d_scan.c

/*
Copyright (C) 1996-1997 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
// d_scan.c
//
// Portable C scan-level rasterization code, all pixel depths.

#include "quakedef.h"
#include "d_local.h"

unsigned char	*r_turb_pbase, *r_turb_pdest;
fixed16_t		r_turb_s, r_turb_t, r_turb_sstep, r_turb_tstep;
int				*r_turb_turb;
int				r_turb_spancount;

void D_DrawTurbulent8Span (void);

// this performs a slight compression of the screen at the same time as
// the sine warp, to keep the edges from wrapping
void D_WarpScreen (void) {
	int w, h, u,v, *turb, *col, column[MAXWIDTH + 2 * AMP2];
	byte *dest, **row, *rowptr[MAXHEIGHT + 2 * AMP2];
	float wratio, hratio;

	w = r_refdef.vrect.width;
	h = r_refdef.vrect.height;

	wratio = w / (float) scr_vrect.width;
	hratio = h / (float) scr_vrect.height;

	for (v = 0; v < scr_vrect.height + AMP2 * 2; v++) {
		rowptr[v] = d_viewbuffer + (r_refdef.vrect.y * screenwidth) + (screenwidth * (int)((float) v * hratio * h / (h + AMP2 * 2)));
	}

	for (u = 0; u < scr_vrect.width + AMP2 * 2; u++) {
		column[u] = r_refdef.vrect.x + (int) ((float) u * wratio * w / (w + AMP2 * 2));
	}

	turb = intsintable + ((int) (cl.time * SPEED) & (CYCLE - 1));
	dest = vid.buffer + scr_vrect.y * vid.rowbytes + scr_vrect.x;

	for (v = 0; v < scr_vrect.height; v++, dest += vid.rowbytes) {
		col = &column[turb[v]];
		row = &rowptr[v];
		for (u = 0; u < scr_vrect.width; u += 4) {
			dest[u + 0] = row[turb[u + 0]][col[u + 0]];
			dest[u + 1] = row[turb[u + 1]][col[u + 1]];
			dest[u + 2] = row[turb[u + 2]][col[u + 2]];
			dest[u + 3] = row[turb[u + 3]][col[u + 3]];
		}
	}
}

#if	!id386

void D_DrawTurbulent8Span (void) {
	int sturb, tturb;

	do {
		sturb = ((r_turb_s + r_turb_turb[(r_turb_t >> 16) & (CYCLE - 1)]) >> 16) & 63;
		tturb = ((r_turb_t + r_turb_turb[(r_turb_s >> 16) & (CYCLE - 1)]) >> 16) & 63;
		*r_turb_pdest++ = *(r_turb_pbase + (tturb << 6) + sturb);
		r_turb_s += r_turb_sstep;
		r_turb_t += r_turb_tstep;
	} while (--r_turb_spancount > 0);
}

#endif	// !id386

void Turbulent8 (espan_t *pspan) {
	int count;
	fixed16_t snext, tnext;
	float sdivz, tdivz, zi, z, du, dv, spancountminus1, sdivz16stepu, tdivz16stepu, zi16stepu;
	
	r_turb_turb = sintable + ((int) (cl.time * SPEED) & (CYCLE - 1));

	r_turb_sstep = 0;	// keep compiler happy
	r_turb_tstep = 0;	// ditto

	r_turb_pbase = (unsigned char *)cacheblock;

	sdivz16stepu = d_sdivzstepu * 16;
	tdivz16stepu = d_tdivzstepu * 16;
	zi16stepu = d_zistepu * 16;

	do {
		r_turb_pdest = (unsigned char *) ((byte *) d_viewbuffer + (screenwidth * pspan->v) + pspan->u);

		count = pspan->count;

		// calculate the initial s/z, t/z, 1/z, s, and t and clamp
		du = (float) pspan->u;
		dv = (float) pspan->v;

		sdivz = d_sdivzorigin + dv * d_sdivzstepv + du * d_sdivzstepu;
		tdivz = d_tdivzorigin + dv * d_tdivzstepv + du * d_tdivzstepu;
		zi = d_ziorigin + dv * d_zistepv + du * d_zistepu;
		z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point

		r_turb_s = (int) (sdivz * z) + sadjust;
		r_turb_s = bound(0, r_turb_s, bbextents);

		r_turb_t = (int) (tdivz * z) + tadjust;
		r_turb_t = bound(0, r_turb_t, bbextentt);

		do {
			// calculate s and t at the far end of the span
			r_turb_spancount = min(count, 16);

			count -= r_turb_spancount;

			if (count) {
				// calculate s/z, t/z, zi->fixed s and t at far end of span,
				// calculate s and t steps across span by shifting
				sdivz += sdivz16stepu;
				tdivz += tdivz16stepu;
				zi += zi16stepu;
				z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point

				snext = (int) (sdivz * z) + sadjust;
				snext = bound(16, snext, bbextents);	// prevent round-off error on < 0 steps from from causing overstepping &
														//running off the edge of the texture

				tnext = (int) (tdivz * z) + tadjust;
				tnext = bound(16, tnext, bbextentt);    // guard against round-off error on <0 steps

				r_turb_sstep = (snext - r_turb_s) >> 4;
				r_turb_tstep = (tnext - r_turb_t) >> 4;
			} else {
				// calculate s/z, t/z, zi->fixed s and t at last pixel in span (so
				// can't step off polygon), clamp, calculate s and t steps across
				// span by division, biasing steps low so we don't run off the texture
				spancountminus1 = (float)(r_turb_spancount - 1);
				sdivz += d_sdivzstepu * spancountminus1;
				tdivz += d_tdivzstepu * spancountminus1;
				zi += d_zistepu * spancountminus1;
				z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point
				snext = (int) (sdivz * z) + sadjust;
				snext = bound(16, snext, bbextents); // prevent round-off error on < 0 steps from from causing overstepping &
													//running off the edge of the texture

				tnext = (int)(tdivz * z) + tadjust;
				tnext = bound(16, tnext, bbextentt); // guard against round-off error on < 0 steps

				if (r_turb_spancount > 1) {
					r_turb_sstep = (snext - r_turb_s) / (r_turb_spancount - 1);
					r_turb_tstep = (tnext - r_turb_t) / (r_turb_spancount - 1);
				}
			}

			r_turb_s = r_turb_s & ((CYCLE << 16) - 1);
			r_turb_t = r_turb_t & ((CYCLE << 16) - 1);

