r_draw16.asm

Quake 2 Source code for students by Theerthan You can also download from idsoftwares.com

 sbb ecx,ecx	
 mov ds:byte ptr[4+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[5+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[6+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[7+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	


;
; start FDIV for end of next segment in flight, so it can overlap
;
 mov ecx,ds:dword ptr[counttemp]	
 cmp ecx,16	; more than one segment after this?
 ja LSetupNotLast2	; yes

 dec ecx	
 jz LFDIVInFlight2	; if only one pixel, no need to start an FDIV
 mov ds:dword ptr[spancountminus1],ecx	
 fild ds:dword ptr[spancountminus1]	

 fld ds:dword ptr[_d_zistepu]	; C(d_zistepu) | spancountminus1
 fmul st(0),st(1)	; C(d_zistepu)*scm1 | scm1
 fld ds:dword ptr[_d_tdivzstepu]	; C(d_tdivzstepu) | C(d_zistepu)*scm1 | scm1
 fmul st(0),st(2)	; C(d_tdivzstepu)*scm1 | C(d_zistepu)*scm1 | scm1
 fxch st(1)	; C(d_zistepu)*scm1 | C(d_tdivzstepu)*scm1 | scm1
 faddp st(3),st(0)	; C(d_tdivzstepu)*scm1 | scm1
 fxch st(1)	; scm1 | C(d_tdivzstepu)*scm1
 fmul ds:dword ptr[_d_sdivzstepu]	; C(d_sdivzstepu)*scm1 | C(d_tdivzstepu)*scm1
 fxch st(1)	; C(d_tdivzstepu)*scm1 | C(d_sdivzstepu)*scm1
 faddp st(3),st(0)	; C(d_sdivzstepu)*scm1
 fld ds:dword ptr[fp_64k]	; 64k | C(d_sdivzstepu)*scm1
 fxch st(1)	; C(d_sdivzstepu)*scm1 | 64k
 faddp st(4),st(0)	; 64k

 fdiv st(0),st(1)	; this is what we've gone to all this trouble to
;  overlap
 jmp LFDIVInFlight2	

 align 4	
LSetupNotLast2:	
 fadd ds:dword ptr[zi16stepu]	
 fxch st(2)	
 fadd ds:dword ptr[sdivz16stepu]	
 fxch st(2)	
 fld ds:dword ptr[tdivz16stepu]	
 faddp st(2),st(0)	
 fld ds:dword ptr[fp_64k]	
 fdiv st(0),st(1)	; z = 1/1/z
; this is what we've gone to all this trouble to
;  overlap
LFDIVInFlight2:	
 mov ds:dword ptr[counttemp],ecx	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[8+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[9+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[10+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[11+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[12+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[13+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edx,ds:dword ptr[tstep]	
 sbb ecx,ecx	
 mov ds:byte ptr[14+edi],al	
 add ebx,ebp	
 mov al,ds:byte ptr[esi]	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 add edi,16	
 mov ds:dword ptr[tfracf],edx	
 mov edx,ds:dword ptr[snext]	
 mov ds:dword ptr[sfracf],ebx	
 mov ebx,ds:dword ptr[tnext]	
 mov ds:dword ptr[s],edx	
 mov ds:dword ptr[t],ebx	

 mov ecx,ds:dword ptr[counttemp]	; retrieve count

;
; determine whether last span or not
;
 cmp ecx,16	; are there multiple segments remaining?
 mov ds:byte ptr[-1+edi],al	
 ja LNotLastSegment	; yes

;
; last segment of scan
;
LLastSegment:	

;
; advance s/z, t/z, and 1/z, and calculate s & t at end of span and steps to
; get there. The number of pixels left is variable, and we want to land on the
; last pixel, not step one past it, so we can't run into arithmetic problems
;
 test ecx,ecx	
 jz LNoSteps	; just draw the last pixel and we're done

