Patent ID: 8049753

Claim:
A method, executable in a computer graphics system operable to render images using an image rendering process, and to apply shading to rendered images using a shading model, wherein the computer graphics system is operable to render images by applying a shading model to geometric representations constructed from a scene description containing geometric primitives, and wherein, as a surface point P is being shaded, it is assumed to have one shading normal N s , and one geometric normal N g , the method comprising: modifying the shading normal in the region of a corner of an object in the image such that the region of the corner of the object in the image will, when shaded by using a shading model, provide to a human viewer the visual appearance of a rounded edge, the modifying comprising: interrogating the nearby region of the corner for adjacent surfaces within a radius of R of the corner, wherein R is the apparent fillet radius for the corner, the interrogating comprising querying data structures associated with the scene for adjacency information usable to find adjacent surfaces within a radius R of the corner, wherein the interrogating comprises executing a ray-casting process, the ray-casting process comprising: finding a tangent plane defined by two vectors, u and v, that arc tangential to the geometric normal of a currently shaded primitive of the image, wherein vector finding is accomplished by selecting an arbitrary vector and projecting it into the plane of the geometric normal to find the u vector, and using a cross product to find the vector v; and wherein the process further comprises modifying the normal, wherein for each primitive hit by the cast rays, a shading normal H n of the primitive is calculated at the hit point, as well as the distance to the hit point, D; if D>R, the hit is disregarded, but if D<R, a weight factor is calculated in accordance with: f=[ 1−( D/R )]·[1−( N s ·H n )] 2 ; and then, the normal H n is weighted by factor f, and the result is added to the current shading normal, N s .