How to create custom color wheel for velocity data stored as RGB and only using R/G channels?

I have velocity field data stored in RGB format where R = angle and G = amplitude/magnitude. I am wanting to create a custom color wheel with the following:

R: [0 1] where 0.5 = 0 degrees

G: [0 1] where the values increase going from the center to edge of circle

B: unused / zero

Does anyone have any suggestions on how to go about this? I would like it to be cyclic (i.e. smooth transition in colors at -pi and pi). Thank you in advance.

Answer 1

[darova]

What about this?

[R,G] = ndgrid(0:10:360,0:1);       % polar coordinates
[X,Y] = pol2cart(R*pi/180,G);       % convefrt o cartesian
Z = sind(R/2);
pcolor(X,Y,Z)

[Mat576]

This is along the lines of what I was thinking to do but a few things:

1. This has blue colors and no red. Since B channel is always zero (unused), there should not be any colors that have a blue component.
2. If R is angle and G is magnitude, then there will be a change in hue as you move from the center point to the edge as R remains constant but G changes. This is the piece I'm struggling with the most on how to incorporate it.

[darova]

Create your own color map

[T,R] = ndgrid(0:10:360,0:5);       % polar coordinates
[X,Y] = pol2cart(T*pi/180,R);       % convefrt o cartesian
[m,n] = size(R);
[r1,g1] = ndgrid((1:m)/m,(1:n)/n);  % red and green channels

surf(X,Y,X*0,cat(3,r1,g1,r1*0))     % surf with user colormap
view(0,90)

[Mat576]

Thank you! A few small tweaks got me to what I needed:

[T,R] = ndgrid(-180:180,0:(Vmax/256):Vmax);
[X,Y] = pol2cart(T*pi/180,R);
[m,n] = size(R);
[r1,g1] = ndgrid((1:m)/m,(1:n)/n);
wheel = surf(X,Y,X*0,cat(3,r1,g1,r1*0));
axis off
wheel.EdgeColor = 'none';
view(0,90)

Now to get this plotted on the corner of the velocity-field image, haha!