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CATMULL_SHIFT equ 16

fill_Z_buffer:

	mov	eax,0x70000000

	mov	edi,Z_buffer

	mov	ecx,SIZE_X*SIZE_Y

	rep	stosd

ret

flat_triangle_z:

;  procedure drawing triangle with Z cordinate interpolation ------

;  (Catmull  alghoritm)--------------------------------------------

;  ----------------in - eax - x1 shl 16 + y1 ----------------------

;  -------------------- ebx - x2 shl 16 + y2 ----------------------

;  -------------------- ecx - x3 shl 16 + y3 ----------------------

;  -------------------- edx - color 0x00RRGGBB --------------------

;  -------------------- esi - pointer to Z-buffer -----------------

;  -------------------- edi - pointer to screen buffer-------------

;  -------------------- stack : z coordinates

;  -------------------- Z-buffer : each z variable as dword

;  -------------------- (Z coor. as word) shl CATMULL_SHIFT

.z1	equ word[ebp+4]

.z2	equ word[ebp+6]    ; each z coordinate as word integer

.z3	equ word[ebp+8]

.col	equ dword[ebp-4]

.x1	equ word[ebp-6]

.y1	equ word[ebp-8]

.x2	equ word[ebp-10]

.y2	equ word[ebp-12]

.x3	equ word[ebp-14]

.y3	equ word[ebp-16]

.dx12	equ dword[ebp-20]

.dz12	equ dword[ebp-24]

.dx13	equ dword[ebp-28]

.dz13	equ dword[ebp-32]

.dx23	equ dword[ebp-36]

.dz23	equ dword[ebp-40]

.zz1	equ dword[ebp-44]

.zz2	equ dword[ebp-48]

	mov	ebp,esp

	push	edx	       ; store edx in variable .col

      .sort2:

	cmp	ax,bx

	jle	.sort1

	xchg	eax,ebx

	mov	dx,.z1

	xchg	dx,.z2

	mov	.z1,dx

      .sort1:

	cmp	bx,cx

	jle	.sort3

	xchg	ebx,ecx

	mov	dx,.z2

	xchg	dx,.z3

	mov	.z2,dx

	jmp	.sort2

      .sort3:

	push	eax	       ; store triangle coordinates in user friendly variables

	push	ebx

	push	ecx

	 mov	  edx,80008000h  ; eax,ebx,ecx are ANDd together into edx which means that

	 and	  edx,ebx	 ; if *all* of them are negative a sign flag is raised

	 and	  edx,ecx

	 and	  edx,eax

	 test	  edx,80008000h  ; Check both X&Y at once

	 jne	  .ft_loop2_end

       ;  cmp      ax,SIZE_Y

       ;  jle      @f

       ;  cmp      bx,SIZE_Y

       ;  jle      @f

       ;  cmp      cx,SIZE_Y

       ;  jge      @f

       ;  ror      eax,16

       ;  ror      ebx,16

       ;  ror      ecx,16

       ;  cmp      ax,SIZE_X

       ;  jle      @f

       ;  cmp      bx,SIZE_X

       ;  jle      @f

       ;  cmp      cx,SIZE_X

       ;  jle      @f

       ;  jmp      .ft_loop2_end

       ;@@:

	sub	esp,32

	mov	bx,.y2	     ; calc delta 12

	sub	bx,.y1

	jnz	.ft_dx12_make

	mov	.dx12,0

	mov	.dz12,0

	jmp	.ft_dx12_done

   .ft_dx12_make:

	mov	ax,.x2

	sub	ax,.x1

	cwde

	movsx	ebx,bx

	shl	eax,ROUND

	cdq

	idiv	ebx

	mov	.dx12,eax

	mov	ax,.z2

	sub	ax,.z1

	cwde

	shl	eax,CATMULL_SHIFT

	cdq

	idiv	ebx

	mov	.dz12,eax

  .ft_dx12_done:

	mov	bx,.y3	     ; calc delta 13

	sub	bx,.y1

	jnz	.ft_dx13_make

	mov	.dx13,0

	mov	.dz13,0

	jmp	.ft_dx13_done

   .ft_dx13_make:

	mov	ax,.x3

	sub	ax,.x1

	cwde

	movsx	ebx,bx

	shl	eax,ROUND

	cdq

	idiv	ebx

	mov	.dx13,eax

	mov	ax,.z3

	sub	ax,.z1

	cwde

	shl	eax,CATMULL_SHIFT

	cdq

	idiv	ebx

	mov	.dz13,eax

    .ft_dx13_done:

	mov	bx,.y3	     ; calc delta 23

	sub	bx,.y2

	jnz	.gt_dx23_make

	mov	.dx23,0

	mov	.dz23,0

	jmp	.gt_dx23_done

   .gt_dx23_make:

	mov	ax,.x3

	sub	ax,.x2

	cwde

	movsx	ebx,bx

	shl	eax,ROUND

	cdq

	idiv	ebx

	mov	.dx23,eax

	mov	ax,.z3

	sub	ax,.z2

	cwde

	shl	eax,CATMULL_SHIFT

	cdq

	idiv	ebx

	mov	.dz23,eax

    .gt_dx23_done:

