3D display.

The way that this is activated is described in chapter 5 of the guide.

Initial position.

Initially the x axis is horizontal, the y axis is vertical and the +z axis points towards the user. It returns to this position when ‘reset’ is activated.

Rotations.

These are around the x, y and z axes that pass through the origin. One of the rotations (the first to be selected by the user) is around a body-fixed axis, while the other two rotations are around transformed axes. Remember that the rotation and translation operations are in general not commutative -for example rotating around the screen x axis by 30 and then around the y axis by 30, followed by -30 around y and -30 around x does not restore the original configuration.

Perspective.

The ‘depth’ of the perspective view is not an angle but is an empirical parameter to vary the perspective.

When it is set to zero the program changes it to 1, which very nearly removes the perspective, but beware -the shift operations are then distorted and might cause a crash. If a large scaling factor is used the perspective option should be switched off (otherwise the picture can become multiply refolded).

Shift in z.

This allows the image to be moved towards or away from the viewer. It should not be used to move the image so near the viewer that we start to see the negative end of the object, because then the x and y shifts will not work. If you want to see the negative side of the object, rotate it by 180 degrees in the x or y directions.

Illumination and light source.

A solid object is illuminated by angle and the position of the light source is chosen by the user (and note that a positive z for the light source places it in front of the screen). The light source itself appears on the screen if it is within the screen limits. The strength of illumination of a given part of an electrode depends only on the angle between the surface normal and the line to the light source -it is independent of the distance from the light source and is also not affected by the presence of other electrodes between itself and the light source.

Beware: if the light source is within the field of view and the depth parameter (see above) is made large then the source might appear to be very large if it is has a positive z.

Axes

The x,y,z axes in 3D views are coloured red,green,blue.

Slow opening.

If the 3D view does not open immediately, this could be due to the setting of the computer’s ‘hardware acceleration’. You might be able to access this in /Control panel/display/troubleshoot/. You should experiment with the setting.