Three-dimensional display apparatus

Apparatus for displaying perspective images comprising:

• a pointing device movable on an actual operating plane for deriving a signal indicative of movement of the device to designated points on the operating plane;
• an electronic display having a two dimensional monoscopic display surface for displaying a perspective image of an object;
• computer means responsive to the derived signal for supplying perspective image representing signals to the electronic display for display on the two dimensional monoscopic display surface;
• the computer means including a memory, selector and performing the following operations:
• calculating projection coordinates of principal vertexes of a displayed object on the display with respect to a projection plane on the display from a viewing point of the display,
• evaluating whether surfaces of the displayed object which are determined by the principal vertexes are visible or invisible from the viewing point,
• indicating the result of the evaluation,
• the memory storing information of a position of a predetermined virtual operation plane relative to the monoscopic display surface,
• responding to the stored information of the virtual operation plane position to calculate a correspondence point on the virtual operation plane corresponding to a position of the pointing device as the pointing device moves on the actual operating plane,
• calculating the position of a first three dimensional cursor formed by a first half line which starts from the correspondence point and intersects with the virtual operation plane at a predetermined settable angle,
• calculating a second half line which starts from a settable reference point and which passes through the correspondence point, the reference point being spaced from the virtual operation plane,
• the selector selecting either the first or second calculated half lines,
• calculating an intersection point between the displayed object and the selected calculated half line,
• calculating projection coordinates of at least part of the selected calculated half line with respect to the projection plane, and
• supplying the display with a signal causing the display to indicate the calculated projection coordinates of at least part of the selected calculated half line and the calculated intersection point.