Group lines by color in the legend of a 3D plot

Hi guys,

I'm struggling with the display of the legend in a 3D plot. I have a 3D plot of lines with some similar properties (color, line width, etc.) and what I basically want is to display the legend based on color only.

The thing is that I'm not familiar with the "set", "get" and "gca" functions so I'm completely lost when it comes to "parent" and "children" relations ... I've never understood what this gca function does or what is a handle, so I'm sure this is where the problem comes from.

1) When I do this, I have the correct display of colors and line width I want, but the legend is not correct. The legend shows each and every line that has been plotted while I wanted to group them by color.

 for ind=1:ind_max
    set(gca,'ColorOrder',colorOrder)

    plot3(X1(:,ind),Y1(:,ind),Z1(:,ind))
    hold on
    plot3(X2(:,ind),Y2(:,ind),Z2(:,ind),'LineWidth',3)
    plot3(X3(:,ind),Y3(:,ind),Z3(:,ind),'LineWidth',5)
 end
 legend

2) Looking in the manual, and some forum answer, I found something about the 'NextPlot' attribute. I tried to give it a shot but it was even worse. When I do this, the plot is not a 3D plot but a 2D plot. How come ?

 for ind=1:ind_max
    set(gca,'ColorOrder',colorOrder)
    set(gca,'NextPlot','replacechildren')

    plot3(X1(:,ind),Y1(:,ind),Z1(:,ind))
    hold on
    plot3(X2(:,ind),Y2(:,ind),Z2(:,ind),'LineWidth',3)
    plot3(X3(:,ind),Y3(:,ind),Z3(:,ind),'LineWidth',5)
 end
 legend

3) When I do this, the plot is 3D plot but it the previous lines are erased at each iteration of the "for" loop

 for ind=1:ind_max
    set(gca,'ColorOrder',colorOrder)

    plot3(X1(:,ind),Y1(:,ind),Z1(:,ind))
    hold on
    plot3(X2(:,ind),Y2(:,ind),Z2(:,ind),'LineWidth',3)
    plot3(X3(:,ind),Y3(:,ind),Z3(:,ind),'LineWidth',5)
    set(gca,'NextPlot','replacechildren')
 end
  legend

What am I doing wrong ? Thanks a lot.

Cheers,