax,cx,14
out dx,al
mul cl
mov al,ah
out dx,al
loop R
;precompute sphere sprites (for speed)
;has 8x8 sub-pixel accuracy, but it's unused in this intro
Q mov ax,bx
imul ax ; dx = ah*ah
mov ax,bx
imul al ; ax = al*al
add ax,dx
sub ax,128*128-64
push ax ; ax = -(128*128-64-x*x-y*y)
fild word[di]
fchs
fsqrt
fadd st0
fistp word[di] ; 0..255
pop ax
mov [fs:bx],al ; sqrt(128*128-64-x*x-y*y); 0 if outside (8000h was stored for NaNs)
inc bx
jnz Q
mov bx,8484h
;main loop
M inc word[bx+si]
fninit
;draw a trefoil to the z-buffer (512 sprites along the parametric equation)
;takes 4x"fsincos" per sphere, no big deal
;TODO:rotate
; w = cb*y + sb*z; z = -sb*y + cb*z; y = w;
; w = ca*x + sa*z; z = -sa*x + ca*z; x = w;
mov ch,2
fldz ; {u=0}
S fld st0
fsincos ; {su cu u}
fld st2
fmul dword[adr(_1_5)]; {v=1.5*u su cu u}
fsincos ; {sv cv su cu u}
fiadd word[adr(_R)] ; {R+sv cv su cu u}
fmul st2,st0
fmulp st3,st0 ; {z=cv y=(R+sv)su x=(R+sv)cu u}
C fld st1
fld st1
fild word[bx+si] ; {t z y z y x u}
fmul dword[adr(_2PIdiv256)]
fsincos ; {st ct z y z y x u}
fmul st2,st0
fmulp st3,st0 ; {ct st*z st*y z y x u}
fmul st3,st0
fmulp st4,st0 ; {st*z st*y ct*z ct*y x u}
faddp st3,st0 ; {st*y ct*z st*z+ct*y x u}
fsubp st1,st0 ; {ct*z-st*y st*z+ct*y x u}
fild word[bx+si]
fidiv word[adr(_7)]
fsin
fimul word[adr(_7)]
fiadd word[adr(_19)] ; w = 19 + 7*sin(t/7)
fmulp st1,st0
fistp word[bx+di] ; {Y=w*(ct*z-st*y) st*z+ct*y x u}
inc di
inc di ; store Y to [bx+di] and X to [bx]
jz C
neg di
;project to screen: z has width 160 (and height too)
;TODO: z += BEAT_Z * (BEAT*t-(int)(BEAT*t));
;TODO: want subpixel accuracy!
;always on the screen - no overflow tests necessary
push si
fimul word[di] ; {baseZ=z*256 u}
fistp word[di] ; store baseZ {u}
pop dx
call I ; draw sprite to xy
;drawing done: loop over all sprites
loop S
;wait for vertical retrace start (70 fps cap)
mov dx,3DAh
V in al,dx
and al,8
jz V
;copy and clear screen
pusha
imul bx,[bx+si],321
xor si,si
W mov al,-124
xchg al,[gs:si]
add al,124
jnz Z ; empty: feedback
mov al,[es:bx+si]
shr al,1
Z not al
stosb
inc si
inc bx
loop W
popa
;ESC test, maybe end
in al,60h
cmp al,1 ; clears carry
jnz M
int 20h
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