doom_py/src/vizdoom/src/r_drawt.cpp [1149:1218]:
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	while (span->Length != 0)
	{
		const int length = span->Length;
		const int top = span->TopOffset;

		// calculate unclipped screen coordinates for post
		dc_yl = (sprtopscreen + spryscale * top) >> FRACBITS;
		dc_yh = (sprtopscreen + spryscale * (top + length) - FRACUNIT) >> FRACBITS;

		if (sprflipvert)
		{
			swapvalues (dc_yl, dc_yh);
		}

		if (dc_yh >= mfloorclip[dc_x])
		{
			dc_yh = mfloorclip[dc_x] - 1;
		}
		if (dc_yl < mceilingclip[dc_x])
		{
			dc_yl = mceilingclip[dc_x];
		}

		if (dc_yl <= dc_yh)
		{
			if (sprflipvert)
			{
				dc_texturefrac = (dc_yl*dc_iscale) - (top << FRACBITS)
					- FixedMul (centeryfrac, dc_iscale) - dc_texturemid;
				const fixed_t maxfrac = length << FRACBITS;
				while (dc_texturefrac >= maxfrac)
				{
					if (++dc_yl > dc_yh)
						goto nextpost;
					dc_texturefrac += dc_iscale;
				}
				fixed_t endfrac = dc_texturefrac + (dc_yh-dc_yl)*dc_iscale;
				while (endfrac < 0)
				{
					if (--dc_yh < dc_yl)
						goto nextpost;
					endfrac -= dc_iscale;
				}
			}
			else
			{
				dc_texturefrac = dc_texturemid - (top << FRACBITS)
					+ (dc_yl*dc_iscale) - FixedMul (centeryfrac-FRACUNIT, dc_iscale);
				while (dc_texturefrac < 0)
				{
					if (++dc_yl > dc_yh)
						goto nextpost;
					dc_texturefrac += dc_iscale;
				}
				fixed_t endfrac = dc_texturefrac + (dc_yh-dc_yl)*dc_iscale;
				const fixed_t maxfrac = length << FRACBITS;
				if (dc_yh < mfloorclip[dc_x]-1 && endfrac < maxfrac - dc_iscale)
				{
					dc_yh++;
				}
				else while (endfrac >= maxfrac)
				{
					if (--dc_yh < dc_yl)
						goto nextpost;
					endfrac -= dc_iscale;
				}
			}
			dc_source = column + top;
			dc_dest = ylookup[dc_yl] + dc_x + dc_destorg;
			dc_count = dc_yh - dc_yl + 1;
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doom_py/src/vizdoom/src/r_things.cpp [244:313]:
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	while (span->Length != 0)
	{
		const int length = span->Length;
		const int top = span->TopOffset;

		// calculate unclipped screen coordinates for post
		dc_yl = (sprtopscreen + spryscale * top) >> FRACBITS;
		dc_yh = (sprtopscreen + spryscale * (top + length) - FRACUNIT) >> FRACBITS;

		if (sprflipvert)
		{
			swapvalues (dc_yl, dc_yh);
		}

		if (dc_yh >= mfloorclip[dc_x])
		{
			dc_yh = mfloorclip[dc_x] - 1;
		}
		if (dc_yl < mceilingclip[dc_x])
		{
			dc_yl = mceilingclip[dc_x];
		}

		if (dc_yl <= dc_yh)
		{
			if (sprflipvert)
			{
				dc_texturefrac = (dc_yl*dc_iscale) - (top << FRACBITS)
					- FixedMul (centeryfrac, dc_iscale) - dc_texturemid;
				const fixed_t maxfrac = length << FRACBITS;
				while (dc_texturefrac >= maxfrac)
				{
					if (++dc_yl > dc_yh)
						goto nextpost;
					dc_texturefrac += dc_iscale;
				}
				fixed_t endfrac = dc_texturefrac + (dc_yh-dc_yl)*dc_iscale;
				while (endfrac < 0)
				{
					if (--dc_yh < dc_yl)
						goto nextpost;
					endfrac -= dc_iscale;
				}
			}
			else
			{
				dc_texturefrac = dc_texturemid - (top << FRACBITS)
					+ (dc_yl*dc_iscale) - FixedMul (centeryfrac-FRACUNIT, dc_iscale);
				while (dc_texturefrac < 0)
				{
					if (++dc_yl > dc_yh)
						goto nextpost;
					dc_texturefrac += dc_iscale;
				}
				fixed_t endfrac = dc_texturefrac + (dc_yh-dc_yl)*dc_iscale;
				const fixed_t maxfrac = length << FRACBITS;
				if (dc_yh < mfloorclip[dc_x]-1 && endfrac < maxfrac - dc_iscale)
				{
					dc_yh++;
				}
				else while (endfrac >= maxfrac)
				{
					if (--dc_yh < dc_yl)
						goto nextpost;
					endfrac -= dc_iscale;
				}
			}
			dc_source = column + top;
			dc_dest = ylookup[dc_yl] + dc_x + dc_destorg;
			dc_count = dc_yh - dc_yl + 1;
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