fglSeparableFilter2DEXT(3G)
fglSeparableFilter2DEXT - define a separable two-dimensional convolution filter
As shipped in IRIX 6.5.19. Unchanged since IRIX 6.5.
NAME fglSeparableFilter2DEXT - define a separable two-dimensional convolution filter FORTRAN SPECIFICATION SUBROUTINE fglSeparableFilter2DEXT( INTEGER*4 target, INTEGER*4 internalformat, INTEGER*4 width, INTEGER*4 height, INTEGER*4 format, INTEGER*4 type, CHARACTER*8 row, CHARACTER*8 column ) PARAMETERS target Must be GL_SEPARABLE_2D_EXT. internalformat The internal format of the convolution filter kernel. The allowable values are GL_LUMINANCE, GL_LUMINANCE_ALPHA, GL_INTENSITY_EXT, GL_RGB, and GL_RGBA. width The number of elements in the pixel array referenced by row. (This is the width of the separable filter kernel.) height The number of elements in the pixel array referenced by column. (This is the height of the separable filter kernel.) format The format of the pixel data in row and column. The allowable values are GL_LUMINANCE, GL_LUMINANCE_ALPHA, GL_RGB, GL_RGBA, and GL_ABGR_EXT. type The type of the pixel data in row and column. The allowable values are GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, and GL_UNSIGNED_INT_10_10_10_2_EXT. row Pointer to a one-dimensional array of pixel data that is processed to build the row filter kernel. column Pointer to a one-dimensional array of pixel data that is processed to build the column filter kernel. DESCRIPTION fglSeparableFilter2DEXT builds a two-dimensional separable convolution filter kernel from two arrays of pixels. The pixel arrays specified by (width, format, type, row) and (height, format, type, column) are processed just as if they had been passed to fglDrawPixels, but processing stops after the final expansion to RGBA is completed. Next, the R, G, B, and A components of all pixels in both arrays are scaled by the four separable 2D GL_CONVOLUTION_FILTER_SCALE_EXT parameters and biased by the four separable 2D GL_CONVOLUTION_FILTER_BIAS_EXT parameters. (The scale and bias parameters are set by fglConvolutionParameterEXT using the GL_SEPARABLE_2D_EXT target and the names GL_CONVOLUTION_FILTER_SCALE_EXT and GL_CONVOLUTION_FILTER_BIAS_EXT. The parameters themselves are vectors of four values that are applied to red, green, blue, and alpha, in that order.) The R, G, B, and A values are not clamped to [0,1] at any time during this process. Each pixel is then converted to the internal format specified by internalformat. This conversion simply maps the component values of the pixel (R, G, B, and A) to the values included in the internal format (red, green, blue, alpha, luminance, and intensity). The mapping is as follows: Internal Format Red Green Blue Alpha Luminance Intensity _______________________________________________________________________ GL_LUMINANCE R GL_LUMINANCE_ALPHA A R GL_INTENSITY_EXT R GL_RGB R G B GL_RGBA R G B A The red, green, blue, alpha, luminance, and/or intensity components of the resulting pixels are stored in floating-point rather than integer format. They form two one-dimensional filter kernel images. The row image is indexed by coordinate i starting at zero and increasing from left to right. Each location in the row image is derived from element i of row. The column image is indexed by coordinate j starting at zero and increasing from bottom to top. Each location in the column image is derived from element j of column. Note that after a convolution is performed, the resulting color components are also scaled by their corresponding GL_POST_CONVOLUTION_c_SCALE_EXT parameters and biased by their corresponding GL_POST_CONVOLUTION_c_BIAS_EXT parameters (where c takes on the values RED, GREEN, BLUE, and ALPHA). These parameters are set by fglPixelTransfer. ERRORS GL_INVALID_ENUM is generated if target is not GL_SEPARABLE_2D_EXT. GL_INVALID_ENUM is generated if internalformat is not one of the allowable values. GL_INVALID_VALUE is generated if width is less than zero or greater than the maximum supported value. This value may be queried with fglGetConvolutionParameterEXT using target GL_SEPARABLE_2D_EXT and name GL_MAX_CONVOLUTION_WIDTH_EXT. GL_INVALID_VALUE is generated if height is less than zero or greater than the maximum supported value. This value may be queried with fglGetConvolutionParameterEXT using target GL_SEPARABLE_2D_EXT and name GL_MAX_CONVOLUTION_HEIGHT_EXT. GL_INVALID_ENUM is generated if format is not one of the allowable values. GL_INVALID_ENUM is generated if type is not one of the allowable values. GL_INVALID_OPERATION is generated if fglSeparableFilter2DEXT is executed between the execution of fglBegin and the corresponding execution of fglEnd. If type is set to GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT and the EXT_packed_pixels extension is not supported then a GL_INVALID_ENUM error is generated. ASSOCIATED GETS fglGetConvolutionParameterEXT, fglGetSeparableFilterEXT MACHINE DEPENDENCIES On RealityEngine, RealityEngine2, and VTX systems convolution may not be used in the following circumstances: 1. When rendering to pixmaps. 2. When fragment processing (texturing, depth buffering, alpha testing, multisampling, fog) is enabled. 3. When histogramming or minmax is enabled. 4. When either of the pixel zoom factors has a value other than 1.0 or -1.0. In these cases, fglDrawPixels and fglCopyPixels report a GL_INVALID_OPERATION error and do not transfer any pixels. SEE ALSO fglConvolutionFilter1DEXT, fglConvolutionFilter2DEXT, fglConvolutionParameterEXT, fglEnable with parameter GL_SEPARABLE_2D_EXT, fglPixelTransfer.