Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
2000-03-28
2001-05-22
Nguyen, Phu K. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
Reexamination Certificate
active
06236404
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to figure generating systems for image processors, and more particularly to a perspective projection calculation device and method for correcting geometrical parameters of a perspectively projected three-dimensional figure.
When a perspectively projected figure, for example a triangle, is shaded, linear interpolation is generally performed for each span, using the respective vertex coordinates of a perspectively projected triangle, and geometrical parameters necessary and sufficient for shading are approximately calculated for the respective points within the perspectively projected triangle.
In order to prevent reality based on perspective projection from being impaired, secondary interpolation is performed for each span, using the vertex coordinates of the perspectively projected triangle and geometrical parameters necessary and sufficient for shading are approximately calculated for the respective points within the perspectively projected triangle.
For example, JP-A-3-198172 discloses a method of calculating geometrical parameters necessary and sufficient for shading on a plane figure in a three-dimensional space without interpolation for each span, but no specified method of calculating interpolation coefficients used for the interpolation.
A known method of interpolation for each plane is disclosed in Juan Pineda: “A Parallel Algorithm for Polygon Rasterization”,
Computer Graphics
, Vol. 22, No. 4, August 1988, pp. 17-20. However, this method does not refer to processing of a perspectively projected figure.
In the above prior art, when interpolation coefficients necessary for interpolation are calculated for each span interpolation, calculations including division are required for each span. In addition, when geometrical parameters to be interpolated are different even in the interpolation for the same span, calculations including division for the interpolation coefficients are required for the respective parameters.
The effects of the perspective projection in the prior art are inaccurate and approximate.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a perspective projection calculation device which is capable of reducing the number of times of division required for shading, and rapidly making an accurate correction on perspective projection for each plane.
It is another object of the present invention to provide a perspective projection calculation method which is capable of reducing the number of times of division required for shading, and rapidly making an accurate correction on perspective projection for each plane.
In order to achieve the above objects, the present invention provides a perspective projection calculation device in an image processor for perspectively projecting a triangle defined in a three-dimensional space onto a two-dimensional space and for shading the triangle in the two-dimensional space, comprising:
at least one plane slope element coefficient calculating means for calculating a coefficient which implies a plane slope element of the triangle defined in the three-dimensional space;
at least one interpolation coefficient calculating means for calculating an interpolation coefficient from the plane slope element coefficient calculated by the plane slope element coefficient calculating means; and
at least one correcting means for making a perspective correction, using the interpolation coefficient.
The plane slope element coefficient may be used in common in all parameters to be interpolated.
An inverse matrix of a matrix of vertex coordinates of the triangle defined in the three-dimensional space may be used as the plane slope element coefficient.
The plane slope element coefficient, the interpolation coefficient and/or an interpolation expression including the interpolation coefficient may be used in common in the triangle defined in the three-dimensional space and/or in a perspectively projected triangle in a two-dimensional space.
The interpolation expression may involve only multiplication and/or addition.
The geometrical parameters may be interpolated in a three-dimensional space.
The interpolation expression may include a term involving a depth. More specifically, it may use the inverse of depth coordinates as geometrical parameters.
The interpolation expression may interpolate the geometrical parameters while maintaining the linearity thereof on a plane.
In order to achieve the above objects, the present invention provides a perspective projection calculation device in an image processor which includes at least one display, at least one frame buffer for storing an image to be displayed on the display, and at least one figure generator for generating a figure which composes the image on the frame buffer, thereby making a perspective correction on the respective pixels of the figure,
wherein coefficients necessary and sufficient for perspective projection calculation are used as an interface to the figure generator.
In order to achieve the above objects, the present invention provides a perspective projection calculation device in an image processor which includes a depth buffer which stores data on a depth from a viewpoint for a plane to be displayed and which removes a hidden surface, the image processor perspectively projecting a triangle defined in a three-dimensional space onto a two-dimensional space and shading the triangle in the two-dimensional space,
wherein the depth buffer comprises a buffer for storing a non-linear value in correspondence to the distance from the viewpoint.
The depth buffer may comprise a buffer for storing a non-linear value representing a resolution which increases toward the viewpoint in place of the depth value. More specifically, the depth buffer may comprise a buffer for storing the inverse of a depth value in place of the depth value.
In order to achieve the another object, the present invention provides a perspective projection calculation method in an image processing method for perspectively projecting a triangle defined in a three-dimensional space onto a two-dimensional space and for shading the triangle in the two-dimensional space, comprising the steps of:
calculating a coefficient which implies a plane slope element of the triangle defined in the three-dimensional space;
calculating an interpolation coefficient from the plane slope element coefficient; and
making a perspective correction, using the interpolation coefficient.
The plane slope element coefficient may be used in common in all parameters to be interpolated.
An inverse matrix of a matrix of vertex coordinates of the triangle defined in the three-dimensional space may be used as the plane slope element coefficient.
In any perspective projection calculation device, the plane slope element coefficient, the interpolation coefficient and/or an interpolation expression including the interpolation coefficient may be used in common in the triangle defined in the three-dimensional space and/or in a perspectively projected triangle in a two-dimensional space.
The interpolation expression may involve only multiplication and/or addition.
The geometrical parameters may be interpolated in a three-dimensional space.
The interpolation expression may include a term involving a depth. More specifically, the inter-polation expression may use the inverses of depth coordinates as the geometrical parameters.
The interpolation calculation expression may interpolate the geometrical parameters while maintaining the linearity thereof on a plane.
In order to achieve the another object, the present invention provides a perspective projection calculation method in an image processing method which uses a depth buffer which stores data on a depth from a viewpoint for a plane to be displayed and which removes a hidden surface, a triangle defined in a three-dimensional space being perspectively projected onto a two-dimensional space and the triangle being shaded in the two-dimensional space, comprising the step of:
storing a non-linear value in the depth buffer in corre
Iimura Ichiro
Nakatsuka Yasuhiro
Satoh Jun
Sone Takashi
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Nguyen Phu K.
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