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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <syserr.h>
include "mwcs.h"
define LTM Memd[ltm+(($2)-1)*pdim+($1)-1]
# MW_ROTATE -- Front end to mw_translate, used to perform simple rotations
# of the logical system by specifying the rotation angle in degrees, and the
# center of rotation. Since only one rotation angle can be specified, this
# routine is useful only for 2-dim rotations (between any two axes). Note
# that the transformation is performed in double precision even though the
# rotation angle and center are specified in single precision, preserving
# the full internal precision of the Lterm.
procedure mw_rotate (mw, theta, center, axbits)
pointer mw #I pointer to MWCS descriptor
real theta #I rotation angle, degrees
real center[ARB] #I center of rotation
int axbits #I bitflags defining axes to be rotated
double d_theta
pointer sp, ltm, ltv_1, ltv_2
int axis[MAX_DIM], naxes, ax1, ax2, axmap, pdim, nelem
errchk syserr
begin
# Convert axis bitflags to axis list.
call mw_gaxlist (mw, axbits, axis, naxes)
if (naxes != 2)
call syserr (SYS_MWROT2AX)
pdim = MI_NDIM(mw)
nelem = pdim * pdim
axmap = MI_USEAXMAP(mw)
MI_USEAXMAP(mw) = NO
d_theta = theta
ax1 = axis[1]
ax2 = axis[2]
call smark (sp)
call salloc (ltm, nelem, TY_DOUBLE)
call salloc (ltv_1, pdim, TY_DOUBLE)
call salloc (ltv_2, pdim, TY_DOUBLE)
# Initialize the translation matrix and vectors.
call mw_mkidmd (Memd[ltm], pdim)
call aclrd (Memd[ltv_1], pdim)
call aclrd (Memd[ltv_2], pdim)
# Set up a 2-dim rotation between the specified axes.
LTM(ax1,ax1) = cos(d_theta)
LTM(ax2,ax1) = sin(d_theta)
LTM(ax1,ax2) = -sin(d_theta)
LTM(ax2,ax2) = cos(d_theta)
# Set the rotation center.
Memd[ltv_1+ax1-1] = center[1]
Memd[ltv_1+ax2-1] = center[2]
# Set the back translation vector.
Memd[ltv_2+ax1-1] = center[1]
Memd[ltv_2+ax2-1] = center[2]
# Perform the translation.
call mw_translated (mw, Memd[ltv_1], Memd[ltm], Memd[ltv_2], pdim)
MI_USEAXMAP(mw) = axmap
call sfree (sp)
end
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