X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;f=src%2Fpolyfill.c;fp=src%2Fpolyfill.c;h=25954297d33ec742eb8440adfd228b1399603fe2;hb=5b98299a1aa716cc17cb5f70498c8e23cac945cb;hp=0000000000000000000000000000000000000000;hpb=ca3123df6cd875b1361533020c1f4eebfe9da295;p=gba_blender

diff --git a/src/polyfill.c b/src/polyfill.c
new file mode 100644
index 0000000..2595429
--- /dev/null
+++ b/src/polyfill.c
@@ -0,0 +1,99 @@
+/*
+blender for the Gameboy Advance
+Copyright (C) 2021  John Tsiombikas <nuclear@member.fsf.org>
+
+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 3 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, see <https://www.gnu.org/licenses/>.
+*/
+#include <string.h>
+#include "polyfill.h"
+#include "debug.h"
+
+static unsigned char *fb;
+static int fbwidth, fbheight;
+static short scantab[2][160] __attribute__((section(".iwram")));
+
+void polyfill_framebuffer(unsigned char *ptr, int w, int h)
+{
+	fb = ptr;
+	fbwidth = w;
+	fbheight = h;
+}
+
+#define VNEXT(p)	(((p) == vlast) ? varr : (p) + 1)
+#define VPREV(p)	((p) == varr ? vlast : (p) - 1)
+#define VSUCC(p, side)	((side) == 0 ? VNEXT(p) : VPREV(p))
+
+void polyfill_flat(struct pvertex *varr, int vnum, unsigned char col)
+{
+	int i, line, top, bot;
+	struct pvertex *vlast, *v, *vn;
+	int32_t x, y0, y1, dx, dy, slope, fx, fy;
+	short *tab, start, len;
+	unsigned char *fbptr;
+
+	vlast = varr + vnum - 1;
+	top = fbheight;
+	bot = 0;
+
+	for(i=0; i<vnum; i++) {
+		v = varr + i;
+		vn = VNEXT(v);
+
+		if(vn->y == v->y) continue;
+
+		if(vn->y > v->y) {
+			tab = scantab[0];
+		} else {
+			tab = scantab[1];
+			v = vn;
+			vn = varr + i;
+		}
+
+		dx = vn->x - v->x;
+		dy = vn->y - v->y;
+		slope = (dx << 8) / dy;
+
+		y0 = (v->y + 0x100) & 0xffffff00;	/* start from the next scanline */
+		fy = y0 - v->y;						/* fractional part before the next scanline */
+		fx = (fy * slope) >> 8;				/* X adjust for the step to the next scanline */
+		x = v->x + fx;						/* adjust X */
+		y1 = vn->y & 0xffffff00;			/* last scanline of the edge <= vn->y */
+
+		line = y0 >> 8;
+		if(line < top) top = line;
+		if((y1 >> 8) > bot) bot = y1 >> 8;
+
+		if(line > 0) tab += line;
+
+		while(line < (y1 >> 8) && line < fbheight) {
+			if(line >= 0) {
+				int val = x < 0 ? 0 : x >> 8;
+				*tab++ = val < fbwidth ? val : fbwidth - 1;
+			}
+			x += slope;
+			line++;
+		}
+	}
+
+	fbptr = fb + top * fbwidth;
+	for(i=top; i<bot; i++) {
+		start = scantab[0][i];
+		len = scantab[1][i] - start;
+
+		if(len > 0) {
+			memset(fbptr + start, col, len);
+		}
+		fbptr += fbwidth;
+	}
+}