3D plot in spherical polar coordinates and also use of texture
Nikroo
Sat, 10/23/2010 - 04:43 pm
I have been struggling trying to get a 3D plot of a unit sphere that has some "bumps" on it at specific theta phi locations.
More specifically, I have r(theta,phi) and I want to plot it so that the color scheme corresponds to the r value.
So, I have the data in terms of (r, theta, phi) triplets and I have played with using the parametric form of 3D surface plot first by plotting a smooth sphere (that is z^2=+/-(1- X^2+y^2), where I get x and y using theta, phi as regularly spaced parameters). This works fine, but the plot colors are in rainbow color, for example, so although this is a unit sphere (constant r=1) , the color map is not uniform. I use "constant color" instead of rainbow, but I am not sure if that is the right way to do it.
To take the test further, then I add some noise to the x,y,z values to simulate the deviation from a perfect sphere. That's where I have stopped and decided to ask, how one get the color scheme to go with the r value when using the parametric wave plotting scheme, or if there is a better way of just plotting r vs theta phi directly?
Finally, I saw the texture video tutorial, and when I tried to implement that on a test image wrapped on my sphere , when I got to the point where I was to make a "group" by adding an object in Gizmo, the append object menu did NOT gave me the group option. Also, I figured that the the group is not really needed for wrapping the texture on the sphere, so I just tried to add texture directly (forgoing the other options added in the video to the group) again the append object menu did NOT give me the texture option either. Why am I not getting those menu option?
I am using IGOR 6.12.
Thanks
AN
IP 6.12 is old. You should upgrade to the latest version by visiting our web site.
You have several options in coloring the sphere. The simplest is to assign a colortable to the parametric surface and then click on the Details button next to the color table menu and select a Color Table Span corresponding to your radius. A more flexible approach is to provide your own color wave as in the Gizmo Sphere demo (File Menu->Example Experiments->Visualization->GizmoSphere). You can then assign RGBA colors on a vertex by vertex basis.
I do not recommend using textures for this purpose mostly because it is more complicated, sometimes slightly less accurate and requires advanced understanding of OpenGL. If you still want to pursue that approach contact me directly and I will send you the relevant information.
A.G.
WaveMetrics, Inc.
October 24, 2010 at 03:23 am - Permalink
I am new to the exchange. How do I contact you directly? In the meantime I will look to see if I can find the instructions on the site.
Also, I downloaded 6.2, but the missing menu items do not appear in this version either in the append object pop up.
October 24, 2010 at 07:32 am - Permalink
Send an email to support@wavemetrics.com and request it be forwarded to A.G.
For the Group object to show up, type this command in Igor's command line:
--Jim Prouty
Software Engineer, WaveMetrics, Inc.
October 24, 2010 at 11:49 pm - Permalink