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Analog Manipulation of a 3 D Object on a 2 D CRT Display

IP.com Disclosure Number: IPCOM000092371D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 55K

Publishing Venue

IBM

Related People

Criscimagna, TN: AUTHOR

Abstract

It is of advantage in a graphic display system to be able to manipulate a two-dimensional CRT isometric display of a three-dimensional object. The CRT display is conventionally formed using digital vector endpoint data provided by a computer processing unit and appropriately applied to the deflection yoke windings of the CRT. To perform manipulation, such as rotation of a displayed object, the digital data corresponding to every endpoint of every vector used in the display is operated on by an appropriate transformation function to calculate the new digital endpoint data required for each step of the manipulation.

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Analog Manipulation of a 3 D Object on a 2 D CRT Display

It is of advantage in a graphic display system to be able to manipulate a two-dimensional CRT isometric display of a three-dimensional object. The CRT display is conventionally formed using digital vector endpoint data provided by a computer processing unit and appropriately applied to the deflection yoke windings of the CRT. To perform manipulation, such as rotation of a displayed object, the digital data corresponding to every endpoint of every vector used in the display is operated on by an appropriate transformation function to calculate the new digital endpoint data required for each step of the manipulation. Using known digital processing or binary rate multiplication techniques or both, such operations can involve considerable computer processing time and much hardware, particularly where a complex object is involved, such as a bridge having many struts and beams. The following well-known equations are involved in calculating the x, y endpoints in a two-dimensional system for a rotation about the origin of a vector in a three dimensional system from a position X, Y, Z to a new position X', Y', Z'. x = X'I(H) + Y'J(H) +Z'K(H)

y = X'I(V) + Y'J(V) +Z'K(V).

Here I(H), J(H),K(H), I(V), J(V), and K(V) are the respective direction cosines between the unit vectors I, J, and K in the X, Y, Z and X', Y', Z' systems. A rotation manipulation requires six multiplications and six additions for each x,y endpoint, which is a lengthy process using known digital or binary rate multiplication techniques.

The drawing shows an improved approach. An analog function generator technique is employed for providing the X and Y deflection yoke winding signals required for each x, y endpoint in order to obtain rotation of a two-dimensional CRT display. This approach offer...