AnalyzeImpl.mesa
Copyright Ó 1992 by Xerox Corporation. All rights reserved.
M. Stone February 19, 1985 11:49:25 am PST
M. Plass March 12, 1982 11:21 am
DIRECTORY
FitState,
FitStateUtils,
DynFit,
FitBasic USING [SampleHandle],
Seq USING [ComplexSequence, RealSequence, RealSequenceRec, JointSequence],
Vector,
RealFns USING [SqRt, SinDeg, TanDeg, AlmostZero, CosDeg];
AnalyzeImpl:
PROGRAM
IMPORTS FitState, DynFit, FitStateUtils
EXPORTS Analyze = {
DeltaCurvature:
PUBLIC PROC[state: FitState.Handle, tol:
REAL, dynFilterTol:
REAL ¬ 0] = {
Finds knots by finding change in curvature greater than tol. If dynFilterTol>0 then use Filters.Dynfilter to select samples for curvature computations.
sa: Seq.ComplexSequence ¬ FitState.CurrentSamples[state];
closed: BOOLEAN ¬ FitState.GetClosed[state];
cpts: DynFit.Segments;
IF dynFilterTol>0
THEN
[segments: cpts] ¬ DynFit.FitSegments[sa, closed, dynFilterTol]
ELSE {
cpts ¬ NEW[DynFit.SegmentsRec[sa.length];
FOR i: NAT IN [0..cpts.length) DO cpts[i] ¬ i; ENDLOOP;
};
curvature ¬ NEW[Seq.RealSeqRec[cpts.length]];
FOR i:
NAT
IN [0..cpts.length)
DO
curvature[i] ¬ Curvature[sa[cpts[wrap[i-1]]], sa[cpts[wrap[i]]],sa[cpts[wrap[i+1]]]];
ENDLOOP;
FitState.ResetData[state, joints];
FOR i:
NAT
IN [0..curvature.length)
DO
FitState.SetJoint[state, cpts[i]];
ENDLOOP;
};
CheckCurvature: SampleProc = {
v0: Vec ¬ Sub[sa.xy,Prev[sa].xy];
v1: Vec ¬ Sub[Next[sa].xy,sa.xy];
m0: REAL ¬ ABS[sa.s-Prev[sa].s];
m1: REAL ¬ ABS[Next[sa].s-sa.s];
x: REAL ¬ Dot[v0,v1];
y: REAL ¬ Cross[v0,v1];
sa.value ¬ RealFns.ArcTanDeg[y,x];
sa.value ¬ .5*sa.value/(m0+m1);
};
this is angle/m0+m1/2 in radians
CCurveAngle: SampleProc = {
v0: Vec ¬ Sub[sa.xy,Prev[sa].xy];
v1: Vec ¬ Sub[Next[sa].xy,sa.xy];
m0: REAL ¬ ABS[sa.s-Prev[sa].s];
m1: REAL ¬ ABS[Next[sa].s-sa.s];
x: REAL ¬ Dot[v0,v1];
y: REAL ¬ Cross[v0,v1];
sa.value ¬ RealFns.ArcTan[y,x];
sa.value ¬ .5*sa.value/(m0+m1);
};
FindCircleCenter:
PROCEDURE[p0,p1,p2:Vector.Vec]
RETURNS [o:Vector.Vec,valid:
BOOLEAN]=
{d1,d2:Vec;
d20,d21,det:REAL;
x20,y20,x21,y21,x22,y22:REAL;
eps:REAL¬0.001;
d1¬Mul[Sub[p0,p1],2];
d2¬Mul[Sub[p1,p2],2];
x20¬p0.x*p0.x; y20¬p0.y*p0.y;
x21¬p1.x*p1.x; y21¬p1.y*p1.y;
x22¬p2.x*p2.x; y22¬p2.y*p2.y;
d20¬x20-x21+y20-y21;
d21¬x21-x22+y21-y22;
det¬Det[Matrix[d1.x,d1.y,d2.x,d2.y]];
IF ABS [det] < eps THEN
{RETURN[Vec[0,0],FALSE]} ELSE
{o.x¬(d20*d2.y-d21*d1.y)/det; o.y¬(d1.x*d21-d2.x*d20)/det;
RETURN[o,TRUE];};
};
}.