1. A computer-implemented method for rendering a three-dimensional computer-aided design model, the method comprising: from a plurality of data fragments for a certain pixel location of a three-dimensional computer aided design (CAD) model, storing in a computer memory an unordered subset of the plurality of data fragments for the certain pixel location of the three-dimensional computer aided design (CAD) model, the subset being for the data fragments closest to a viewer; once the subset is stored, receiving a next data fragment having a depth value representative of position of the next data fragment, and determining from the depth value whether the next data fragment is closer to the viewer than at least one of the data fragments in the stored unordered subset; if the depth value positions the next data fragment closer to the viewer than at least one of the data fragments in the stored unordered subset, replacing in the computer memory the one data fragment in the subset having a farthest position according to depth value with the next data fragment, wherein the farthest position according to depth value indicates a position farthest from the viewer, and wherein said replacing resulting in the stored unordered subset having a number of data fragments closest to the viewer; sorting the data fragments of the resulting stored unordered subset according to a respective depth value of each of the data fragments in the subset; and performing a blending process that uses the sorted data fragments of the subset to compute a pixel value representing a transparency characteristic of the three-dimensional CAD model at the certain pixel location.