; pick up after the FDIV that was left in flight previously


 fld st(0)	; duplicate it
 fmul st(0),st(4)	; s = s/z * z
 fxch st(1)	
 fmul st(0),st(3)	; t = t/z * z
 fxch st(1)	
 fistp ds:dword ptr[snext]	
 fistp ds:dword ptr[tnext]	

 mov al,ds:byte ptr[esi]	; load first texel in segment
 mov ebx,ds:dword ptr[_tadjust]	
 mov ds:byte ptr[edi],al	; store first pixel in segment
 mov eax,ds:dword ptr[_sadjust]	

 add eax,ds:dword ptr[snext]	
 add ebx,ds:dword ptr[tnext]	

 mov ebp,ds:dword ptr[_bbextents]	
 mov edx,ds:dword ptr[_bbextentt]	

 cmp eax,4096	
 jl LClampLow4	
 cmp eax,ebp	
 ja LClampHigh4	
LClampReentry4:	
 mov ds:dword ptr[snext],eax	

 cmp ebx,4096	
 jl LClampLow5	
 cmp ebx,edx	
 ja LClampHigh5	
LClampReentry5:	

 cmp ecx,1	; don't bother 
 je LOnlyOneStep	; if two pixels in segment, there's only one step,
;  of the segment length
 sub eax,ds:dword ptr[s]	
 sub ebx,ds:dword ptr[t]	

 add eax,eax	; convert to 15.17 format so multiply by 1.31
 add ebx,ebx	;  reciprocal yields 16.48

 imul ds:dword ptr[reciprocal_table_16-8+ecx*4]	; sstep = (snext - s) /
;  (spancount-1)
 mov ebp,edx	

 mov eax,ebx	
 imul ds:dword ptr[reciprocal_table_16-8+ecx*4]	; tstep = (tnext - t) /
;  (spancount-1)
LSetEntryvec:	
;
; set up advancetable
;
 mov ebx,ds:dword ptr[entryvec_table_16+ecx*4]	
 mov eax,edx	
 mov ds:dword ptr[jumptemp],ebx	; entry point into code for RET later
 mov ecx,ebp	
 sar edx,16	; tstep >>= 16;
 mov ebx,ds:dword ptr[_cachewidth]	
 sar ecx,16	; sstep >>= 16;
 imul edx,ebx	

 add edx,ecx	; add in sstep
; (tstep >> 16) * cachewidth + (sstep >> 16);
 mov ecx,ds:dword ptr[tfracf]	
 mov ds:dword ptr[advancetable+4],edx	; advance base in t
 add edx,ebx	; ((tstep >> 16) + 1) * cachewidth +
;  (sstep >> 16);
 shl ebp,16	; left-justify sstep fractional part
 mov ebx,ds:dword ptr[sfracf]	
 shl eax,16	; left-justify tstep fractional part
 mov ds:dword ptr[advancetable],edx	; advance extra in t

 mov ds:dword ptr[tstep],eax	
 mov edx,ecx	
 add edx,eax	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	

 jmp dword ptr[jumptemp]	; jump to the number-of-pixels handler

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

LNoSteps:	
 mov al,ds:byte ptr[esi]	; load first texel in segment
 sub edi,15	; adjust for hardwired offset
 jmp LEndSpan	


LOnlyOneStep:	
 sub eax,ds:dword ptr[s]	
 sub ebx,ds:dword ptr[t]	
 mov ebp,eax	
 mov edx,ebx	
 jmp LSetEntryvec	

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

 public Entry2_16, Entry3_16, Entry4_16, Entry5_16	
 public Entry6_16, Entry7_16, Entry8_16, Entry9_16	
 public Entry10_16, Entry11_16, Entry12_16, Entry13_16	
 public Entry14_16, Entry15_16, Entry16_16	

Entry2_16:	
 sub edi,14	; adjust for hardwired offsets
 mov al,ds:byte ptr[esi]	
 jmp LEntry2_16	

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

Entry3_16:	
 sub edi,13	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 jmp LEntry3_16	

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

Entry4_16:	
 sub edi,12	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry4_16	

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

Entry5_16:	
 sub edi,11	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry5_16	

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

Entry6_16:	
 sub edi,10	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry6_16	

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

Entry7_16:	
 sub edi,9	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry7_16	

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

Entry8_16:	
 sub edi,8	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry8_16	

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

Entry9_16:	
 sub edi,7	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry9_16	

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

Entry10_16:	
 sub edi,6	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry10_16	

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

Entry11_16:	
 sub edi,5	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry11_16	

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

Entry12_16:	
 sub edi,4	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry12_16	

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

Entry13_16:	
 sub edi,3	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry13_16	

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

Entry14_16:	
 sub edi,2	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]	
 sbb ecx,ecx	
 add ebx,ebp	
 adc esi,ds:dword ptr[advancetable+4+ecx*4]	
 add edx,ds:dword ptr[tstep]	
 jmp LEntry14_16	

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

Entry15_16:	
 dec edi	; adjust for hardwired offsets
 add edx,eax	
 mov al,ds:byte ptr[esi]