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R8218/utils/@SphereContactPoint/SphereContactPoint.m
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SphereContactPoint.m
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classdef SphereContactPoint < handle
properties (Access = private)
sphere
anchorPoint = []
polarPoint = []
end
methods
function obj = SphereContactPoint(sphere)
obj.sphere = sphere;
end
function set.sphere(obj, value)
assert(isequal(class(value), "Sphere"), "Must be a Sphere instance");
obj.sphere = value;
end
function set.anchorPoint(obj, value)
assert(isnumeric(value) & isequal(size(value), [1 3]),...
"Must be a 1x3 numeric array")
assert(not(isequal(value, obj.sphere.center)),...
"Anchor point can't be superposed with sphere center");
obj.anchorPoint = value;
end
function set.polarPoint(obj, value)
assert(isnumeric(value) & isequal(size(value), [1 3]),...
"Must be a 1x3 numeric array")
assert(not(Vector(obj.sphere.center, value).norm <= obj.sphere.radius),...
"Polar point must be outside the sphere");
obj.polarPoint = value;
end
function setSphere(obj, sphere)
obj.sphere = sphere;
end
function setAnchorPoint(obj, point)
obj.anchorPoint = point;
end
function setPolarPoint(obj, point)
obj.polarPoint = point;
end
function output = getContactPoint(obj)
assert(not(isempty(obj.anchorPoint)), "Anchor point missing");
assert(not(isempty(obj.polarPoint)), "Polar point missing");
assert(obj.sphereIsBetweenAnchorAndPolarPoints,...
"There is no contact point");
poleToCenter = Vector(obj.polarPoint, obj.sphere.center);
anchorToCenter = Vector(obj.anchorPoint, obj.sphere.center);
sliceNormal = poleToCenter.cross(anchorToCenter);
poleToCenterPerpendicular = poleToCenter.cross(sliceNormal);
% angle at vertex sphere.center between contact point and polar point
contactPointsAngle = acos(obj.sphere.radius/poleToCenter.norm);
firstContactPoint = obj.sphere.center...
+ obj.sphere.radius*sin(contactPointsAngle)*poleToCenterPerpendicular.direction...
+ obj.sphere.radius*cos(contactPointsAngle)*(-poleToCenter.direction);
secondContactPoint = obj.sphere.center...
+ obj.sphere.radius*sin(contactPointsAngle)*(-poleToCenterPerpendicular.direction)...
+ obj.sphere.radius*cos(contactPointsAngle)*(-poleToCenter.direction);
output = obj.getContactPointClosestToAnchor(...
firstContactPoint, secondContactPoint);
end
function output = getContactPointClosestToAnchor(obj,...
firstContactPoint, secondContactPoint)
anchorToFirstContactPoint = Vector(obj.anchorPoint, firstContactPoint);
anchorToSecondContactPoint = Vector(obj.anchorPoint, secondContactPoint);
if anchorToFirstContactPoint.norm < anchorToSecondContactPoint.norm
output = firstContactPoint;
else
output = secondContactPoint;
end
end
function output = sphereIsBetweenAnchorAndPolarPoints(obj)
poleToCenter = Vector(obj.polarPoint, obj.sphere.center);
polarApertureAngle = abs(asin(obj.sphere.radius / poleToCenter.norm));
poleToAnchor = Vector(obj.polarPoint, obj.anchorPoint);
sphereCenterToAnchorAngle = angle(poleToCenter, poleToAnchor);
poleToContactPointDistance =...
sqrt(poleToCenter.norm^2 - obj.sphere.radius^2);
output = (sphereCenterToAnchorAngle < polarApertureAngle)...
& (poleToContactPointDistance < poleToAnchor.norm);
end
end
end
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