Method, computer program product and system for rendering soft shadows in a frame representing a 3D-scene

The method according to the preceding claim, wherein the step of applying said cubemap while performing a stencil test operation comprises:

• performing a per-pixel test against values stored in the stencil buffer and preventing rendering a fragment of said scene at the pixel of interest if the value stored in the stencil buffer at the pixel of interest is different from the nil value;
• accessing said cubemap via vectors given by 3D texture coordinates, where the greatest magnitude component is used to select a face of said cubemap and the other two components are used to select a texel from said face;
• and
• performing a texture coordinate generation for specifying a texture coordinate and selecting a pixel of an appropriate cubemap face.

A computer program product for rendering soft shadows in a frame representing a three-dimensional scene, which is defined by a list of polygons and comprises a plurality of three-dimensional objects, comprising:

• program code means for performing, from a light source's point of view, the steps of:
• determining edges casting shadows from said list of polygons;
• computing shadow volumes and computing soft shadow edges from said edges casting shadows;
• creating up to six squared empty textures of the same size, each of them becoming a face of a cubemap representing a cube centered at the light source's point of view, said faces of said cubemap being aligned with orthogonal major axes with the light source's position as origin;
• rendering into at least one face of said cubemap an appropriate part of said scene with full brightness color and rendering a representation of soft shadows into said at least one face of said cubemap using said edges casting shadows and said soft shadow edges computed;
• program code means for performing, from a point of view of a viewer viewing said scene, the steps of:
• rendering a visible part of the scene into a z-buffer with colors, lighting and texture information disabled for generating depth information;
• rendering said shadow volumes into a stencil buffer in combination with said z-buffer information;
• and
• in a single pass, rendering said scene with colors, lighting and texture information enabled and applying said cubemap to said scene for rendering said representation of said soft shadows into said scene using a texture coordinate generation while performing a stencil test operation for preventing the scene to be drawn in shadowed areas, to produce a soft shadowed image.

The computer program product according to the preceding claim, wherein a program code means for applying said cubemap while performing a stencil test operation comprises:

• program code means for performing a per-pixel test against values stored in the stencil buffer and preventing rendering a fragment of said scene at the pixel of interest if the value stored in the stencil buffer at the pixel of interest is different from the nil value;
• program code means for accessing said cubemap via vectors given by 3D texture coordinates, where the greatest magnitude component is used to select a face of said cubemap and the other two components are used to select a texel from said face;
• and
• program code means for performing a texture coordinate generation for specifying a texture coordinate and selecting a pixel of an appropriate cubemap face.

A system for rendering a three-dimensional scene comprising a plurality of three-dimensional objects formed by polygons and for rendering soft shadows in said scene:

• a) a color buffer for storing color values;
• b) a z-buffer for storing depth values;
• c) a stencil buffer for storing stencil mask information;
• d) texture memory for storing texture information;
• e) a rasterizer for converting each of the polygons into color, depth and stencil values;
• f) a first pixel engine in communication with the rasterizer and the texture memory for copying or drawing directly a portion of the color buffer into an appropriate texture representing a specific cubemap side;
• g) a second pixel engine in communication with the rasterizer, the z-buffer and the stencil buffer for receiving said polygons and performing a depth compare operation and a stencil test operation based on the result of the depth compare operation;
• and
• h) a third pixel engine in communication with the rasterizer, the z-buffer, the stencil buffer and the texture memory for receiving said polygons and performing a depth compare operation, a stencil test operation and a texture coordinate generation operation, based on the result from the depth compare and stencil test, for transferring into the non-shadowed areas of the frame buffer the appropriate pixels of the appropriate side of the cubemap.