Animation improvement

I have written a code to create an animation: satellite movement around the Earth. When I run it, it works fine. However, when it is modified to be part of a code much more complex present in a Matlab GUI, the results produced changes (mainly because of the bigger number of points to plot). I also have noticed that if I use the OpenGL renderer the movement of the satellite is quicker than when the other renderers (Painters and Zbuffer) are used. I do not know if there are further possibilities to achieve an improvement in the rendering of the satellite movement. I think the key is, perhaps, changing the code that creates the actual position of the satellite ( handles.psat ) and its trajectory along the time ( handles.tray )

 handles.tray = zeros(1,Fin);
 handles.psat = line('parent',ah4,'XData',Y(1,1), 'YData',Y(1,2),...
      'ZData',Y(1,3),'Marker','o', 'MarkerSize',10,'MarkerFaceColor','b');
  ...
 while (k<Fin)
              az = az + 0.01745329252;
              set(hgrot,'Matrix',makehgtform('zrotate',az));
              handles.tray(k) = line([Y(k-1,1) Y(k,1)],[Y(k-1,2)   Y(k,2)],...
                  [Y(k-1,3) Y(k,3)],...
          'Color','red','LineWidth',3);
              set(handles.psat,'XData',Y(k,1),'YData',Y(k,2),'ZData',Y(k,3));
              pause(0.02); 
              k = k + 1;

              if (state == 1)
                  state = 0;
                  break;
              end
 end
  ...

Answer 1

[Walter Roberson]

It might be faster to code the transform yourself as a matrix multiplication rather than calling makehgtform. The array is fairly simple: http://www.siggraph.org/education/materials/HyperGraph/modeling/mod_tran/3drota.htm

           ( cos q  sin q  0  0)
  Rz (q) = (-sin q  cos q  0  0)
           ( 0        0    1  0)
           ( 0        0    0  1)

Only two trig calls needed.

[Julián Francisco]

@Walter Roberson: Thank you for your answer. However, I do not know how to rotate the points of the sphere (this is the reason why I use hgtransform. In fact, now I am thinking of using hgtransform to build the satellite continuous trajectory).

[Walter Roberson]

Use the above matrix to multiply [X(:), Y(:), Z(:), ones(numel(X),1)]

Or just strip it down to an X-Y rotation as your Z is going to stay the same.

As you are using fixed angular steps (1 degree), you could pre-calculate all of the positions and then use simple indexing.

cq = cosd(0:359);

sq = sind(0:359);

Then (mumble... bsxfun... maybe matrix multiply... mumble) and you should be able to get out the complete point list at all angles of interest.

Sorry about the (mumble), but it is quarter to 5 in the morning here and I am fading a bit.

[Julián Francisco]

@Walter Roberson: Thank you back. Excuse me for my lazy ignorance. I have just found the rotate function also can be used to rotate the sphere.