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msm_ul/ShoulderModel/TOOLBOX_Kinematics/KINEMATICS_TOOL_ruled_surface_parameters.m
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KINEMATICS_TOOL_ruled_surface_parameters.m
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function RSDATA = KINEMATICS_TOOL_ruled_surface_parameters(IQuad)
% Function which generates a quadric data structure
%--------------------------------------------------------------------------
% Syntax :
% RSDATA = KINEMATICS_TOOL_ruled_surface_parameters(IQuad)
%--------------------------------------------------------------------------
%
% EPFL - LA - LBO SHOULDER MODEL
% Created by : David Ingram (LA - EPFL)
%
% File Description :
% This function generates a datastructure RSDATA with all the parameters
% related to the quadric-quadric intersection.
%--------------------------------------------------------------------------
% Initialise the output
RSDATA = [];
% Differentiate between the two types of intersection surfaces.
if isequal(IQuad.Type, 'Hyperbolic-Cylinder')
% Compute the parameters of the Intersection Surface
% alpha_1*(x - x0)^2 + alpha_2*(y - y0)^2 + alpha_4 = 0
alpha_1 = IQuad.Q(1,1);
alpha_2 = IQuad.Q(2,2);
x0 = -IQuad.Q(4,1)/alpha_1;
y0 = -IQuad.Q(4,2)/alpha_2;
alpha_4 = IQuad.Q(4,4) - (alpha_1*x0^2 + alpha_2*y0^2);
% Set the Parameters
RSDATA.Coef = [alpha_1; alpha_2; alpha_4];
RSDATA.Centre = [x0; y0];
RSDATA.Type = 'Hyperbolic-Cylinder';
RSDATA.Axis = IQuad.Axis;
RSDATA.IdS = IQuad.IndexSwitch;
RSDATA.S = IQuad.S;
RSDATA.T = IQuad.T;
RSDATA.Q = IQuad.Q;
RSDATA.ParamType = 1;
% Compute the normalised Parameters
RSDATA.NPa = sqrt(abs(alpha_4/alpha_1));
RSDATA.NPb = sqrt(abs(alpha_4/alpha_2));
RSDATA.NPc = [];
elseif isequal(IQuad.Type, 'Hyperbolic Paraboloid')
% Compute the parameters of the Intersection Surfac
% alpha_1*(x - x0)^2 + alpha_2*(y - y0)^2 + alpha_3*(z - z0) = 0
alpha_1 = IQuad.Q(1,1);
alpha_2 = IQuad.Q(2,2);
alpha_3 = 2*IQuad.Q(3,4);
x0 = -IQuad.Q(4,1)/alpha_1;
y0 = -IQuad.Q(4,2)/alpha_2;
z0 = (alpha_1*x0^2 + alpha_2*y0^2-IQuad.Q(4,4))/alpha_3;
% Set the Parameters
RSDATA.Coef = [alpha_1; alpha_2; alpha_3];
RSDATA.Centre = [x0; y0; z0];
RSDATA.Type = 'Hyperbolic Paraboloid';
RSDATA.Axis = IQuad.Axis;
RSDATA.IdS = IQuad.IndexSwitch;
RSDATA.S = IQuad.S;
RSDATA.T = IQuad.T;
RSDATA.Q = IQuad.Q;
% Compute the normalised Parameters
RSDATA.NPa = 1/sqrt(abs(alpha_1));
RSDATA.NPb = 1/sqrt(abs(alpha_2));
RSDATA.NPc = 1/sqrt(abs(alpha_3));
else
end
return;
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