more efficient mountain drawing

diff --git a/src/scr/cybersun.c b/src/scr/cybersun.c
index e150cab..fde29ab 100644 (file)
--- a/src/scr/cybersun.c
+++ b/src/scr/cybersun.c
@@ -39,7 +39,10 @@ static struct g3d_mesh gmesh;
 #define GMESH_SIZE             128
 static struct image gtex;
 
-static struct image mounttex;
+#define MOUNTIMG_WIDTH 512
+#define MOUNTIMG_HEIGHT        64
+static struct image mountimg;
+static int mountimg_skip[MOUNTIMG_WIDTH];
 
 static long part_start;
 
@@ -63,11 +66,24 @@ static int init(void)
        if(load_image(&gtex, "data/pgrid.png") == -1) {
                return -1;
        }
-       if(load_image(&mounttex, "data/cybmount.png") == -1) {
+       if(load_image(&mountimg, "data/cybmount.png") == -1) {
                return -1;
        }
-       assert(mounttex.width == 512);
-       assert(mounttex.height == 64);
+       assert(mountimg.width == MOUNTIMG_WIDTH);
+       assert(mountimg.height == MOUNTIMG_HEIGHT);
+
+       for(i=0; i<MOUNTIMG_WIDTH; i++) {
+               uint16_t *pptr = mountimg.pixels + i;
+               for(j=0; j<MOUNTIMG_HEIGHT; j++) {
+                       if(*pptr != 0x7e0) {
+                               mountimg_skip[i] = j;
+                               break;
+                       }
+                       pptr += MOUNTIMG_WIDTH;
+               }
+       }
+       destroy_image(&mountimg);
+       mountimg.pixels = 0;
 
        return 0;
 }
@@ -76,7 +92,6 @@ static void destroy(void)
 {
        destroy_mesh(&gmesh);
        destroy_image(&gtex);
-       destroy_image(&mounttex);
 }
 
 static void start(long trans_time)
@@ -155,47 +170,46 @@ static void draw(void)
        swap_buffers(fb_pixels);
 }
 
-/* XXX all the sptr calculations assume mounttex.width == 512 */
+/* XXX all the sptr calculations assume mountimg.width == 512 */
 static void draw_mountains(void)
 {
-       int i, j, y;
+       int i, j, horizon_y, y;
        int32_t x, xstart, xend, dx;
        uint16_t *dptr, *sptr;
 
        /* 24.8 fixed point, 512 width, 90deg arc */
-       xstart = cround64(cam_theta * (256.0 * 512.0 / 90.0));
-       xend = cround64((cam_theta + HFOV) * (256.0 * 512.0 / 90.0));
+       xstart = cround64(cam_theta * (256.0 * MOUNTIMG_WIDTH / 90.0));
+       xend = cround64((cam_theta + HFOV) * (256.0 * MOUNTIMG_WIDTH / 90.0));
        dx = (xend - xstart) / FB_WIDTH;
        x = xstart;
 
-       y = cround64(-cam_phi * (FB_HEIGHT / 45.0)) + (FB_HEIGHT / 2 - 64);
+       horizon_y = cround64(-cam_phi * (FB_HEIGHT / 45.0)) + FB_HEIGHT / 2;
+       y = horizon_y - MOUNTIMG_HEIGHT;
 
-       dptr = fb_pixels + y * FB_WIDTH;
+       if(y >= FB_HEIGHT) {
+               /* TODO draw gradient for the sky */
+               return;
+       }
+       if(horizon_y < 0) {
+               memset(fb_pixels, 0, FB_WIDTH * FB_HEIGHT * 2);
+               return;
+       }
 
        for(i=0; i<FB_WIDTH; i++) {
-               sptr = mounttex.pixels + ((x >> 8) & 0x1ff);
-
-               for(j=0; j<64; j++) {
-                       if(j + y >= FB_HEIGHT) break;
-                       if(j + y >= 0) {
-                               int32_t col = sptr[j << 9];
-                               if(col != 0x7e0) {
-                                       dptr[j * FB_WIDTH] = col;
-                               }
-                       }
+               int skip = mountimg_skip[(x >> 8) & 0x1ff];
+               int vspan = MOUNTIMG_HEIGHT - skip;
+
+               dptr = fb_pixels + (y + skip) * FB_WIDTH + i;
+
+               for(j=0; j<vspan; j++) {
+                       *dptr = 0;      /* black mountains */
+                       dptr += FB_WIDTH;
                }
-               dptr++;
 
                x += dx;
        }
 
-       y += 64;
-       if(y < 0) {
-               memset(fb_pixels, 0, FB_WIDTH * FB_HEIGHT * 2);
-       } else {
-               if(y < FB_HEIGHT) {
-                       dptr = fb_pixels + y * FB_WIDTH;
-                       memset(dptr, 0, (FB_HEIGHT - y) * FB_WIDTH * 2);
-               }
+       if(horizon_y < FB_HEIGHT) {
+               memset(fb_pixels + horizon_y * FB_WIDTH, 0, (FB_HEIGHT - horizon_y) * FB_WIDTH * 2);
        }
 }