The psl_patch() function is intended for small polygons but it doesn't fill them.

[joa-quim]

This PR fixes it.

This is what we get. Note that the -G+z is ignored but the segment headers have -Z info

makecpt -T-500/0/20 > cpt.cpt
gmt plot3d D.dat -p217.5/30 -JX15c/10c -Baf -Bza -R253/278/7.6/21.6/-400/-0 -JZ3c -Ccpt.cpt -W+z -G+z -png tri_1.png

With this PR we get the triangles filled, though we still have to set -L even though the triangles are closed.

gmt plot3d D.dat -p217.5/30 -JX15c/10c -Baf -Bza -R253/278/7.6/21.6/-400/-0 -JZ3c -Ccpt.cpt -G+z -L -png tri_2.png

D.zip

[seisman]

Blindly approve.