fglMap1(3G)
fglMap1d, fglMap1f - define a one-dimensional evaluator
As shipped in IRIX 6.5.22. Last changed in IRIX 6.5.15.
NAME fglMap1d, fglMap1f - define a one-dimensional evaluator FORTRAN SPECIFICATION SUBROUTINE fglMap1d( INTEGER*4 target, REAL*4 u1, REAL*4 u2, INTEGER*4 stride, INTEGER*4 order, CHARACTER*8 points ) SUBROUTINE fglMap1f( INTEGER*4 target, REAL*4 u1, REAL*4 u2, INTEGER*4 stride, INTEGER*4 order, CHARACTER*8 points ) PARAMETERS target Specifies the kind of values that are generated by the evaluator. Symbolic constants GL_MAP1_VERTEX_3, GL_MAP1_VERTEX_4, GL_MAP1_INDEX, GL_MAP1_COLOR_4, GL_MAP1_NORMAL, GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2, GL_MAP1_TEXTURE_COORD_3, and GL_MAP1_TEXTURE_COORD_4 are accepted. u1, u2 Specify a linear mapping of u, as presented to fglEvalCoord1, to ^, the variable that is evaluated by the equations specified by this command. stride Specifies the number of floats or doubles between the beginning of one control point and the beginning of the next one in the data structure referenced in points. This allows control points to be embedded in arbitrary data structures. The only constraint is that the values for a particular control point must occupy contiguous memory locations. order Specifies the number of control points. Must be positive. points Specifies a pointer to the array of control points. DESCRIPTION Evaluators provide a way to use polynomial or rational polynomial mapping to produce vertices, normals, texture coordinates, and colors. The values produced by an evaluator are sent to further stages of GL processing just as if they had been presented using fglVertex, fglNormal, fglTexCoord, and fglColor commands, except that the generated values do not update the current normal, texture coordinates, or color. All polynomial or rational polynomial splines of any degree (up to the maximum degree supported by the GL implementation) can be described using evaluators. These include almost all splines used in computer graphics: B-splines, Bezier curves, Hermite splines, and so on. Evaluators define curves based on Bernstein polynomials. Define p(^) as n R n p(^) = B (^)R i=0 i i n where R is a control point and B (^) is the ith Bernstein polynomial of i i degree n (order = n + 1): ( ) n n i n-i B (^) = | |^ (1-^) i (i ) Recall that ( ) 0 n 0 = 1 and | | = 1 ( 0 ) fglMap1 is used to define the basis and to specify what kind of values are produced. Once defined, a map can be enabled and disabled by calling fglEnable and fglDisable with the map name, one of the nine predefined values for target described below. fglEvalCoord1 evaluates the one- dimensional maps that are enabled. When fglEvalCoord1 presents a value u, the Bernstein functions are evaluated using ^, where _______ ^ = u2 - u1 target is a symbolic constant that indicates what kind of control points are provided in points, and what output is generated when the map is evaluated. It can assume one of nine predefined values: GL_MAP1_VERTEX_3 Each control point is three floating-point values representing x, y, and z. Internal fglVertex3 commands are generated when the map is evaluated. GL_MAP1_VERTEX_4 Each control point is four floating-point values representing x, y, z, and w. Internal fglVertex4 commands are generated when the map is evaluated. GL_MAP1_INDEX Each control point is a single floating-point value representing a color index. Internal fglIndex commands are generated when the map is evaluated but the current index is not updated with the value of these fglIndex commands. GL_MAP1_COLOR_4 Each control point is four floating-point values representing red, green, blue, and alpha. Internal fglColor4 commands are generated when the map is evaluated but the current color is not updated with the value of these fglColor4 commands. GL_MAP1_NORMAL Each control point is three floating-point values representing the x, y, and z components of a normal vector. Internal fglNormal commands are generated when the map is evaluated but the current normal is not updated with the value of these fglNormal commands. GL_MAP1_TEXTURE_COORD_1 Each control point is a single floating-point value representing the s texture coordinate. Internal fglTexCoord1 commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these fglTexCoord commands. GL_MAP1_TEXTURE_COORD_2 Each control point is two floating-point values representing the s and t texture coordinates. Internal fglTexCoord2 commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these fglTexCoord commands. GL_MAP1_TEXTURE_COORD_3 Each control point is three floating-point values representing the s, t, and r texture coordinates. Internal fglTexCoord3 commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these fglTexCoord commands. GL_MAP1_TEXTURE_COORD_4 Each control point is four floating-point values representing the s, t, r, and q texture coordinates. Internal fglTexCoord4 commands are generated when the map is evaluated but the current texture coordinates are not updated with the value of these fglTexCoord commands. stride, order, and points define the array addressing for accessing the control points. points is the location of the first control point, which occupies one, two, three, or four contiguous memory locations, depending on which map is being defined. order is the number of control points in the array. stride specifies how many float or double locations to advance the internal memory pointer to reach the next control point. NOTES As is the case with all GL commands that accept pointers to data, it is as if the contents of points were copied by fglMap1 before fglMap1 returns. Changes to the contents of points have no effect after fglMap1 is called. ERRORS GL_INVALID_ENUM is generated if target is not an accepted value. GL_INVALID_VALUE is generated if u1 is equal to u2. GL_INVALID_VALUE is generated if stride is less than the number of values in a control point. GL_INVALID_VALUE is generated if order is less than 1 or greater than the return value of GL_MAX_EVAL_ORDER. GL_INVALID_OPERATION is generated if fglMap1 is executed between the execution of fglBegin and the corresponding execution of fglEnd. ASSOCIATED GETS fglGetMap fglGet with argument GL_MAX_EVAL_ORDER fglIsEnabled with argument GL_MAP1_VERTEX_3 fglIsEnabled with argument GL_MAP1_VERTEX_4 fglIsEnabled with argument GL_MAP1_INDEX fglIsEnabled with argument GL_MAP1_COLOR_4 fglIsEnabled with argument GL_MAP1_NORMAL fglIsEnabled with argument GL_MAP1_TEXTURE_COORD_1 fglIsEnabled with argument GL_MAP1_TEXTURE_COORD_2 fglIsEnabled with argument GL_MAP1_TEXTURE_COORD_3 fglIsEnabled with argument GL_MAP1_TEXTURE_COORD_4 SEE ALSO fglBegin, fglColor, fglEnable, fglEvalCoord, fglEvalMesh, fglEvalPoint, fglMap2, fglMapGrid, fglNormal, fglTexCoord, fglVertex