Viewing and Navigating using OpenGL

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Viewing and Navigatingusing OpenGL
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Outside-In Viewing
Object is centered. Observer navigates on a
sphere surrounding the object.
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Inside-Out Viewing
Viewer centered. Observer navigates, looks
toward a point On the sphere. Sphere center
moves with observer.
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Inside-Out Viewing
Viewer centered. Observer navigates, looks
toward a point On the sphere. Sphere center
moves with observer.
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Some Spherical Geometry
(x,y,z)
r
q
f
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Viewing Outside-In
(x,y,z)
gluLookAt(x,y,z,0,0,0,0,1,0)
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Outside In ViewingSample Code
glLoadIdentity() // start with an identity in
the MODELVIEW transformation x radius
cos(theta) cos(phi) y radius sin(theta) z
-radius cos(theta) sin(phi) gluLookAt(x,y,z
,0,0,0,0,1,0) //multiply viewing component of
transformation glutSolidTeapot(1.0) // draw
what is being looked at (around origin)
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Viewing Outside In Possible Navigation Key
Mapping

• GLUT_KEY_LEFT increase phi
• GLUT_KEY_RIGHT decrease phi
• GLUT_KEY_UP increase theta
• GLUT_KEY_DOWN decrease theta
• GLUT_KEY_PAGE_UP increase radius
• GLUT_KEY_PAGE_DOWN decrease radius

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Viewing Inside Out, from Origin
(x,y,z)
gluLookAt(0,0,0,x,y,z,0,1,0)
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Viewing Inside Out, from Arbitrary Point
(x,y,z)
gluLookAt(x0,y0,z0,x,y,z,0,1,0)
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Inside Out ViewingSample Code
glLoadIdentity() // start with an identity in
the MODELVIEW transformation x radius
cos(theta) cos(phi) y radius sin(theta) z
-radius cos(theta) sin(phi) gluLookAt(xo,yo
,zo,xox,yoy,zoz,0,1,0) //multiply viewing
transformation glutSolidTeapot(1.0)
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Viewing Inside Out Possible Navigation Key
Mapping

• GLUT_KEY_LEFT increase phi (look left)
• GLUT_KEY_RIGHT decrease phi (look right)
• GLUT_KEY_UP increase theta (look up)
• GLUT_KEY_DOWN decrease theta (look down)
• GLUT_KEY_PAGE_UP walk in direction of view
• GLUT_KEY_PAGE_DOWN walk away from direction of
  view