vpWindow(3) Library Functions Manual vpWindow(3) NAME vpWindow - multiply the projection matrix by a perspective or orthographic matrix SYNOPSIS #include <volpack.h> vpResult vpWindow(vpc, type, left, right, bottom, top, near, far) vpContext *vpc; int type; double left, right; double bottom, top; double near, far; ARGUMENTS vpc VolPack context from vpCreateContext. type Projection type code. Currently, must be VP_PARALLEL. left Coordinate of the left vertical clipping plane. right Coordinate of the right vertical clipping plane. bottom Coordinate of the bottom horizontal clipping plane. top Coordinate of the top horizontal clipping plane. near Coordinate of the near depth clipping plane. far Coordinate of the far depth clipping plane. DESCRIPTION vpWindow is used to multiply the current projection matrix by a perspective or orthographic projection matrix. The new projection matrix is defined by the coordinates of six clipping planes in the eye coordinate system (see vpCurrentMatrix(3)). The matrix maps the points (left, bottom, near) and (right, top, near) to the lower left and upper right corners of the clip- ping window. For an alternative means of specifying the projection matrix, see vpWindowPHIGS(3). Currently, only orthographic projections are supported. Perspective pro- jections will be added in a future release. The matrix for parallel projections is: A 0 0 D 0 B 0 E 0 0 C F 0 0 0 1 A = 2 / (right - left) B = 2 / (top - bottom) C = 2 / (far - near) D = (left + right) / (left - right) E = (bottom + top) / (bottom - top) F = (near + far) / (near - far) The matrix is multiplied into the projection matrix, even if the projection matrix is not the current matrix. By default, the matrix is post-multi- plied (N = N*m where N is the current matrix and m is the argument to vp- MultMatrix). The VP_CONCAT_MODE option to vpSeti can be used to select pre-multiplication. The default window is a parallel projection with left = bottom = near = -0.5, and right = top = far = 0.5. STATE VARIABLES The current matrix concatenation parameters can be retrieved with the fol- lowing state variable codes (see vpGeti(3)): VP_CONCAT_MODE. ERRORS The normal return value is VP_OK. The following error return values are possible: VPERROR_BAD_VALUE The clipping plane coordinates are invalid (left >= right, etc.). VPERROR_BAD_OPTION The type argument is invalid. SEE ALSO VolPack(3), vpCreateContext(3), vpCurrentMatrix(3), vpWindowPHIGS(3) VolPack vpWindow(3)
NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | STATE VARIABLES | ERRORS | SEE ALSO
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