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function [out,dout]=rodrigues(in)
% RODRIGUES Transform rotation matrix into rotation vector and viceversa.
%
% Sintax: [OUT]=RODRIGUES(IN)
% If IN is a 3x3 rotation matrix then OUT is the
% corresponding 3x1 rotation vector
% if IN is a rotation 3-vector then OUT is the
% corresponding 3x3 rotation matrix
%
%%
%% Copyright (c) March 1993 -- Pietro Perona
%% California Institute of Technology
%%
%% ALL CHECKED BY JEAN-YVES BOUGUET, October 1995.
%% FOR ALL JACOBIAN MATRICES !!! LOOK AT THE TEST AT THE END !!
%% BUG when norm(om)=pi fixed -- April 6th, 1997;
%% Jean-Yves Bouguet
[m,n] = size(in);
%bigeps = 10e+4*eps;
bigeps = 10e+20*eps;
if ((m==1) & (n==3)) | ((m==3) & (n==1)) %% it is a rotation vector
theta = norm(in);
if theta < eps
R = eye(3);
%if nargout > 1,
dRdin = [0 0 0;
0 0 1;
0 -1 0;
0 0 -1;
0 0 0;
1 0 0;
0 1 0;
-1 0 0;
0 0 0];
%end;
else
if n==length(in) in=in'; end; %% make it a column vec. if necess.
%m3 = [in,theta]
dm3din = [eye(3);in'/theta];
omega = in/theta;
%m2 = [omega;theta]
dm2dm3 = [eye(3)/theta -in/theta^2; zeros(1,3) 1];
alpha = cos(theta);
beta = sin(theta);
gamma = 1-cos(theta);
omegav=[[0 -omega(3) omega(2)];[omega(3) 0 -omega(1)];[-omega(2) omega(1) 0 ]];
A = omega*omega';
%m1 = [alpha;beta;gamma;omegav;A];
dm1dm2 = zeros(21,4);
dm1dm2(1,4) = -sin(theta);
dm1dm2(2,4) = cos(theta);
dm1dm2(3,4) = sin(theta);
dm1dm2(4:12,1:3) = [0 0 0 0 0 1 0 -1 0;
0 0 -1 0 0 0 1 0 0;
0 1 0 -1 0 0 0 0 0]';
w1 = omega(1);
w2 = omega(2);
w3 = omega(3);
dm1dm2(13:21,1) = [2*w1;w2;w3;w2;0;0;w3;0;0];
dm1dm2(13: 21,2) = [0;w1;0;w1;2*w2;w3;0;w3;0];
dm1dm2(13:21,3) = [0;0;w1;0;0;w2;w1;w2;2*w3];
R = eye(3)*alpha + omegav*beta + A*gamma;
dRdm1 = zeros(9,21);
dRdm1([1 5 9],1) = ones(3,1);
dRdm1(:,2) = omegav(:);
dRdm1(:,4:12) = beta*eye(9);
dRdm1(:,3) = A(:);
dRdm1(:,13:21) = gamma*eye(9);
dRdin = dRdm1 * dm1dm2 * dm2dm3 * dm3din;
end;
out = R;
dout = dRdin;
%% it is prob. a rot matr.
elseif ((m==n) & (m==3) & (norm(in' * in - eye(3)) < bigeps)...
& (abs(det(in)-1) < bigeps))
R = in;
tr = (trace(R)-1)/2;
dtrdR = [1 0 0 0 1 0 0 0 1]/2;
theta = real(acos(tr));
if sin(theta) >= 1e-5,
dthetadtr = -1/sqrt(1-tr^2);
dthetadR = dthetadtr * dtrdR;
% var1 = [vth;theta];
vth = 1/(2*sin(theta));
dvthdtheta = -vth*cos(theta)/sin(theta);
dvar1dtheta = [dvthdtheta;1];
dvar1dR = dvar1dtheta * dthetadR;
om1 = [R(3,2)-R(2,3), R(1,3)-R(3,1), R(2,1)-R(1,2)]';
dom1dR = [0 0 0 0 0 1 0 -1 0;
0 0 -1 0 0 0 1 0 0;
0 1 0 -1 0 0 0 0 0];
% var = [om1;vth;theta];
dvardR = [dom1dR;dvar1dR];
% var2 = [om;theta];
om = vth*om1;
domdvar = [vth*eye(3) om1 zeros(3,1)];
dthetadvar = [0 0 0 0 1];
dvar2dvar = [domdvar;dthetadvar];
out = om*theta;
domegadvar2 = [theta*eye(3) om];
dout = domegadvar2 * dvar2dvar * dvardR;
else
if tr > 0; % case norm(om)=0;
out = [0 0 0]';
dout = [0 0 0 0 0 1/2 0 -1/2 0;
0 0 -1/2 0 0 0 1/2 0 0;
0 1/2 0 -1/2 0 0 0 0 0];
else % case norm(om)=pi; %% fixed April 6th
out = theta * (sqrt((diag(R)+1)/2).*[1;2*(R(1,2:3)>=0)'-1]);
%keyboard;
if nargout > 1,
fprintf(1,'WARNING!!!! Jacobian domdR undefined!!!\n');
dout = NaN*ones(3,9);
end;
end;
end;
else
error('Neither a rotation matrix nor a rotation vector were provided');
end;
return;
%% test of the Jacobians:
%%%% TEST OF dRdom:
om = randn(3,1);
dom = randn(3,1)/1000000;
[R1,dR1] = rodrigues(om);
R2 = rodrigues(om+dom);
R2a = R1 + reshape(dR1 * dom,3,3);
gain = norm(R2 - R1)/norm(R2 - R2a)
%%% TEST OF dOmdR:
om = randn(3,1);
R = rodrigues(om);
dom = randn(3,1)/10000;
dR = rodrigues(om+dom) - R;
[omc,domdR] = rodrigues(R);
[om2] = rodrigues(R+dR);
om_app = omc + domdR*dR(:);
gain = norm(om2 - omc)/norm(om2 - om_app)
%%% OTHER BUG: (FIXED NOW!!!)
omu = randn(3,1);
omu = omu/norm(omu)
om = pi*omu;
[R,dR]= rodrigues(om);
[om2] = rodrigues(R);
[om om2]
%%% NORMAL OPERATION
om = randn(3,1);
[R,dR]= rodrigues(om);
[om2] = rodrigues(R);
[om om2]
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