D3PLOT 22.1

OVERLAY... Controlling the Hidden-Line Overlay of Element Borders On Data Plots

OVERLAY... Controlling the hidden-line overlay of element borders on data plots

This figure shows the hidden-line overlay control panel.

This panel controls whether or not a hidden-line overlay is superimposed on plots, and its attributes (when drawn).

Overlay Display Controls whether and how element overlay is drawn. It does not affect the current attributes.
Overlay Colour Obviously sets the colour to be used. The default is white, but other standard colours can be chosen. ELEMENT colour means use the Overlay colour of each element - see the PROPS box in Properties: Controlling colour, drawing style, transparency, lighting attributes and overlay of entities.

Hidden-line overlays apply as follows:

  • Overlays affect all data plotting display modes, and also SH shaded ( GREYSCALE ) plots.
  • Their colour is normally fixed, but using the ELEMENT option, in conjunction with the PROPS panel, permits any permutation of overlay colours to be used.
  • The display of edges may be one of:
OFF No element overlay is drawn
Free edge The topological free edges are drawn
Feature edge Free and "feature" edges are drawn
All edges All element borders are drawn

The Edge Angle is the angle between adjacent facets at which an "edge" is deemed to occur. It affects both Feature edges and also smooth shading. The default of 60 degrees is satisfactory in most cases, but to obtain more edges reduce this value. Values approaching 180 degrees will eliminate edges altogether.

The effect of these various edge drawing options is shown in the four images below.

This image has no overlay at all This image has only free edge overlay, which is drawn only at the element edges at the back of the head. This image has feature line overlay with an "edge angle" of 20 degrees, showing detail around the mouth, nose and eyes.
This image shows all element borders.


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