+
+__attribute__((noinline, target("arm"), section(".iwram")))
+static void draw_tunnel(void)
+{
+ int i, j, tx, ty, angle, depth, zoffs;
+ uint16_t pptop, ppbot;
+ uint16_t *top, *bot;
+ uint32_t tun, *tunptr;
+
+ zoffs = nframes;
+
+ top = vram[backbuf];
+ bot = vram[backbuf] + 159 * 240 / 2;
+ tunptr = tunmap;
+ for(i=0; i<80; i++) {
+ top++;
+ bot++;
+ tunptr++;
+ for(j=1; j<240/2; j++) {
+ tun = *tunptr++;
+
+ angle = tun & 0xff;
+ depth = (tun >> 8) & 0xff;
+ tx = ((angle >> 1) + zoffs) & 0x1f;
+ ty = ((depth >> 1) + zoffs) & 0x1f;
+ pptop = tex[(ty << 5) + tx];
+ tx = ((angle >> 1) - zoffs) & 0x1f;
+ ppbot = tex[(ty << 5) + tx];
+
+ angle = (tun >> 16) & 0xff;
+ depth = (tun >> 24) & 0xff;
+ tx = ((angle >> 1) + zoffs) & 0x1f;
+ ty = ((depth >> 1) + zoffs) & 0x1f;
+ pptop |= (uint16_t)tex[(ty << 5) + tx] << 8;
+ tx = ((angle >> 1) - zoffs) & 0x1f;
+ ppbot |= (uint16_t)tex[(ty << 5) + tx] << 8;
+
+ *top++ = pptop;
+ *bot++ = ppbot;
+ }
+ bot -= 240;
+ }
+}