			D_DrawTurbulent8Span ();

			r_turb_s = snext;
			r_turb_t = tnext;

		} while (count > 0);

	} while ((pspan = pspan->pnext) != NULL);
}

#if	!id386

void D_DrawSpans8 (espan_t *pspan) {
	int count, spancount;
	unsigned char *pbase, *pdest;
	fixed16_t s, t, snext, tnext, sstep, tstep;
	float sdivz, tdivz, zi, z, du, dv, spancountminus1, sdivz8stepu, tdivz8stepu, zi8stepu;

	sstep = 0;	// keep compiler happy
	tstep = 0;	// ditto

	pbase = (unsigned char *)cacheblock;

	sdivz8stepu = d_sdivzstepu * 8;
	tdivz8stepu = d_tdivzstepu * 8;
	zi8stepu = d_zistepu * 8;

	do {
		pdest = (unsigned char *)((byte *)d_viewbuffer + (screenwidth * pspan->v) + pspan->u);

		count = pspan->count;

		// calculate the initial s/z, t/z, 1/z, s, and t and clamp
		du = (float) pspan->u;
		dv = (float) pspan->v;

		sdivz = d_sdivzorigin + dv*d_sdivzstepv + du*d_sdivzstepu;
		tdivz = d_tdivzorigin + dv*d_tdivzstepv + du*d_tdivzstepu;
		zi = d_ziorigin + dv*d_zistepv + du*d_zistepu;
		z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point

		s = (int) (sdivz * z) + sadjust;
		s = bound(0, s, bbextents);

		t = (int) (tdivz * z) + tadjust;
		t = bound(0, t, bbextentt);

		do {
			// calculate s and t at the far end of the span
			spancount = min(count, 8);

			count -= spancount;

			if (count) {
				// calculate s/z, t/z, zi->fixed s and t at far end of span,
				// calculate s and t steps across span by shifting
				sdivz += sdivz8stepu;
				tdivz += tdivz8stepu;
				zi += zi8stepu;
				z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point

				snext = (int) (sdivz * z) + sadjust;
				snext = bound(8, snext, bbextents); // prevent round-off error on < 0 steps from from causing overstepping &
													//running off the edge of the texture

				tnext = (int) (tdivz * z) + tadjust;
				tnext = bound(8, tnext, bbextentt);// guard against round-off error on <0 steps

				sstep = (snext - s) >> 3;
				tstep = (tnext - t) >> 3;
			} else {
				// calculate s/z, t/z, zi->fixed s and t at last pixel in span (so
				// can't step off polygon), clamp, calculate s and t steps across
				// span by division, biasing steps low so we don't run off the texture
				spancountminus1 = (float) (spancount - 1);
				sdivz += d_sdivzstepu * spancountminus1;
				tdivz += d_tdivzstepu * spancountminus1;
				zi += d_zistepu * spancountminus1;
				z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point
				snext = (int) (sdivz * z) + sadjust;
				snext = bound(8, snext, bbextents); // prevent round-off error on < 0 steps from from causing overstepping &
													//running off the edge of the texture

				tnext = (int)(tdivz * z) + tadjust;
				tnext = bound(8, tnext, bbextentt);

				if (spancount > 1) {
					sstep = (snext - s) / (spancount - 1);
					tstep = (tnext - t) / (spancount - 1);
				}
			}

			do {
				*pdest++ = *(pbase + (s >> 16) + (t >> 16) * cachewidth);
				s += sstep;
				t += tstep;
			} while (--spancount > 0);

			s = snext;
			t = tnext;

		} while (count > 0);

	} while ((pspan = pspan->pnext) != NULL);
}

#endif


#if	!id386

void D_DrawZSpans (espan_t *pspan) {
	int count, doublecount, izistep, izi;
	short *pdest;
	unsigned ltemp;
	double zi;
	float du, dv;

	// FIXME: check for clamping/range problems
	// we count on FP exceptions being turned off to avoid range problems
	izistep = (int)(d_zistepu * 0x8000 * 0x10000);

	do {
		pdest = d_pzbuffer + (d_zwidth * pspan->v) + pspan->u;

		count = pspan->count;

		// calculate the initial 1/z
		du = (float) pspan->u;
		dv = (float) pspan->v;

		zi = d_ziorigin + dv*d_zistepv + du*d_zistepu;
		// we count on FP exceptions being turned off to avoid range problems
		izi = (int) (zi * 0x8000 * 0x10000);

		if ((long) pdest & 0x02) {
			*pdest++ = (short) (izi >> 16);
			izi += izistep;
			count--;
		}

		if ((doublecount = count >> 1) > 0) {
			do {
				ltemp = izi >> 16;
				izi += izistep;
				ltemp |= izi & 0xFFFF0000;
				izi += izistep;
				*(int *)pdest = ltemp;
				pdest += 2;
			} while (--doublecount > 0);
		}

		if (count & 1)
			*pdest = (short) (izi >> 16);

	} while ((pspan = pspan->pnext) != NULL);
}

#endif