From bbc54accdd0db2f7135964024a3423009b5f571f Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Thu, 22 Apr 2021 11:39:29 +0300
Subject: [PATCH] correct tunnel curving

---
 src/gamescr.c  |   96 +++++++++++++++++++++++++++++++++++---------------------
 tools/tungen.c |    2 +-
 2 files changed, 61 insertions(+), 37 deletions(-)

diff --git a/src/gamescr.c b/src/gamescr.c
index aef4966..7da593a 100644
--- a/src/gamescr.c
+++ b/src/gamescr.c
@@ -85,59 +85,83 @@ void gamescr(void)
 __attribute__((noinline, target("arm"), section(".iwram")))
 static void draw_tunnel(void)
 {
-	int i, j, tx, ty, angle, depth, zoffs, uoffs, flip;
-	int tunsweep;
+	int i, j, tx, ty, angle, depth, zoffs, uoffs, flip, tunturn;
+	static int tunsweep;
 	uint16_t pptop, ppbot;
 	uint16_t *top, *bot;
 	uint32_t tun, *tunptr;
 
-	tunsweep = (SIN(nframes) >> 2) + 64;
-	if(tunsweep > 127) tunsweep = 127;
+	//tunsweep = SIN(nframes) >> 4;
 
-	flip = tunsweep >= 64;
+	if((bnstate & BN_RT) && tunsweep > -31) tunsweep--;
+	if((bnstate & BN_LT) && tunsweep < 31) tunsweep++;
 
-	tunsweep = (tunsweep & 0x3f);
-	if(tunsweep >= 32) tunsweep = 63 - tunsweep;
+	flip = tunsweep < 0;
+	tunturn = abs(tunsweep) & 0x1f;
 
 	zoffs = nframes;
 
-	uoffs = tunrot >> 1;
+	uoffs = flip ? -nframes : nframes;
 
 	top = vram[backbuf];
 	bot = vram[backbuf] + 159 * 240 / 2;
-	tunptr = tunmap + tunsweep * 9600;
-	if(flip) tunptr += 240/2;
-	for(i=0; i<80; i++) {
-		for(j=0; j<240/2; j++) {
-			if(flip) {
+	tunptr = tunmap + tunturn * 9600;
+
+	if(flip) {
+		tunptr += 240/2;
+		for(i=0; i<80; i++) {
+			for(j=0; j<240/2; j++) {
 				tun = *--tunptr;
 				tun = (tun >> 16) | (tun << 16);
-			} else {
-				tun = *tunptr++;
-			}
 
-			angle = tun & 0xff;
-			depth = (tun >> 8) & 0xff;
-			tx = ((angle >> 1) - uoffs) & 0x1f;
-			ty = ((depth >> 1) + zoffs) & 0x1f;
-			pptop = tex[(ty << 5) + tx];
-			tx = ~((angle >> 1) + uoffs) & 0x1f;
-			ppbot = tex[(ty << 5) + tx];
-
-			angle = (tun >> 16) & 0xff;
-			depth = (tun >> 24) & 0xff;
-			tx = ((angle >> 1) - uoffs) & 0x1f;
-			ty = ((depth >> 1) + zoffs) & 0x1f;
-			pptop |= (uint16_t)tex[(ty << 5) + tx] << 8;
-			tx = ~((angle >> 1) + uoffs) & 0x1f;
-			ppbot |= (uint16_t)tex[(ty << 5) + tx] << 8;
-
-			*top++ = pptop;
-			*bot++ = ppbot;
+				angle = tun & 0xff;
+				depth = (tun >> 8) & 0xff;
+				tx = ~((angle >> 1) - uoffs) & 0x1f;
+				ty = ((depth >> 1) + zoffs) & 0x1f;
+				pptop = tex[(ty << 5) + tx];
+				tx = ((angle >> 1) + uoffs) & 0x1f;
+				ppbot = tex[(ty << 5) + tx];
+
+				angle = (tun >> 16) & 0xff;
+				depth = (tun >> 24) & 0xff;
+				tx = ~((angle >> 1) - uoffs) & 0x1f;
+				ty = ((depth >> 1) + zoffs) & 0x1f;
+				pptop |= (uint16_t)tex[(ty << 5) + tx] << 8;
+				tx = ((angle >> 1) + uoffs) & 0x1f;
+				ppbot |= (uint16_t)tex[(ty << 5) + tx] << 8;
+
+				*top++ = pptop;
+				*bot++ = ppbot;
+			}
+			bot -= 240;
+			tunptr += 240;
 		}
-		bot -= 240;
+	} else {
+		for(i=0; i<80; i++) {
+			for(j=0; j<240/2; j++) {
+				tun = *tunptr++;
 
-		if(flip) tunptr += 240;
+				angle = tun & 0xff;
+				depth = (tun >> 8) & 0xff;
+				tx = ((angle >> 1) - uoffs) & 0x1f;
+				ty = ((depth >> 1) + zoffs) & 0x1f;
+				pptop = tex[(ty << 5) + tx];
+				tx = ~((angle >> 1) + uoffs) & 0x1f;
+				ppbot = tex[(ty << 5) + tx];
+
+				angle = (tun >> 16) & 0xff;
+				depth = (tun >> 24) & 0xff;
+				tx = ((angle >> 1) - uoffs) & 0x1f;
+				ty = ((depth >> 1) + zoffs) & 0x1f;
+				pptop |= (uint16_t)tex[(ty << 5) + tx] << 8;
+				tx = ~((angle >> 1) + uoffs) & 0x1f;
+				ppbot |= (uint16_t)tex[(ty << 5) + tx] << 8;
+
+				*top++ = pptop;
+				*bot++ = ppbot;
+			}
+			bot -= 240;
+		}
 	}
 }
 
diff --git a/tools/tungen.c b/tools/tungen.c
index 49b3f16..f480758 100644
--- a/tools/tungen.c
+++ b/tools/tungen.c
@@ -102,7 +102,7 @@ invalopt:	fprintf(stderr, "invalid argument: %s\n", argv[i]);
 			if(fabs(r - prev_r) < 0.05) continue;
 
 			for(j=0; j<UDIV; j++) {
-				float u = (float)j / (float)(UDIV - 1);
+				float u = (float)j / (float)UDIV;
 				float theta = 2.0f * u * M_PI;
 
 				int x = (int)(cos(theta) * r - z) + xsz / 2;
-- 
1.7.10.4