decompile math_util

splat.yaml

@@ -48,7 +48,7 @@ segments:
     - [0x75F0, asm] # stage loader
     - [0x8EC0, c, crash_screen] # crash handler
     - [0x9D20, c, profiler]
-    - [0xAF00, asm] # camera code
+    - [0xAF00, c, math_util]
     - [0xB130, c, hal_libc]
     - [0xB230, c, gb_tower]
     - [0xC030, c] # extra sprites loader
@@ -331,6 +331,8 @@ segments:
     - [0x6A3B0, .data, profiler]
     - [0x6A3D0, .data, gb_tower]
     - [0x6A3E0, data, rom_data_6A3E0]
+    - [0x6A3F0, .data, math_util]
+    - [0x6FC00, data, rom_data_6FC00]
     - [0x7A180, .data, libleo/driverominit]
     - [0x7A190, data, rom_data_7A190]
     - [0x7A2A0, .data, libultra/os/initialize]

src/controller.c

@@ -1,9 +1,7 @@
 #include <ultra64.h>
 #include "controller.h"
 #include "gb_tower.h"
-
+#include "math_util.h"
-// TODO: Identify/move to header
-extern s16 func_8000A360(float, float);
 
 struct Controller gControllers[4];
 OSMesgQueue gSIEventMesgQueue;
@@ -77,7 +75,7 @@ void Cont_AdjustAnalogStick(struct Controller* controller) {
     }
 
     if (controller->stickMag > 0.0f) {
-        controller->unkE = func_8000A360(-controller->stickY, controller->stickX);
+        controller->unkE = MathUtil_Atan2s(-controller->stickY, controller->stickX);
     }
 }
 

src/math_util.c

@@ -0,0 +1,77 @@
+#include <ultra64.h>
+#include "math_util.h"
+
+// this file might be the leftovers of math_util.c from sm64/mk64.
+
+#include "trig_tables.inc.c"
+
+/**
+ * Helper function for atan2s. Does a look up of the arctangent of y/x assuming
+ * the resulting angle is in range [0, 0x2000] (1/8 of a circle).
+ */
+u16 MathUtil_Atan2Lookup(f32 y, f32 x) {
+    u16 ret;
+
+    if (x == 0) {
+        ret = gArctanTable[0];
+    } else {
+        ret = gArctanTable[(s32)(y / x * 1024 + 0.5f)];
+    }
+    return ret;
+}
+
+/**
+ * Compute the angle from (0, 0) to (x, y) as a s16. Given that terrain is in
+ * the xz-plane, this is commonly called with (z, x) to get a yaw angle.
+ */
+s16 MathUtil_Atan2s(f32 y, f32 x) {
+    u16 ret;
+
+    if (x >= 0) {
+        if (y >= 0) {
+            if (y >= x) {
+                ret = MathUtil_Atan2Lookup(x, y);
+            } else {
+                ret = 0x4000 - MathUtil_Atan2Lookup(y, x);
+            }
+        } else {
+            y = -y;
+            if (y < x) {
+                ret = 0x4000 + MathUtil_Atan2Lookup(y, x);
+            } else {
+                ret = 0x8000 - MathUtil_Atan2Lookup(x, y);
+            }
+        }
+    } else {
+        x = -x;
+        if (y < 0) {
+            y = -y;
+            if (y >= x) {
+                ret = 0x8000 + MathUtil_Atan2Lookup(x, y);
+            } else {
+                ret = 0xC000 - MathUtil_Atan2Lookup(y, x);
+            }
+        } else {
+            if (y < x) {
+                ret = 0xC000 + MathUtil_Atan2Lookup(y, x);
+            } else {
+                ret = -MathUtil_Atan2Lookup(x, y);
+            }
+        }
+    }
+    return ret;
+}
+
+/**
+ * Gets a random 16-bit value determined by the guRandom call.
+ */
+s32 MathUtil_Random16(void) {
+    return guRandom() & 0xFFFF; // would prototype this as u16, but doesnt match with other calls.
+}
+
+/**
+ * Gets a random float between 0.0 to 1.0.
+ */
+f32 MathUtil_Random_ZeroOne(void) {
+    return MathUtil_Random16() / 65536.0f;
+}

src/math_util.h

@@ -0,0 +1,13 @@
+#ifndef _MATH_UTIL_H_
+#define _MATH_UTIL_H_
+
+extern f32 gSineTable[];
+extern f32 gCosineTable[0x1000];
+extern s16 gArctanTable[0x401];
+
+u16 MathUtil_Atan2Lookup(f32 y, f32 x);
+s16 MathUtil_Atan2s(f32 y, f32 x);
+s32 MathUtil_Random16(void);
+f32 MathUtil_Random_ZeroOne(void);
+
+#endif // _MATH_UTIL_H_

tools/symbol_addrs.txt

@@ -592,4 +592,11 @@ mem_pool_alloc = 0x80002AF8;
 mem_pool_free = 0x80002BD0;
 Util_DrawMemProfiler = 0x8000310C;
 Util_Malloc = 0x80002FDC;
-Util_Free = 0x80003004;
+Util_Free = 0x80003004;
+MathUtil_Atan2Lookup = 0x8000A300;
+MathUtil_Atan2s = 0x8000A360;
+gArctanTable = 0x8006E7F0;
+gSineTable = 0x800697F0;
+gCosineTable = 0x8006A7F0;
+MathUtil_Random16 = 0x8000A4D4;
+MathUtil_Random_ZeroOne = 0x8000A4F8;