Removed division in displacement inner loop

Stole Optimus' FPS counter as an extern

diff --git a/src/grise.c b/src/grise.c
index 543b51e..1a1cebf 100644 (file)
--- a/src/grise.c
+++ b/src/grise.c
@@ -26,6 +26,8 @@ static RLEBitmap *rleEncode(RLEBitmap *b, unsigned char *pixels, unsigned int w,
 
 static void updatePropeller(float t);
 
+extern void drawFps(unsigned short *vram);
+
 #define BG_FILENAME "data/grise.png"
 #define GROBJ_01_FILENAME "data/grobj_01.png"
 
@@ -97,7 +99,6 @@ struct screen *grise_screen(void)
        return &scr;
 }
 
-
 static int init(void)
 {
        unsigned char *tmpBitmap;
@@ -167,6 +168,9 @@ static void draw(void)
        int i = 0;
        short *dispScanline;
        int d;
+       int accum = 0;
+       int md, sc;
+       int scrolledIndex;
 
        lastFrameDuration = (time_msec - lastFrameTime) / 1000.0f;
        lastFrameTime = time_msec;
@@ -203,8 +207,19 @@ static void draw(void)
        src = dst + BB_SIZE; /* The pixels to be displaced are 1 scanline below */
        dispScanline = displacementMap;
        for (scanline = 0; scanline < REFLECTION_HEIGHT; scanline++) {
+
+               md = scrollModTable[scanline];
+               sc = scrollTableRounded[scanline];
+               accum = 0;
+
                for (i = 0; i < fb_width; i++) {
-                       d = dispScanline[(i + scrollTableRounded[scanline]) % scrollModTable[scanline]];
+                       /* Try to immitate modulo without the division */
+                       if (i == md) accum += md;
+                       scrolledIndex = i - accum + sc;
+                       if (scrolledIndex >= md) scrolledIndex -= md;
+
+                       /* Displace */
+                       d = dispScanline[scrolledIndex];
                        *dst++ = src[i + d];
                }
                src += backgroundW;
@@ -224,6 +239,8 @@ static void draw(void)
                dst += fb_width;
        }
 
+       drawFps(vmem_back);
+
        swap_buffers(0);
 }