how to assign 3D points? i have 3D points on graph but i need to use those points as a variable in equation

i have generated a virtual 3D cube. as a result a graph is generated and on the graph, at each surface there are 4x4 points. i need to use those points as variables for an equation. can you please tell me how to assign some points that are on a graph, to a variable? this is the code

      %%Generate 3D calibration pattern: 
      %%Pw holds 32 points on two surfaces (Xw = 1 and Yw = 1) of a cube 
      %%Values are measured in meters.
      %%There are 4x4 uniformly distributed points on each surface.

      cnt = 1;

      %%plane : Xw = 1
      Pw = zeros(4,3);%preallocating Pw

      for i=0.2:0.2:0.8,%it means it starts from 0.2 gives an interval 0.2 and goes till 0.8
       for j=0.2:0.2:0.8,
         Pw(cnt,:) = [1 i j];%is the cnt-th row of pw , pw is a matrix whos cnt-th row is a row matrix, cnt is a variable that starts from 1 and after forming 
         %the row matrix, it goes on till i and j conditions are fulfilled. 
         cnt = cnt + 1;

       end
      end

      %%plane : Yw = 1

      for i=0.2:0.2:0.8,
       for j=0.2:0.2:0.8,
         Pw(cnt,:) = [i 1 j];
         cnt = cnt + 1;
       end
      end

      N = cnt;

      %%plot3(Pw(:,1), Pw(:,2), Pw(:,3), '+');

      %%Virtual camera model 

       %%Extrinsic parameters : R = RaRbRr

      gamma = 40.0*pi/180.0;
      Rr = [ [cos(gamma) -sin(gamma) 0];
             [sin(gamma) cos(gamma)  0];
             [  0          0         1]; ];

      beta = 0.0*pi/180.0;

      Rb = [ [cos(beta) 0 -sin(beta)];
             [0         1       0];
             [sin(beta) 0  cos(beta)]; ];

      alpha = -120.0*pi/180.0;
      Ra = [ [1      0                0];
             [0   cos(alpha)  -sin(alpha)];
             [0   sin(alpha)   cos(alpha)]; ];

      R = Ra*Rb*Rr;

      T = [0 0 4]';

      %%Intrinsic parameters

      f = 0.016;
      Ox = 256;
      Oy = 256;

      Sx = 0.0088/512.0;
      Sy = 0.0066/512.0;

      Fx = f/Sx;
      Fy = f/Sy;

      %%asr is the aspect ratio
      asr = Fx/Fy;

      %%Generate Image coordinates

      %%surface Xw = 1
      cnt = 1;
      Pc = zeros(16,3);
      n=length([(Ox - Fx*Pc(cnt,1)/Pc(cnt,3)) (Oy - Fy*Pc(cnt,2)/Pc(cnt,3))]);
       p=zeros(16,n);

      for cnt = 1:1:16,
         Pc(cnt,:) = (R*Pw(cnt,:)' + T)';
         p(cnt,:)  = [(Ox - Fx*Pc(cnt,1)/Pc(cnt,3)) (Oy - Fy*Pc(cnt,2)/Pc(cnt,3))];
      end
      plot(p(:,1), p(:,2), 'r+');
      axis([0 512 0 512]);
      grid;
      hold;

      %%surface Yw = 1
      for cnt = 17:1:32,
         Pc(cnt,:) = (R*Pw(cnt,:)' + T)';
         p(cnt,:)  = [(Ox - Fx*Pc(cnt,1)/Pc(cnt,3)) (Oy -   Fy*Pc(cnt,2)/Pc(cnt,3))];
        end
        plot(p(17:32,1), p(17:32,2), 'g+');
        %%plot3(Pc(:,1), Pc(:,2), Pc(:,3), '+');
        grid;

this is the graph

please open the picture in new tab to preview the graph.. thank you

Answer 1

[Walter Roberson]

You seem to already have them in your variable "Pc".

[Sat m]

so if i do, for example

x1 = Pc(1)
x2 = Pc(2)
....

then can i assign these points to variable x1, x2? please let me know

[Walter Roberson]

xvals = Pc(:,1);
yvals = Pc(:,2);
zvals = Pc(:,3);
x1 = xvals(1);
x2 = xvals(2);

etc.

[Sat m]

thank you. it worked...i can get 16 different points in 4 sets as. are these 2D points? if yes, then how can i know which are the x and y coordinates? and from there, how can i get the 3D points? please let me know

[Sat m]

okkk. thank you very much...

[Sat m]

there are 32 values for each x, y, and z.. so instead of assigning 96 values manually, i would like to write something as

for h (from 1 till 32 with a gap 1)

xdh=xvals(h);
ydh=yvals(h);
zdh=zvals(h);
end

disp(xdh);
disp(ydh);
disp(zdh);

can you tell me how to write [for h (from 1 till 32 with a gap of 1)] in matlab format? where h is just a number. i tried 1:1:32 but i suppose this format only works for array.

[Walter Roberson]

for h = 1 : 32

or

for h = 1 : 1 : 32

[Sat m]

thank you. it is working....