Placement of the key for 3D plots (splot) by default uses the fixed option.
Note: this is a change from gnuplot version 5.0 and earlier. fixed placement
is very similar to inside placement with one important difference. The plot
boundaries of a 3D plot change as the view point is rotated or scaled. If the
key is positioned inside these boundaries then the key also moves when the
view is changed. fixed positioning ignores changes to the view angles or
scaling; i.e. the key remains fixed in one location on the canvas as the plot
is rotated.
For 2D plots the fixed option is exactly equivalent to inside.
If splot is being used to draw contours, by default a separate key entry is
generated for each contour level with a distinct line type.
To modify this see set cntrlabel (p. ).