Hello all, I have a query , I have a cone and I know its R and H . I also know the outer points of the cone .How I can get all points which lie inside the cone and describes the cone . thank you

http://uk.mathworks.com/matlabcentral/answers/257208-how-to-get-points-inside-a-cone#comment_325438

Points which are inside a cone

yogesh jain 2015-12-14

编辑：yogesh jain 2015-12-14

Thank you very much Mr. Roberson and sorry I did not check your previous answer .

yogesh jain 2015-12-14

And what if I want to get inside points of cone according to its starting and ending points ?

Walter Roberson 2015-12-14

What does it mean for a cone to have a starting point?

yogesh jain 2015-12-14

hello , starting point is where I want to place the circular part and ending point is where the conical section will end .

Walter Roberson 2015-12-14

The easiest way is to do the generalized rotation that you already said was too complicated; however if you are willing to constrain the orientations then there might be an easier way.

yogesh jain 2015-12-14

yes , you are right . but the code u provided is for general cone . How we can alter that for rotated and shifted cone ? is my question . Thank you .

Walter Roberson 2015-12-14

This code here is for the very specific case of a cone whose tip is at x = 0 and y = 0 and for which the center of the base is at (0,0,0) . To extend this to rotated and shifted cones can require the whole power of that link from earlier that worked out rotations in 3 space along an arbitrary center. Perhaps I could work out an easier way... but it is 04:40 in the morning here and I am not going to think about it until after I sleep and you have described exactly which axes of rotations are permitted for your situation. Remember, any cone anywhere in space could be described as having only been rotated and shifted. For example in your earlier question about cylinders you talked about it being rotated only around z: does that hold true for this as well? Rotate around z and then translate?

yogesh jain 2015-12-14

I am really very grateful towards your all considerations . Yes , the cone also permitted to rotate around z-dir . according to the rotation and point input by user I am placing the cone so it might be having random parameters (dependent on x,y,z and az-el only) . as I already told parameters of cone are R and H only . thank you

yogesh jain 2015-12-16

But if you really have any algorithm for getting inner points for cone which has starting and ending points please share that with me . thank you

Walter Roberson 2015-12-16

When an object is symmetric around one axis, then rotating around the axis produces a result identical to the original. Therefor your "dependent on x,y,z and az-el only" is really describing a cone at an arbitrary location and orientation in space, not a restricted case at all.

yogesh jain 2015-12-16

在 MATLAB Online 中打开

yes sir , that is true . But when I am rotating the points around any of the axis it is not showing them precisely . I used these -

 r=5 ; h=20;
x1=2 ; x2 =20 ; y1=3 ; y2 =3 ; z1=12; z2 = 12;
xvec = floor(-r+x1):ceil(r+x1);
yvec = xvec;
hvec = 0:ceil(h);
[X, Y, H] = ndgrid(xvec, yvec,0:floor(h));
r_at_H = r * (1 - H/h);
is_in_cone = abs(X) <= r & abs(Y) <= r & H <= h & sqrt(X.^2+Y.^2) <= r_at_H;
Xc = X(is_in_cone);
Yc = Y(is_in_cone);
Hc = H(is_in_cone);
Xc1=Xc+20.3;
Yc1=Yc+10.5;
Hc1=Hc+12.7;
 A(:,1)=Xc1;
A(:,2)=Yc1;
A(:,3)=Hc1;
B=ceil(A);
 theta=45;
rad=degtorad(theta);
C=B*[1,0,0 ; 0,cos(rad),sin(rad) ; 0,sin(rad),cos(rad)];         % X-plane
Xc2=C(:,1);
Yc2=C(:,2);
Hc2=C(:,3);
pointsize = 20;
scatter3(Xc2,Yc2,Hc2, pointsize, 'filled');

Thank you

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