A method of extracting surfaces in three-dimensional data includes receiving as inputs three-dimensional data and a seed point p located on a surface to be extracted. The method further includes propagating a front outwardly from the seed point p and extracting a plurality of ridge curves based on the propagated front. A surface boundary is detected based on a comparison of distances between adjacent ridge curves and the desired surface is extracted based on the detected surface boundary.

Methods and systems of generating an image gradient are presented. In one example, image data for generating a two-dimensional digital image is provided to a hardware graphics processor. The image data may include a single pixel along a first direction of the digital image and multiple pixels along a second direction of the digital image. The pixels along the second direction of the digital image may include an image gradient. A one-dimensional stretching operation of the hardware graphics processor is initiated based on the image data to generate the digital image. In response to the stretching operation, the digital image may include multiple pixels along the first direction for each of the single pixels, wherein each of the multiple pixels along the first direction for a corresponding pixel of the single pixels comprises the corresponding pixel.

Selection of an area of an image can be received. Selection of a subset of a plurality of predefined patterns may be received. A plurality of patterns can be generated. At least one generated pattern in the plurality of patterns may be based at least in part on one or more predefined patterns in the subset. Selection of another subset of patterns may be received. At least one pattern in the other subset of patterns may be selected from the plurality of predefined patterns and/or the generated patterns. Another plurality of patterns can be generated. At least one generated pattern in this plurality of patterns may be based at least on part on one or more patterns in the other subset. Selection of a generated pattern from the generated other plurality of patterns may be received. The selected area of the image may be populated with the selected generated pattern.