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<HTML><BODY><PRE> <STRONG>NAME</STRONG> <STRONG>fglClipPlane</STRONG> - specify a plane against which all geometry is clipped <STRONG>FORTRAN</STRONG> <STRONG>SPECIFICATION</STRONG> SUBROUTINE <STRONG>fglClipPlane</STRONG>( INTEGER*4 <EM>plane</EM>, CHARACTER*8 <EM>equation</EM> ) <STRONG>PARAMETERS</STRONG> <EM>plane</EM> Specifies which clipping plane is being positioned. Symbolic names of the form <STRONG>GL_CLIP_PLANE</STRONG><EM>i</EM>, where <EM>i</EM> is an integer between 0 and <STRONG>GL_MAX_CLIP_PLANES</STRONG> -1, are accepted. <EM>equation</EM> Specifies the address of an array of four double- precision floating-point values. These values are interpreted as a plane equation. <STRONG>DESCRIPTION</STRONG> Geometry is always clipped against the boundaries of a six- plane frustum in <EM>x</EM>, <EM>y</EM>, and <EM>z</EM>. <STRONG>fglClipPlane</STRONG> allows the specification of additional planes, not necessarily perpendicular to the <EM>x</EM>, <EM>y</EM>, or <EM>z</EM> axis, against which all geometry is clipped. To determine the maximum number of additional clipping planes, call <STRONG>fglGetIntegerv</STRONG> with argument <STRONG>GL_MAX_CLIP_PLANES</STRONG>. All implementations support at least six such clipping planes. Because the resulting clipping region is the intersection of the defined half- spaces, it is always convex. <STRONG>fglClipPlane</STRONG> specifies a half-space using a four-component plane equation. When <STRONG>fglClipPlane</STRONG> is called, <EM>equation</EM> is transformed by the inverse of the modelview matrix and stored in the resulting eye coordinates. Subsequent changes to the modelview matrix have no effect on the stored plane- equation components. If the dot product of the eye coordinates of a vertex with the stored plane equation components is positive or zero, the vertex is <EM>in</EM> with respect to that clipping plane. Otherwise, it is <EM>out</EM>. To enable and disable clipping planes, call <STRONG>fglEnable</STRONG> and <STRONG>fglDisable</STRONG> with the argument <STRONG>GL_CLIP_PLANE</STRONG><EM>i</EM>, where <EM>i</EM> is the plane number. All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates and are disabled. <STRONG>NOTES</STRONG> It is always the case that <STRONG>GL_CLIP_PLANE</STRONG>i = <STRONG>GL_CLIP_PLANE0</STRONG> + i. <STRONG>ERRORS</STRONG> <STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>plane</EM> is not an accepted value. <STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>fglClipPlane</STRONG> is executed between the execution of <STRONG>fglBegin</STRONG> and the corresponding execution of <STRONG>fglEnd</STRONG>. <STRONG>ASSOCIATED</STRONG> <STRONG>GETS</STRONG> <STRONG>fglGetClipPlane</STRONG> <STRONG>fglIsEnabled</STRONG> with argument <STRONG>GL_CLIP_PLANE</STRONG><EM>i</EM> <STRONG>SEE</STRONG> <STRONG>ALSO</STRONG> <STRONG>fglEnable</STRONG></PRE></BODY></HTML>⌨️ 快捷键说明
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