diff model/atan.c @ 0:5242703e91d3 tip

Initial checkin for AIM92 aimR8.2 (last updated May 1997).

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/model/atan.c	Fri May 20 15:19:45 2011 +0100
@@ -0,0 +1,103 @@
+/*
+    Copyright (c) Applied Psychology Unit, Medical Research Council. 1988, 1989
+    ===========================================================================
+
+    Permission to use, copy, modify, and distribute this software without fee 
+    is hereby granted for research purposes, provided that this copyright 
+    notice appears in all copies and in all supporting documentation, and that 
+    the software is not redistributed for any fee (except for a nominal shipping 
+    charge). Anyone wanting to incorporate all or part of this software in a
+    commercial product must obtain a license from the Medical Research Council.
+
+    The MRC makes no representations about the suitability of this 
+    software for any purpose.  It is provided "as is" without express or implied 
+    warranty.
+ 
+    THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 
+    ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE
+    A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY 
+    DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN 
+    AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include <stdio.h>
+#include <math.h>
+
+#include "stitch.h"
+
+#define OUTPUT_SCALE 360
+
+#ifdef TEST
+
+#define TwoPi (3.1415926535*2)
+
+
+main( argc, argv )
+int   argc ;
+char *argv[] ;
+{
+    double deg ;
+
+    printf( "hello\n" );
+
+    for( deg = 0 ; deg < TwoPi/2 ; deg += TwoPi/90001. )
+	if( (int) ( atan2( sin( deg ), cos( deg ) )/TwoPi*OUTPUT_SCALE + 0.5 ) != iatan2( (int) ( sin(deg)*1000 ), (int) ( cos(deg)*1000 ) ) )
+	    printf( " %f %d\n", atan2( sin( deg ), cos( deg ) )/TwoPi*OUTPUT_SCALE, iatan2( (int) ( sin(deg)*1000 ), (int) ( cos(deg)*1000 ) ) ) ;
+
+    for( ; deg < TwoPi ; deg += TwoPi/90001. )
+	if( (int) ( atan2( sin( deg ), cos( deg ) )/TwoPi*OUTPUT_SCALE - 0.5 ) != iatan2( (int) ( sin(deg)*1000 ), (int) ( cos(deg)*1000 ) ) )
+	    printf( " %f %d\n", atan2( sin( deg ), cos( deg ) )/TwoPi*OUTPUT_SCALE, iatan2( (int) ( sin(deg)*1000 ), (int) ( cos(deg)*1000 ) ) ) ;
+
+
+}
+
+#endif
+
+iatan2( y, x )
+int     y, x ;
+{
+    static int table_bits = 14 ;
+    static unsigned table_size ;
+    static short *atan_table = ( short * ) 0 ;
+    double two_phi ;
+    int i ;
+
+    if( atan_table == ( short * ) 0 ) {
+
+	table_size = 1 << table_bits ;
+
+	atan_table = ( short * ) stitch_malloc( sizeof ( *atan_table ) * ( table_size + 1 ), "Making atan lookup table" ) ;
+
+	two_phi = atan( 1. ) * 8. ;
+
+	for( i=0 ; i <= table_size ; i++ )
+	    atan_table[ i ] = atan( ( double ) i / ( table_size ) ) / two_phi * OUTPUT_SCALE + 0.5 ;
+    }
+
+    if( x != 0 || y != 0 )
+	if( y > 0 )
+	    if( x > 0 )
+		if(  x >  y )
+		    return(                          atan_table[ ( (  y << table_bits + ( table_size >> 1 ) ) ) /  x ] ) ;
+		else
+		    return(  ( OUTPUT_SCALE >> 2 ) - atan_table[ ( (  x << table_bits + ( table_size >> 1 ) ) ) /  y ] ) ;
+	    else
+		if( -x <  y )
+		    return(  ( OUTPUT_SCALE >> 2 ) + atan_table[ ( ( -x << table_bits + ( table_size >> 1 ) ) ) /  y ] ) ;
+		else
+		    return(  ( OUTPUT_SCALE >> 1 ) - atan_table[ ( (  y << table_bits + ( table_size >> 1 ) ) ) / -x ] ) ;
+	else
+	    if( x < 0 )
+		if( -x > -y )
+		    return( -( OUTPUT_SCALE >> 1 ) + atan_table[ ( ( -y << table_bits + ( table_size >> 1 ) ) ) / -x ] ) ;
+		else
+		    return( -( OUTPUT_SCALE >> 2 ) - atan_table[ ( ( -x << table_bits + ( table_size >> 1 ) ) ) / -y ] ) ;
+	    else
+		if(  x < -y )
+		    return( -( OUTPUT_SCALE >> 2 ) + atan_table[ ( (  x << table_bits + ( table_size >> 1 ) ) ) / -y ] ) ;
+		else
+		    return(                        - atan_table[ ( ( -y << table_bits + ( table_size >> 1 ) ) ) /  x ] ) ;
+    else
+	return( 99 ) ;
+}