EYE WALK eye_point [[view_point] [[up_point] [size]]]

     

A sequence of these commands can be used to `walk through' the model.

eye_point = Specifies the position in model coordinates at which the eye is located. If this is the only information given then the effect will be to move the model (at the current orientation and size) so that the eye point specified is translated to the centre of the viewport.

view_point = Specifies the position in model coordinates at which the eye is looking; i.e. in conjunction with the `eye_point' it defines the line of sight.

up_point = Specifies a position in model coordinates which will be vertically above the line of sight. This determines the orientation of the model about the line of sight.

size = Specifies how much of the model fits into the viewport. The `size' is given in model space coordinates and this determines the dimension of the model that will be visible within the smaller of the viewport dimensions. This effectively allows the user to apply a scale factor if required.

OFF The command EYE WALK OFF is used to turn off the Z-plane clipping activated for the walk through. (See note 2.)

Notes:

1.

Rotations
Use of the existing relative rotation commands will allow the user to `look around' the model from any `eye_point'.

2.

Clipping
During use of the EYE WALK command, the model will be Z-clipped in the plane of the viewport at the present eye point. This can produce odd looking views if when inside the model the viewport is larger than the cavity. After using the EYE WALK command, to turn off Z-plane clipping and revert to the normal mode of operation for FEMGV , it is necessary to issue the EYE WALK OFF command. Z-plane clipping will also be turned off if an EYE FRAME or EYE ROTATE TO command is issued. Note that if perspective is on then Z-plane clipping will not be turned off until the command EYE PERSPECTIVE OFF is also given.

3.

Hidden line
Hidden line pictures may be incorrect in places. This is because the facets are only clipped when drawn; i.e. the unclipped facet is used to hide facets behind it that may in fact become partly visible when the facet is clipped. (Facets that are completely in front of the clipping plane are not included).

Examples:

1.

EYE WALK 0 0 0 0 0 50 0 1 0 20

This command will result in a view from the origin of the model, in the positive direction of the model z-axis and with the model y-axis vertically upwards. The model is scaled such that 20 units of model space fit into the smallest dimension of the viewport (i.e. the height of the viewport if it is landscape).

See also the following commands

'EYE ROTATE'