shithub: zelda3

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Remove atan2f

--- a/Makefile

+++ b/Makefile

@@ -7,7 +7,7 @@

 CFLAGS:=$(if $(CFLAGS),$(CFLAGS),-O2)

 CFLAGS:=${CFLAGS} $(shell sdl2-config --cflags)

-LDFLAGS:=${LDFLAGS} -lm $(shell sdl2-config --libs)

+LDFLAGS:=${LDFLAGS} $(shell sdl2-config --libs)

 .PHONY: all clean clean_obj clean_gen

--- a/main.c

+++ b/main.c

@@ -462,6 +462,26 @@

   }

 }

+// Approximates atan2(y, x) normalized to the [0,4) range

+// with a maximum error of 0.1620 degrees

+// normalized_atan(x) ~ (b x + x^2) / (1 + 2 b x + x^2)

+static float ApproximateAtan2(float y, float x) {

+  uint32 sign_mask = 0x80000000;

+  float b = 0.596227f;

+  // Extract the sign bits

+  uint32 ux_s = sign_mask & *(uint32 *)&x;

+  uint32 uy_s = sign_mask & *(uint32 *)&y;

+  // Determine the quadrant offset

+  float q = (float)((~ux_s & uy_s) >> 29 | ux_s >> 30);

+  // Calculate the arctangent in the first quadrant

+  float bxy_a = fabs(b * x * y);

+  float num = bxy_a + y * y;

+  float atan_1q = num / (x * x + bxy_a + num + 0.000001f);

+  // Translate it to the proper quadrant

+  uint32_t uatan_2q = (ux_s ^ uy_s) | *(uint32 *)&atan_1q;

+  return q + *(float *)&uatan_2q;

+}

+

 static void HandleGamepadAxisInput(int gamepad_id, int axis, int value) {

   static int last_gamepad_id, last_x, last_y;

   if (axis == SDL_CONTROLLER_AXIS_LEFTX || axis == SDL_CONTROLLER_AXIS_LEFTY) {

@@ -486,7 +506,7 @@

         1 << 6,           // 6 = left

         1 << 6 | 1 << 4,  // 7 = left, up

       };

-      int angle = (int)(atan2f(last_y, last_x) * (float)(128 / M_PI) + 0.5f);

+      uint8 angle = (uint8)(int)(ApproximateAtan2(last_y, last_x) * 64.0f + 0.5f);

       buttons = kSegmentToButtons[(uint8)(angle + 16 + 64) >> 5];

     }

     g_gamepad_buttons = buttons;