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README - DOOM assembly code Okay, I add the DOS assembly module for the historically inclined here (may rec.games.programmer suffer). If anyone feels the urge to port these to GNU GCC; either inline or as separate modules including Makefile support, be my guest. Module tmap.S includes the inner loops for texture mapping, the interesting one being the floor/ceiling span rendering. There was another module in the source dump, fpfunc.S, that had both texture mapping and fixed point functions. It contained implementations both for i386 and M68k. For brevity, I include only the i386 fixed point stuff below. //==================================================== // tmap.S as of January 10th, 1997 //================ // // R_DrawColumn // //================ .data loopcount .long 0 pixelcount .long 0 .text .align 16 .globl _R_DrawColumn _R_DrawColumn: pushad movl ebp,[_dc_yl] movl ebx,ebp movl edi,[_ylookup+ebx*4] movl ebx,[_dc_x] addl edi,[_columnofs + ebx*4] movl eax,[_dc_yh] incl eax subl eax,ebp // pixel count movl [pixelcount],eax // save for final pixel js done // nothing to scale shrl eax,1 // double pixel count movl [loopcount],eax movl ecx,[_dc_iscale] movl eax,[_centery] subl eax,ebp imull ecx movl ebp,[_dc_texturemid] subl ebp,eax shll ebp,9 // 7 significant bits, 25 frac movl esi,[_dc_source] movl ebx,[_dc_iscale] shll ebx,9 movl eax,OFFSET patch1+2 // convice tasm to modify code... movl [eax],ebx movl eax,OFFSET patch2+2 // convice tasm to modify code... movl [eax],ebx // eax aligned colormap // ebx aligned colormap // ecx,edx scratch // esi virtual source // edi moving destination pointer // ebp frac movl ecx,ebp // begin calculating first pixel addl ebp,ebx // advance frac pointer shrl ecx,25 // finish calculation for first pixel movl edx,ebp // begin calculating second pixel addl ebp,ebx // advance frac pointer shrl edx,25 // finish calculation for second pixel movl eax,[_dc_colormap] movl ebx,eax movb al,[esi+ecx] // get first pixel movb bl,[esi+edx] // get second pixel movb al,[eax] // color translate first pixel movb bl,[ebx] // color translate second pixel testl [pixelcount],0fffffffeh jnz doubleloop // at least two pixels to map jmp checklast .align 16 doubleloop: movl ecx,ebp // begin calculating third pixel patch1: addl ebp,12345678h // advance frac pointer movb [edi],al // write first pixel shrl ecx,25 // finish calculation for third pixel movl edx,ebp // begin calculating fourth pixel patch2: addl ebp,12345678h // advance frac pointer movl [edi+SCREENWIDTH],bl // write second pixel shrl edx,25 // finish calculation for fourth pixel movb al,[esi+ecx] // get third pixel addl edi,SCREENWIDTH*2 // advance to third pixel destination movb bl,[esi+edx] // get fourth pixel decl [loopcount] // done with loop? movb al,[eax] // color translate third pixel movb bl,[ebx] // color translate fourth pixel jnz doubleloop // check for final pixel checklast: testl [pixelcount],1 jz done movb [edi],al // write final pixel done: popad ret //================ // // R_DrawSpan // // Horizontal texture mapping // //================ .align 16 .globl _R_DrawSpan _R_DrawSpan: pushad // // find loop count // movl eax,[_ds_x2] incl eax subl eax,[_ds_x1] // pixel count movl [pixelcount],eax // save for final pixel js hdone // nothing to scale shrl eax,1 // double pixel count movl [loopcount],eax // // build composite position // movl ebp,[_ds_xfrac] shll ebp,10 andl ebp,0ffff0000h movl eax,[_ds_yfrac] shrl eax,6 andl eax,0ffffh orl ebp,eax movl esi,[_ds_source] // // calculate screen dest // movl edi,[_ds_y] movl edi,[_ylookup+edi*4] movl eax,[_ds_x1] addl edi,[_columnofs+eax*4] // // build composite step // movl ebx,[_ds_xstep] shll ebx,10 andl ebx,0ffff0000h movl eax,[_ds_ystep] shrl eax,6 andl eax,0ffffh orl ebx,eax movl eax,OFFSET hpatch1+2 // convice tasm to modify code... movl [eax],ebx movl eax,OFFSET hpatch2+2 // convice tasm to modify code... movl [eax],ebx // eax aligned colormap // ebx aligned colormap // ecx,edx scratch // esi virtual source // edi moving destination pointer // ebp frac shldl ecx,ebp,22 // begin calculating third pixel (y units) shldl ecx,ebp,6 // begin calculating third pixel (x units) addl ebp,ebx // advance frac pointer andl ecx,4095 // finish calculation for third pixel shldl edx,ebp,22 // begin calculating fourth pixel (y units) shldl edx,ebp,6 // begin calculating fourth pixel (x units) addl ebp,ebx // advance frac pointer andl edx,4095 // finish calculation for fourth pixel movl eax,[_ds_colormap] movl ebx,eax movb al,[esi+ecx] // get first pixel movb bl,[esi+edx] // get second pixel movb al,[eax] // color translate first pixel movb bl,[ebx] // color translate second pixel testl [pixelcount],0fffffffeh jnz hdoubleloop // at least two pixels to map jmp hchecklast .align 16 hdoubleloop: shldl ecx,ebp,22 // begin calculating third pixel (y units) shldl ecx,ebp,6 // begin calculating third pixel (x units) hpatch1: addl ebp,12345678h // advance frac pointer movb [edi],al // write first pixel andl ecx,4095 // finish calculation for third pixel shldl edx,ebp,22 // begin calculating fourth pixel (y units) shldl edx,ebp,6 // begin calculating fourth pixel (x units) hpatch2: addl ebp,12345678h // advance frac pointer movb [edi+1],bl // write second pixel andl edx,4095 // finish calculation for fourth pixel movb al,[esi+ecx] // get third pixel addl edi,2 // advance to third pixel destination movb bl,[esi+edx] // get fourth pixel decl [loopcount] // done with loop? movb al,[eax] // color translate third pixel movb bl,[ebx] // color translate fourth pixel jnz hdoubleloop // check for final pixel hchecklast: testl [pixelcount],1 jz hdone movb [edi],al // write final pixel hdone: popad ret //==================================================== // fpfunc.S as of January 10th, 1997 (parts) #ifdef i386 .text .align 4 .globl _FixedMul _FixedMul: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax imull 12(%ebp) shrdl $16,%edx,%eax popl %ebp ret .align 4 .globl _FixedDiv2 _FixedDiv2: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax cdq shldl $16,%eax,%edx sall $16,%eax idivl 12(%ebp) popl %ebp ret #endif
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