help converting 2D rotating affine matrix to 3D raotating

[Rick T]

Greetings All

I have a function that creates an affine matrix that works for 

2D rotation around an arbitrary point but now I would like

it to work for 3D rotations also.  The working function example is below

with it's example function:

%affine matrix rotation about a point rtaffine[theta,rpx,rpy,sigx,sigy,sigz]

%crx cry rpx rpy represent center of rotation

function [rotsig,theta,crpx,crpy,sigx,sigy,sigz] = rtaffine(theta,rpx,rpy,sigx,sigy,sigz) %format in rrtaffine[theta,rpx,rpy,sigx,sigy,sigz]

rotsig=[];

%affinematrix=[];

siga=[sigx;sigy;sigz];

r00 = cosd(theta); r01 = -sind(theta); r10 = sind(theta); r11 = cosd(theta);

affinematrix = [r00, r01, rpx(1,1) - r00*rpx(1,1) - r01*rpy(1,1);...

r10, r11, rpy(1,1) - r10*rpx(1,1) - r11*rpy(1,1);...

0, 0, 1];

rotsig=affinematrix*siga; %new affine matrix

endfunction

Example code to use with function below:

clear all, clc,clf,tic

t= linspace(0,2*pi,1000); %from 0 to 1 with 100 equal spaces between

freq=1;

y=sin(freq*(t)); %pi will change phase of angle (t+pi)

y2=sin(freq*(t)); %pi will change phase of angle (t+pi)

z = ones(size(y));

siga=[t;y;z];

siga2=[t;y2;z];

rpcalc=[t(1,size(t,2)/2),0]; %size(b,2) %will count all the rows with a 1, count all colmns with 2

rp=[t(1,size(t,2)/2),0]; %rotation point half way on x/t axis

rotsigt=[];

for theta=0:1:360

rotsig=rtaffine(theta,rp(1,1),rp(1,2),siga(1,:),siga(2,:),siga(3,:));

rotsig2=rtaffine((theta*2),rp(1,1),rp(1,2),siga(1,:),siga(2,:),siga(3,:)); 

rotsigcomb=rotsig+rotsig2;

axis([-10 15 -10 10])

plot(0,0,'g*',rp(1,1),rp(1,2),'r*',rotsig(1,:),rotsig(2,:),'b-',rotsig2(1,:),rotsig2(2,:),'r',rotsigcomb(1,:),rotsigcomb(2,:),'g')

%plot(0,0,'g*',rp(1,1),rp(1,2),'r*',rotsigcomb(1,:),rotsigcomb(2,:),rotsig2(1,:),rotsig2(2,:))

axis([-10 15 -10 10])

title(['Phase Shift is ',num2str(theta),' deg']);

grid on

pause(.001)

%rotsigt=[rotsigt(:,:),rotsig(:,:)];

end

fprintf('- Complete re-import test in %4.4fsec or %4.4fmins\n',toc,toc/60);

Any suggestions?

tia sal22