1)原理:将世界坐标系中的物体位置,描述为摄像机坐标系下的物体位置。
glMultMatrixf(M); glTranslated(-eyex, -eyey, -eyez);2)应用注意:OGL中还要注意,因为采用的是矩阵堆栈变换,模型变换可以默认提供glLoadIdentity ()。
Name
gluLookAt — define a viewing transformation
C Specification
void gluLookAt( | GLdouble eyeX, |
GLdouble eyeY, | |
GLdouble eyeZ, | |
GLdouble centerX, | |
GLdouble centerY, | |
GLdouble centerZ, | |
GLdouble upX, | |
GLdouble upY, | |
GLdouble upZ) ; |
Parameters
-
Specifies the position of the eye point.
-
Specifies the position of the reference point.
-
Specifies the direction of the up vector.
eyeX
,
eyeY
,
eyeZ
centerX
,
centerY
,
centerZ
upX
,
upY
,
upZ
Description
gluLookAt
creates a viewing matrix derived from an eye point, a reference point indicating the center of the scene, and an UP vector.
The matrix maps the reference point to the negative z axis and the eye point to the origin. When a typical projection matrix is used, the center of the scene therefore maps to the center of the viewport. Similarly, the direction described by the UP vector projected onto the viewing plane is mapped to the positive y axis so that it points upward in the viewport. The UP vector must not be parallel to the line of sight from the eye point to the reference point.
Let
Let UP be the vector upX upY upZ .
Then normalize as follows:
Finally, let s = f × UP ″ , and u = s s × f .
M is then constructed as follows:
and gluLookAt
is equivalent to
glMultMatrixf(M); glTranslated(-eyex, -eyey, -eyez);
Copyright
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.