Plotting shaded spheres

Faris_hamza · April 21, 2026, 10:33am

Hi,

How can I plot spheres with shaded colors, giving it a shadow effect on a 2D map.

PlanetGus · April 21, 2026, 1:24pm

Like this example ?

Esteban82 · April 21, 2026, 5:14pm

Or something like this?

github.com/GenericMappingTools/gmt

Add the so wished option to plot spheres in psxyz. (#8844)

master ← PS-spheres

opened 11:17PM - 21 Dec 25 UTC

joa-quim

+181 -6

They aren't really spheres but circles in 3D plots. This is mostly a Claude.a…i creation but a one that needed a lot of baby-sitting development. Claude picked -SQ for this option and I honestly couldn't think of a better alternative, though -Sq is a decorated line and -SQ has nothing to do with it. Ideas for a better syntax are welcome. The following is the summary prepared by Claude ``` ● Summary of -SQ Sphere Symbol Option Basic Syntax: -SQ<size>[c|i|p][+a<azimuth>][+e<elevation>][+f][+n] Description: The -SQ option plots a 3-D sphere symbol with diameter <size>. The sphere is rendered with a radial gradient shading from white at the light source position to the fill color (specified by -G) at the opposite side, creating a realistic 3-D appearance. Size Units: - Default unit: cm (centimeters) - Supported units: c (cm), i (inches), p (points) Modifiers: - +a - Set light source azimuth angle [default: 0°, from the right] - +e - Set light source elevation angle [default: 90°, perpendicular to viewing plane] - +f - Use flat/constant fill color (disables gradient shading) - +n - Draw outline only with no fill Fill and Outline: - Fill color: Specified by -G [default: black if not specified] - Outline: Controlled by -W (pen color, width, style) - Without -G and without +n, the sphere defaults to black fill ``` The **+a** and **+e** are not working correctly and I'm not even sure that we should have them. Opinions? A low imagination example (used in the learning work) is: ``` echo 3 3 3 | gmt plot3d -R0/6/0/6/0/6 -JX10c -JZ4c -p135/45 -SQ2c -W0.2p,red -Ba -Bz -png lixo ``` <img width="1750" height="1213" alt="lixo" src="https://github.com/user-attachments/assets/7d77cb7a-3587-439c-aed0-5a698b655a77" />