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author | Reinhard Tartler <siretart@tauware.de> | 2011-10-10 17:43:39 +0200 |
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committer | Reinhard Tartler <siretart@tauware.de> | 2011-10-10 17:43:39 +0200 |
commit | f4092abdf94af6a99aff944d6264bc1284e8bdd4 (patch) | |
tree | 2ac1c9cc16ceb93edb2c4382c088dac5aeafdf0f /nx-X11/extras/ogl-sample/main/doc/man/manglu/standard/perspective.gl | |
parent | a840692edc9c6d19cd7c057f68e39c7d95eb767d (diff) | |
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Imported nx-X11-3.1.0-1.tar.gznx-X11/3.1.0-1
Summary: Imported nx-X11-3.1.0-1.tar.gz
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Imported nx-X11-3.1.0-1.tar.gz
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Diffstat (limited to 'nx-X11/extras/ogl-sample/main/doc/man/manglu/standard/perspective.gl')
-rw-r--r-- | nx-X11/extras/ogl-sample/main/doc/man/manglu/standard/perspective.gl | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/nx-X11/extras/ogl-sample/main/doc/man/manglu/standard/perspective.gl b/nx-X11/extras/ogl-sample/main/doc/man/manglu/standard/perspective.gl new file mode 100644 index 000000000..c33fdbd91 --- /dev/null +++ b/nx-X11/extras/ogl-sample/main/doc/man/manglu/standard/perspective.gl @@ -0,0 +1,106 @@ +_C_ License Applicability. Except to the extent portions of this file are +_C_ made subject to an alternative license as permitted in the SGI Free +_C_ Software License B, Version 1.1 (the "License"), the contents of this +_C_ file are subject only to the provisions of the License. You may not use +_C_ this file except in compliance with the License. You may obtain a copy +_C_ of the License at Silicon Graphics, Inc., attn: Legal Services, 1600 +_C_ Amphitheatre Parkway, Mountain View, CA 94043-1351, or at: +_C_ +_C_ http://oss.sgi.com/projects/FreeB +_C_ +_C_ Note that, as provided in the License, the Software is distributed on an +_C_ "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS +_C_ DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND +_C_ CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A +_C_ PARTICULAR PURPOSE, AND NON-INFRINGEMENT. +_C_ +_C_ Original Code. The Original Code is: OpenGL Sample Implementation, +_C_ Version 1.2.1, released January 26, 2000, developed by Silicon Graphics, +_C_ Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc. +_C_ Copyright in any portions created by third parties is as indicated +_C_ elsewhere herein. All Rights Reserved. +_C_ +_C_ Additional Notice Provisions: The application programming interfaces +_C_ established by SGI in conjunction with the Original Code are The +_C_ OpenGL(R) Graphics System: A Specification (Version 1.2.1), released +_C_ April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version +_C_ 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X +_C_ Window System(R) (Version 1.3), released October 19, 1998. This software +_C_ was created using the OpenGL(R) version 1.2.1 Sample Implementation +_C_ published by SGI, but has not been independently verified as being +_C_ compliant with the OpenGL(R) version 1.2.1 Specification. +_C_ +_C_ $Date: 2004/03/14 08:29:09 $ $Revision: 1.1.1.4 $ +_C_ The first character in this file must be an '_'! +_C_ Anything on a line after _C_ is ignored +_define(_filters,eqn)_C_ +_C_ eqn is automatically replaced with neqn for nroff +_header(Perspective, set up a perspective projection matrix) +_names(Perspective) +.EQ +delim $$ +.EN +.SH PARAMETERS +_phead(_param1) +Specifies the field of view angle, in degrees, in the \f2y\fP direction. +_phead(_param2) +Specifies the aspect ratio that determines +the field of view in the \f2x\fP direction. +The aspect ratio is the ratio of \f2x\fP (width) to \f2y\fP (height). +_phead(_param3) +Specifies the distance from the viewer to the near clipping plane +(always positive). +_phead(_param4) +Specifies the distance from the viewer to the far clipping plane +(always positive). +.SH DESCRIPTION +_cmnd specifies a viewing frustum into the world coordinate system. +In general, the aspect ratio in _cmnd should match the aspect ratio +of the associated viewport. For example, $ _eqnparam2 ~=~ 2.0 $ means +the viewer's +angle of view is twice as wide in \f2x\fP as it is in \f2y\fP. +If the viewport is +twice as wide as it is tall, it displays the image without distortion. +.P +The matrix generated by _cmnd is multipled by the current matrix, +just as if _glcmnd(MultMatrix) were called with the generated matrix. +To load the perspective matrix onto the current matrix stack instead, +precede the call to _cmnd with a call to _glcmnd(LoadIdentity). +.P +Given \f2f\fP defined as follows: +.sp +.ce +.EQ +f ~=~ cotangent"("{_eqnparam1 over 2}")" +.EN +.bp +The generated matrix is +.sp +.ce +.EQ +left ( ~~ down 130 { matrix { + ccol { {f over _eqnparam2} above 0 above 0 above 0 } + ccol { 0 above f above 0 above 0 } + ccol { 0 above 0 above {{_eqnparam4 + _eqnparam3} over {_eqnparam3 - _eqnparam4}} above -1 } + ccol { 0 above 0 above {{2 * _eqnparam4 * _eqnparam3} over {_eqnparam3 - _eqnparam4}} above 0} +}} ~~~ right ) +.EN + +.SH NOTES +Depth buffer precision is affected by the values specified for +_param3 and _param4. +The greater the ratio of _param4 to _param3 is, +the less effective the depth buffer will be at distinguishing between +surfaces that are near each other. +If +.sp +.ce +$r ~=~ _eqnparam4 over _eqnparam3$ +.sp +.P +roughly $log sub 2 r$ bits of depth buffer precision are lost. +Because $r$ approaches infinity as _param3 approaches 0, +_param3 must never be set to 0. +.SH SEE ALSO +_glcmnd(Frustum), _glcmnd(LoadIdentity), +_glcmnd(MultMatrix), _cmnd(Ortho2D) |