System and method for shading graphic images using an accessibility factor to simulate tarnish accumulation for realistic rendering

A computer implemented method for shading graphic images for realistic rendering representative of tarnish accumulation, the method comprising the steps of:

• identifying objects forming an image;
• determining which pixels of the image are visible on a display device;
• generating an accessibility factor, said accessibility factor being a value of a radius for a largest sphere that may touch a point (X) tangentially and that does not intersect with a surface upon which the point (X) lies or any other surfaces, for each visible pixel;
• generating a blend value for each pixel using its respective accessibility factor;
• and
• shading each pixel as it is rendered on the display device by applying the blend value to image signals for the respective pixel.

A computer implemented method for improving the computational efficiency of determining an accessibility factor, said accessibility factor being a value of a radius for a largest sphere that may touch a point (X) tangentially and that does not intersect with a surface upon which the point (X) lies or any other surfaces, for a plurality of pixels to be generated on a display device, the pixels representing one or more objects on the display device, the method comprising the steps of:

• identifying a first pixel and its corresponding point and surface;
• determining the accessibility factor for the first pixel;
• creating a sloppy bound for the point corresponding to the first pixel, the sloppy bound being greater than a maximum radius (R1);
• creating a sloppy list of objects that intersect with the sloppy bound;
• retrieving a second pixel and its corresponding point and surface for which accessibility needs to be determined;
• determining whether a tangential sphere with the maximum radius R.sub.1 and positioned tangential to the point of the second pixel fits within the sloppy bound;
• and
• if the tangential sphere with the maximum radius R.sub.1 fits within the sloppy bound, then the accessibility factor is calculated by only considering the objects in the sloppy list.

An apparatus for shading graphic images for realistic rendering representative of tarnish accumulation on a display device, the apparatus comprising:

• first means for identifying objects forming an image, the first identifying means having an input and an output, the input of the first identifying means coupled to receive objects forming at least one image;
• means for determining the visible pixels of the image on the display device, the determining means having an input and an output, the input of the determining means coupled to the output of the first identifying means;
• means for generating an accessibility factor, said accessibility factor being a value of a radius for a largest sphere that may touch a point (X) tangentially and that does not intersect with a surface upon which the point (X) lies or any other surfaces, for each visible pixel, the generating means having an input and an output, the input of the generating means coupled to the output of the determining means;
• means for producing a blend value for each pixel using its respective accessibility factor, the producing means having an input and an output, the input of the producing means coupled to the output of the generating means;
• and
• means for shading each pixel as it is rendered on the display device by applying the blend value to the respective pixel, the shading means having a first input, a second input and an output, the first input of the shading means coupled to the output of the producing means, and the second input of the shading means coupled to receive the image.

A system for improving the computational efficiency of determining an accessibility factor, said accessibility factor being a value of a radius for a largest sphere that may touch a point (X) tangentially and that does not intersect with a surface upon which the point (X) lies or any other surfaces, for a plurality of pixels to be generated on a display device, the pixels representing one or more objects on the display device, the system comprising:

• means for identifying a first pixel and its corresponding point and surface;
• a first means for determining the accessibility factor for the first pixel;
• means for creating a sloppy bound for the point corresponding to the first pixel, the sloppy bound being greater than a maximum radius (R1);
• means for storing a sloppy list of objects that intersect with the sloppy bound;
• means for retrieving a next pixel and its corresponding point and surface for which accessibility needs to be determined;
• a second means for determining whether a tangential sphere with the maximum radius (R.sub.1) and positioned tangential to the point of the next pixel fits within the sloppy bound;
• and
• means for calculating the accessibility factor by only considering the objects in the sloppy list if the tangential sphere with the maximum radius (R.sub.1) fits within the sloppy bound.