	movsx	edx,.z1

	shl	edx,CATMULL_SHIFT

	mov	.zz1,edx

	mov	.zz2,edx

	movsx	eax,.x1

	shl	eax,ROUND    ; eax - x1

	mov	ebx,eax      ; ebx - x2

	mov	cx,.y1

	cmp	cx,.y2

	jge	.ft_loop1_end

     .ft_loop1:

	pushad

	push	.col

	push	cx	    ; y

	sar	ebx,ROUND

	push	bx	    ; x2

	sar	eax,ROUND

	push	ax	    ; x1

	push	.zz2	    ; z2 shl CATMULL_SHIFT

	push	.zz1	    ; z1 shl CATMULL_SHIFT

	call	flat_line_z

	popad

	add	eax,.dx13

	add	ebx,.dx12

	mov	edx,.dz13

	add	.zz1,edx

	mov	edx,.dz12

	add	.zz2,edx

	inc	cx

	cmp	cx,.y2

	jl	.ft_loop1

    .ft_loop1_end:

	movsx	edx,.z2

	shl	edx,CATMULL_SHIFT

	mov	.zz2,edx

	movsx	ebx,.x2

	shl	ebx,ROUND

	mov	cx,.y2

	cmp	cx,.y3

	jge	.ft_loop2_end

     .ft_loop2:

	pushad

	push	.col

	push	cx

	sar	ebx,ROUND

	push	bx

	sar	eax,ROUND

	push	ax	    ; x1

	push	.zz2	    ; z2 shl CATMULL_SHIFT

	push	.zz1	    ; z1 shl CATMULL_SHIFT

	call	flat_line_z

	popad

	add	eax,.dx13

	add	ebx,.dx23

	mov	edx,.dz13

	add	.zz1,edx

	mov	edx,.dz23

	add	.zz2,edx

	inc	cx

	cmp	cx,.y3

	jl	.ft_loop2

     .ft_loop2_end:

	mov esp,ebp

ret 6

flat_line_z:

;----------------

;-------------in edi - pointer to screen buffer ----------------------------------

;--------------- esi - pointer to z-buffer (each Z varible dword)-----------------

;----------stack - (each z coordinate shifted shl CATMULL_SHIFT)------------------

.z1 equ dword [ebp+4]

.z2 equ dword [ebp+8]

.x1 equ word  [ebp+12]

.x2 equ word  [ebp+14]

.y  equ word  [ebp+16]

.col equ dword [ebp+18]

.dz equ dword [ebp-4]

     mov	ebp,esp

;;     sub        esp,4

     mov	ax,.y

     or 	ax,ax

     jl 	.fl_quit

     cmp	ax,SIZE_Y-1

     jg 	.fl_quit

 ;    cmp        .x1,0

 ;    jge        .fl_ok1

 ;    cmp        .x2,0

 ;    jl         .fl_quit

 ;  .fl_ok1:

 ;    cmp        .x1,SIZE_X

 ;    jle        .fl_ok2

 ;    cmp        .x2,SIZE_X

 ;    jg         .fl_quit

 ;  .fl_ok2:

     mov	ax,.x1

     cmp	ax,.x2

     je 	.fl_quit

     jl 	.fl_ok

     xchg	ax,.x2

     mov	.x1,ax

     mov	edx,.z1

     xchg	edx,.z2

     mov	.z1,edx

   .fl_ok:

     cmp	.x1,SIZE_X-1

     jg 	.fl_quit

     cmp	.x2,0

     jle	.fl_quit

     mov	eax,.z2

     sub	eax,.z1

     cdq

     mov	bx,.x2

     sub	bx,.x1

     movsx	ebx,bx

     idiv	ebx

;;     mov        .dz,eax                ; calculated delta - shifted .dz

     push	eax

     cmp	.x1,0

     jge	@f

     movsx	ebx,.x1

     neg	ebx

     imul	ebx

     add	.z1,eax

     mov	.x1,0

    @@:

     cmp	.x2,SIZE_X

     jl 	@f

     mov	.x2,SIZE_X

    @@:

     mov	edx,SIZE_X

     movsx	eax,.y

     mul	edx		     ; edi = edi + (SIZE_X * y + x1)*3

     movsx	edx,.x1

     add	eax,edx

     push	eax

     lea	eax,[eax*3]

     add	edi,eax 	     ; esi = esi + (SIZE_X * y + x1)*4

     pop	eax

     shl	eax,2

     add	esi,eax

     mov	cx,.x2

     sub	cx,.x1

     movzx	ecx,cx

     mov	eax,.col

     mov	ebx,.z1  ; ebx : curr. z

     mov	edx,.dz

   .ddraw:

     ;pushad

     ;show

     ;popad

     cmp	ebx,dword[esi]

     jge	.skip

     stosd

     dec	edi

     mov	dword[esi],ebx

     jmp	.no_skip

   .skip:

     add	edi,3

   .no_skip:

     add	esi,4

     add	ebx,edx

     loop	.ddraw

   .fl_quit:

     mov   esp,ebp

ret 18