Method, system, and computer program product for bump mapping in tangent space

A system for shading a computer graphics image, the computer graphics image including an object surface, the system comprising:

• a tangent space transform module;
• a bump mapping module;
• and
• a lighting module;
• wherein said tangent space transform module builds a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface and transforms a shading vector at said point into a tangent space defined by said tangent space transform matrix to form a corresponding tangent space shading vector, said tangent space shading vector being output to said bump mapping module, and
• said bump mapping module performs a vector operation between said tangent space shading vector and a perturbed normal in tangent space at said point, and provides an output representative of said vector operation, and
• said lighting module computes a shading value for said point based on said vector operation output;
• whereby, said shading value can be mapped to a pixel to shade the object surface.

A system for shading an object surface, the system comprising:

• means for building a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• means for transforming a shading vector at said point into a tangent space defined by said tangent space transform matrix to form a corresponding tangent space shading vector;
• means for performing a vector operation between said tangent space shading vector and a perturbed normal in tangent space at said point;
• and
• means for computing a shading value for said point based on said vector operation;
• whereby, said shading value can be mapped to a pixel to shade the object surface when rendered on a computer graphics display.

A computer program product comprising a computer useable medium having computer program logic recorded thereon for enabling a graphics processor in a computer system to shade an object surface in a computer graphic image, said computer program logic comprising:

• means for enabling the graphics processor to build a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• means for enabling the graphics processor to transform a shading vector at said point into a tangent space defined by said tangent space transform matrix to form a corresponding tangent space shading vector;
• means for enabling the graphics processor to perform a vector operation between said tangent space shading vector and a perturbed normal in tangent space at said point;
• and
• means for enabling the graphics processor to compute a shading value for said point based on said vector operation;
• whereby, said shading value can be mapped to a pixel to shade the object surface rendered on a computer graphics display.

A method for shading a computer graphics image, the computer graphics image including an object surface, comprising the steps of:

• building a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• determining tangent space lighting and viewing vectors at said point in a tangent space defined by said tangent space transform matrix;
• generating a combination of images including an Lz.sub.TS image, a height field image, a z component diffuse image, and a shifted image sL, wherein said Lz.sub.TS image represents an unperturbed normal dotted with said tangent space lighting vector L.sub.TS, said height image represents a height field f(u,v) for bump mapping, said z component diffuse image represents a sum of said Lz image and said height image, and said shifted image approximates a partial sum sL equal to -(.differential.f/.differential.u)*Lx.sub.TS +-(.differential.f/.differential.v)*Ly.sub.TS ;
• generating a diffuse image based on the difference between said shifted image and said z component diffuse image;
• and
• forming a lit image based on at least said diffuse image;
• whereby, said lit image can be mapped as texture to the object surface when shading the computer graphics image.

A method for shading a computer graphics image, the computer graphics image including an object surface, comprising the steps of:

• building a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• determining a tangent space half angle vector H.sub.TS at said point in a tangent space defined by said tangent space transform matrix;
• generating a combination of images including an Hz.sub.TS image, a height field image, a z component specular image, and a shifted image sH, wherein said Hz.sub.TS image represents an unperturbed normal dotted with said tangent space half angle vector H.sub.TS, said height image represents a height field f(u,v) for bump mapping, said z component specular image represents a sum of said Hz.sub.TS image and said height image, and said shifted image approximates a partial sum sH equal to -(.differential.f/.differential.u)*Hx.sub.TS +-(.differential.f/.differential.v)*Hy.sub.TS ;
• and
• generating a specular image based on the difference between said shifted image and said z component specular image;
• and
• forming a lit image based on at least said specular image;
• whereby, said lit image can be mapped as texture to the object surface when shading the computer graphics image.

A system for shading a computer graphics image, the computer graphics image including an object surface, comprising:

• means for building a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• means for determining tangent space lighting and viewing vectors at said point in a tangent space defined by said tangent space transform matrix;
• means for generating a combination of images including an Lz.sub.TS image, a height field image, a z component diffuse image, and a shifted image sL, wherein said Lz.sub.TS image represents an unperturbed normal dotted with said tangent space lighting vector L.sub.TS, said height image represents a height field f(u,v) for bump mapping, said z component diffuse image represents a sum of said Lz image and said height image, and said shifted image approximates a partial sum sL equal to -(.differential.f/.differential.u)*Lx.sub.TS +-(.differential.f/.differential.v)*Ly.sub.TS ;
• means for generating a diffuse image based on the difference between said shifted image and said z component diffuse image;
• and
• means for forming a lit image based on at least said diffuse image;
• whereby, said lit image can be mapped as texture to the object surface when shading the computer graphics image.

A system for shading a computer graphics image, the computer graphics image including an object surface, comprising:

• means for building a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• means for determining a tangent space half angle vector H.sub.TS at said point in a tangent space defined by said tangent space transform matrix;
• means for generating a combination of images including an Hz.sub.TS image, a height field image, a z component specular image, and a shifted image sH, wherein said Hz.sub.TS image represents an unperturbed normal dotted with said tangent space half angle vector H.sub.TS, said height image represents a height field f(u,v) for bump mapping, said z component specular image represents the sum of said Hz.sub.TS image and said height image, and said shifted image approximates a partial sum sH equal to -(.differential.f/.differential.u)*Hx.sub.TS +-(.differential.f/.differential.v)*Hy.sub.TS ;
• means for generating a specular image based on the difference between said shifted image and said z component specular image;
• and
• means for forming a lit image based on at least said specular image;
• whereby, said lit image can be mapped as texture to the object surface when shading the computer graphics image.

A method for shading a computer graphics image, the computer graphics image including an object surface, comprising the steps of:

• building a tangent space transform matrix, said tangent space transform matrix having elements comprised of normal, tangent, and binormal vector components determined at a point on the object surface;
• determining tangent space lighting and viewing vectors at said point in a tangent space defined by said tangent space transform matrix;
• generating and mapping to the object surface a combination of images including an Lz.sub.TS image, a height field image, a z component diffuse image, and a shifted image sL, wherein said Lz.sub.TS image represents an unperturbed normal dotted with said tangent space lighting vector L.sub.TS, said height image represents a height field f(u,v) for bump mapping, said z component diffuse image represents a sum of said Lz image and said height image, and said shifted image approximates a partial sum sL equal to -(.differential.f/.differential.u)*Lx.sub.TS +-(.differential.f/.differential.v)*Ly.sub.TS ;
• generating a diffuse image based on the difference between said shifted image and said z component diffuse image;
• and
• forming a lit image based on at least said diffuse image.

A system for shading a computer graphics image, comprising:

• Phong shading hardware;
• a texture memory for storing a tangent space perturbed normal texture map;
• and
• a switch coupled between said Phong shading hardware and said texture memory;
• whereby, tangent space bump mapping shades the computer graphics image when said switch is in a state connecting said texture memory to said Phone shading hardware.