added ClutterAngle type and fast clutter_angle_sin() function; fixed clutter_fixed to work for negative angles; added convenience macros clutter_fixex_cos and clutter_angle_cos

ChangeLog

@@ -1,3 +1,17 @@
+2007-01-16  Tomas Frydrych  <tf@openedhand.com>
+	
+	* clutter/clutter-fixed.h:
+	Added integer ClutterAngle type, protype of clutter_angle_sin and
+	convenience macros clutter_fixed_cos and clutter_angle_cos
+	* clutter/clutter-fixed.c: 
+	(clutter_fixed_sin):
+	Fixed to work for negative angles.
+	(clutter_angle_sin):
+	Fast fixed point sin function for ClutterAngle angles.
+	* clutter/clutter-alpha.c: 
+	(clutter_sin_func, clutter_sin_inc_func):
+	Changed to use clutter_angle_sin function.
+	
 2007-01-15  Tomas Frydrych  <tf@openedhand.com>
 	
 	* clutter/clutter-fixed.h: (CLUTTER_FIXED_TO_DOUBLE/FLOAT):

clutter/clutter-alpha.c

@@ -491,6 +491,40 @@ clutter_ramp_func (ClutterAlpha *alpha,
     }
 }
 
+static guint32
+sincx1024_func (ClutterAlpha *alpha, 
+		ClutterAngle  angle,
+		ClutterFixed  offset)
+{
+  ClutterTimeline *timeline;
+  gint current_frame_num, n_frames;
+  ClutterAngle x;
+  ClutterFixed sine;
+  
+  timeline = clutter_alpha_get_timeline (alpha);
+
+  current_frame_num = clutter_timeline_get_current_frame (timeline);
+  n_frames = clutter_timeline_get_n_frames (timeline);
+
+  x = angle * current_frame_num / n_frames;
+
+  /*
+   * x = x*PI - PI/angle
+   */
+  x = (x << 9) - (512 / angle);
+
+  sine = (clutter_angle_sin (x) + offset)/2;
+
+  CLUTTER_NOTE (ALPHA, "sine: %2f\n", CLUTTER_FIXED_TO_DOUBLE (sine));
+
+  return CLUTTER_FIXED_INT (sine * CLUTTER_ALPHA_MAX_ALPHA);
+}
+
+#if 0
+/*
+ * The following two functions are left in place for reference
+ * purposes.
+ */
 static guint32
 sincx_func (ClutterAlpha *alpha, 
 	    ClutterFixed  angle,
@@ -538,7 +572,7 @@ sinc_func (ClutterAlpha *alpha,
 
   return (guint32) (sine * (gdouble) CLUTTER_ALPHA_MAX_ALPHA);
 }
-
+#endif
 /**
  * clutter_sine_func:
  * @alpha: a #ClutterAlpha
@@ -558,7 +592,11 @@ clutter_sine_func (ClutterAlpha *alpha,
 #if 0
   return sinc_func (alpha, 2.0, 1.0);
 #else
-  return sincx_func (alpha, CLUTTER_INT_TO_FIXED (2), CFX_ONE);
+  /* Conversion to ClutterAngle:
+   * 
+   * 2.0 rad -> 1024*2.0/(2*PI) = 325.949
+   */
+  return sincx1024_func (alpha, 326, CFX_ONE);
 #endif
 }
 
@@ -581,6 +619,10 @@ clutter_sine_inc_func (ClutterAlpha *alpha,
 #if 0
   return sinc_func (alpha, 0.5, 1.0);
 #else
-  return sincx_func (alpha, CFX_ONE / 2, CFX_ONE);
+  /* Conversion to ClutterAngle:
+   * 
+   * 0.5 rad -> 1024*0.5/(2*PI) = 81.487
+   */
+  return sincx1024_func (alpha, 81, CFX_ONE);
 #endif
 }

clutter/clutter-fixed.c

@@ -86,7 +86,7 @@ static ClutterFixed sin_tbl [] =
 
 /**
  * clutter_fixed_sin:
- * @angle: a #ClutterAlpha
+ * @angle: a #ClutterFixed angle in radians
  *
  * Fixed point implementation of sine function
  * Return value: sine value (as fixed point).
@@ -98,6 +98,13 @@ clutter_fixed_sin (ClutterFixed angle)
 {
     int sign = 1, indx1, indx2;
     ClutterFixed low, high, d1, d2;
+
+    /* convert negative angle to positive + sign */
+    if ((int)angle < 0)
+    {
+	sign  = 1 + ~sign;
+	angle = 1 + ~angle;
+    }
     
     /* reduce to <0, 2*pi) */
     if (angle >= CFX_2PI)
@@ -109,7 +116,7 @@ clutter_fixed_sin (ClutterFixed angle)
     /* reduce to first quadrant and sign */
     if (angle > CFX_PI)
     {
-	sign = -1;
+	sign = 1 + ~sign;
 	if (angle > CFX_PI + CFX_PI_2)
 	{
 	    /* fourth qudrant */
@@ -163,3 +170,64 @@ clutter_fixed_sin (ClutterFixed angle)
     
     return angle;
 }
+
+/**
+ * clutter_angle_sin:
+ * @angle: a #ClutterAngle
+ *
+ * Fast fixed point implementation of sine function.
+ *
+ * ClutterAngle is an integer such that that 1024 represents
+ * full circle.
+ * 
+ * Return value: sine value (as fixed point).
+ *
+ * Since: 0.2
+ */
+ClutterFixed
+clutter_angle_sin (ClutterAngle angle)
+{
+    int sign = 1;
+    ClutterFixed result;
+
+    /* reduce negative angle to positive + sign */
+    if (angle < 0)
+    {
+	sign  = 1 + ~sign;
+	angle = 1 + ~angle;
+    }
+    
+    /* reduce to <0, 2*pi) */
+    angle &= 0x7ff;
+    
+    /* reduce to first quadrant and sign */
+    if (angle > 512)
+    {
+	sign = 1 + ~sign;
+	if (angle > 768)
+	{
+	    /* fourth qudrant */
+	    angle = 1024 - angle;
+	}
+	else
+	{
+	    /* third quadrant */
+	    angle -= 512;
+	}
+    }
+    else
+    {
+	if (angle > 256)
+	{
+	    /* second quadrant */
+	    angle = 512 - angle;
+	}
+    }
+
+    result = sin_tbl[angle];
+    
+    if (sign < 0)
+	result = (1 + ~result);
+    
+    return result;
+}

clutter/clutter-fixed.h

@@ -31,6 +31,7 @@
 G_BEGIN_DECLS
 
 typedef gint32 ClutterFixed;
+typedef gint32 ClutterAngle;    /* angle such that 1024 == 2*PI */
 
 #define CFX_Q      16		/* Decimal part size in bits */
 #define CFX_ONE    (1 << CFX_Q)	/* 1 */
@@ -69,6 +70,11 @@ typedef gint32 ClutterFixed;
 
 /* Fixed point math routines */
 ClutterFixed clutter_fixed_sin (ClutterFixed anx);
+ClutterFixed clutter_angle_sin (ClutterAngle angle);
+
+/* convenience macros for the cos functions */
+#define clutter_fixed_cos(x) clutter_fixed_sin((x) - CFX_PI_2)
+#define clutter_angle_cos(x) clutter_fixed_sin((x) - 256)
 
 G_END_DECLS