nuclear@0: /*
nuclear@0: 256-color 3D graphics hack for real-mode DOS.
nuclear@0: Copyright (C) 2011  John Tsiombikas <nuclear@member.fsf.org>
nuclear@0: 
nuclear@0: This program is free software: you can redistribute it and/or modify
nuclear@0: it under the terms of the GNU General Public License as published by
nuclear@0: the Free Software Foundation, either version 3 of the License, or
nuclear@0: (at your option) any later version.
nuclear@0: 
nuclear@0: This program is distributed in the hope that it will be useful,
nuclear@0: but WITHOUT ANY WARRANTY; without even the implied warranty of
nuclear@0: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
nuclear@0: GNU General Public License for more details.
nuclear@0: 
nuclear@0: You should have received a copy of the GNU General Public License
nuclear@0: along with this program.  If not, see <http://www.gnu.org/licenses/>.
nuclear@0: */
nuclear@0: static void SCAN_EDGE(struct vertex *v0, struct vertex *v1)
nuclear@0: {
nuclear@0: 	int i, start, end;
nuclear@0: 	float dx, dy, dfdx;
nuclear@0: #ifdef INTERP_DEPTH
nuclear@0: 	float z, dz, dfdz;
nuclear@0: #endif
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 	float e, de, dfde;
nuclear@0: #endif
nuclear@0: 	float x, y;
nuclear@0: 	struct vertex *edge;
nuclear@0: 
nuclear@0: 	dy = v1->pos.y - v0->pos.y;
nuclear@0: 	if(dy < 1e-6 && dy > -1e-6) {
nuclear@0: 		return;
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	dx = v1->pos.x - v0->pos.x;
nuclear@0: 	dfdx = dx / dy;
nuclear@0: 
nuclear@0: #ifdef INTERP_DEPTH
nuclear@0: 	assert(fb->zbuf);
nuclear@0: 	dz = v1->pos.z - v0->pos.z;
nuclear@0: 	dfdz = dz / dy;
nuclear@0: #endif
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 	de = v1->energy - v0->energy;
nuclear@0: 	dfde = de / dy;
nuclear@0: #endif
nuclear@0: 
nuclear@0: 	if(dy < 0.0) {
nuclear@0: 		struct vertex *tmp = v0;
nuclear@0: 		v0 = v1;
nuclear@0: 		v1 = tmp;
nuclear@0: 		edge = (st->ord == MGL_CCW) ? vright : vleft;
nuclear@0: 	} else {
nuclear@0: 		edge = (st->ord == MGL_CCW) ? vleft : vright;
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	start = (int)ROUND(v0->pos.y);
nuclear@0: 	end = (int)ROUND(v1->pos.y);
nuclear@0: 
nuclear@0: 	x = v0->pos.x;
nuclear@0: #ifdef INTERP_DEPTH
nuclear@0: 	z = v0->pos.z;
nuclear@0: #endif
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 	e = v0->energy;
nuclear@0: #endif
nuclear@0: 	for(i=start; i<end; i++) {
nuclear@0: 		edge[i].pos.x = x;
nuclear@0: 		x += dfdx;
nuclear@0: 
nuclear@0: 		edge[i].cidx = v0->cidx;
nuclear@0: #ifdef INTERP_DEPTH
nuclear@0: 		edge[i].pos.z = z;
nuclear@0: 		z += dfdz;
nuclear@0: #endif
nuclear@0: 
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 		edge[i].energy = e;
nuclear@0: 		e += dfde;
nuclear@0: #else
nuclear@0: 		edge[i].energy = v0->energy;
nuclear@0: #endif
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: static void SCAN_LINE(int y, unsigned char *sline)
nuclear@0: {
nuclear@0: 	int i, x0, x1, len, tmp, cidx;
nuclear@0: #if defined(INTERP_DEPTH) || defined(INTERP_ENERGY)
nuclear@0: 	float x, dx;
nuclear@0: #endif
nuclear@0: #ifdef INTERP_DEPTH
nuclear@0: 	float z, dz, dfdz;
nuclear@0: #endif
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 	float e, de, dfde;
nuclear@0: #endif
nuclear@0: 	struct vertex *left, *right;
nuclear@0: 
nuclear@0: 	x0 = (int)ROUND(vleft[y].pos.x);
nuclear@0: 	x1 = (int)ROUND(vright[y].pos.x);
nuclear@0: 	len = x1 - x0;
nuclear@0: 
nuclear@0: 	if(x1 < x0) {
nuclear@0: 		if(st->flags & MGL_CULL_FACE) {
nuclear@0: 			return;
nuclear@0: 		}
nuclear@0: 		tmp = x0;
nuclear@0: 		x0 = x1;
nuclear@0: 		x1 = tmp;
nuclear@0: 		len = -len;
nuclear@0: 
nuclear@0: 		left = vright;
nuclear@0: 		right = vleft;
nuclear@0: 	} else {
nuclear@0: 		left = vleft;
nuclear@0: 		right = vright;
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	if(x0 < 0) x0 = 0;
nuclear@0: 	if(x1 >= fb->width) x1 = fb->width - 1;
nuclear@0: 
nuclear@0: 	assert(len >= 0);
nuclear@0: 
nuclear@0: 	cidx = left[y].cidx;
nuclear@0: #if !defined(INTERP_DEPTH) && !defined(INTERP_ENERGY)
nuclear@0: 	/* no interpolation at all, just memset the whole scanline */
nuclear@0: 	memset(sline + x0, cidx + left[y].energy * st->col_range, len);
nuclear@0: #else
nuclear@0: 	/* otherwise do a loop and interpolate whatever needs interpolating */
nuclear@0: 	x = left[y].pos.x;
nuclear@0: 	dx = right[y].pos.x - x;
nuclear@0: 
nuclear@0: 	if(dx < 0.5 && dx > -0.5) {
nuclear@0: 		return;
nuclear@0: 	}
nuclear@0: 
nuclear@0: #ifdef INTERP_DEPTH
nuclear@0: 	z = left[y].pos.z;
nuclear@0: 	dz = right[y].pos.z - z;
nuclear@0: 	dfdz = dz / dx;
nuclear@0: #endif
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 	e = left[y].energy;
nuclear@0: 	de = right[y].energy - e;
nuclear@0: 	dfde = de / dx;
nuclear@0: #endif
nuclear@0: 
nuclear@0: 	for(i=0; i<len; i++) {
nuclear@0: #ifdef INTERP_ENERGY
nuclear@0: 		cidx = left[y].cidx + e * st->col_range;
nuclear@0: 		e += dfde;
nuclear@0: #endif
nuclear@0: 		sline[x0 + i] = cidx;
nuclear@0: 	}
nuclear@0: #endif	/* flat */
nuclear@0: }