A perspective texture mapping circuit (10) is disclosed. In a perspective texture mapping mode, an inverse z gradient and corresponding inverse z polygon vertex value is loaded into a first interpolator circuit (14), and texture address product gradients with corresponding polygon vertex texture address product values are loaded into a second and third interpolator circuit (16 and 18). The first interpolator circuit (14) interpolates a sequence of inverse z values for the surface of the polygon. The second and third interpolator circuits (16 and 18) interpolate corresponding texture address product values for each interpolated inverse z value. The texture address product values are divided by the corresponding inverse z value in a divider circuit (12) to generate texture address values. Texture address values are coupled to texture memory (20) to generate texel values which are passed onto an output FIFO (26). In a color interpolation mode, each pixel includes three color component. Different color component gradients and vertex color component values are coupled to each interpolator circuit (14, 16 and 18) which interpolate corresponding color component values for the surface of the polygon. Corresponding color component values are coupled together to the output FIFO (26) to generate color pixels.
A method of the present invention relates to a method of blending a plurality of pixels on a texture map and to a plural pixel blending circuit and image processing device using this is disclosed. The method of blending a plurality of pixels on a texture map corresponding to the pixels constituting a polygon, thereby finding texture data to be pasted on to the pixels constituting the polygon, includes the steps of: determining whether or not there are transparent pixels in said plurality of pixels on the texture map; if there are no transparent pixels, blending said plurality of pixels on the texture map in accordance with the ratio with which a pixel constituting the polygon corresponds therewith; if some of the plurality of pixels on the texture map are transparent pixels, substituting the transparent pixels by other adjacent pixels which are not transparent; and if all of the plurality of pixels on the texture map are transparent pixels, ignoring the plurality of pixels on the texture map.
A spatial filter having coefficients selected and distributed within an array, so that when the array is divided non-diagonally into four equal quadrants, (1) the coefficients are of constant sign within each quadrant; (2) coefficients in diagonally opposed quadrants have like sign; and (3) coefficients in non-diagonally neighboring quadrants have unlike sign. In a preferred embodiment, coefficients cause the array to form a "saddle" shape when the coefficient values are representative of the local slope on a surface described by the array. This "saddle" shape enables improved filtration properties. The inventive spatial filter is further advantageously embodied in architecture comprising an array of individual calculation modules corresponding to the filter array. Rows of modules are coupled together in parallel. The input signal is fed to each row concurrently via FIFO buffers, enabling concurrent calculation operations. After calculation, output values for each module are accumulated and summed, the result being placed into an output stream. The FIFO buffers then present the next input values in the input stream to the calculation modules, and so on. The result is a low-latency "streaming" filtration that is further economical on hardware, requiring only FIFO storage resources. Advantageously, the entire inventive filter may be conveniently deployed as a digital signal processor ("DSP") on a unitary integrated circuit chip.
A graphics accelerator pipeline including a rasterizer stage, a texture stage, and a combiner stage capable of producing realistic output images by mapping irregular textures to surfaces.
Method and apparatus for rendering texture to an object to be displayed on a pixel screen display. This technique makes use of linear interpolation between perspectively correct texture address to calculate rates of change of individual texture addresses components to determine a selection of the correct LOD map to use and intermediate texture addresses for pixels of the object between the perspectively correct addresses. The method first determines perspectively correct texture address values associated with four corners of a predefined span or grid of pixels. Then, a linear interpolation technique is implemented to calculate a rate of change of texture address components in the screen x and y directions for pixels between the perspectively bound span corners. This linear interpolation technique is performed in both screen directions to thereby create a potentially unique level of detail value for each pixel, which is then used as an index to select the correct pre-filtered LOD texture map. When mapping an individually determined LOD value per pixel, the effect of producing undesirable artifacts that may appear if a single LOD for an entire span or polygon is used, is obviated.
Method and apparatus for rendering texture to an object to be displayed on a pixel screen display. This technique makes use of linear interpolation between perspectively correct texture address to calculate rates of change of individual texture addresses components to determine a selection of the correct LOD map to use and intermediate texture addresses for pixels of the object between the perspectively correct addresses. The method first determines perspectively correct texture address values associated with four corners of a predefined span or grid of pixels. Then, a linear interpolation technique is implemented to calculate a rate of change of texture address components in the screen x and y directions for pixels between the perspectively bound span corners. This linear interpolation technique is performed in both screen directions to thereby create a potentially unique level of detail value for each pixel, which is then used as an index to select the correct pre-filtered LOD texture map. When mapping an individually determined LOD value per pixel, the effect of producing undesirable artifacts that may appear if a single LOD for an entire span or polygon is used, is obviated.
