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Viewing and Navigating using OpenGL

Viewing and Navigating using OpenGL. The LookAt Function. The GLU library contains the function gluLookAt to form the required modelview matrix through a simple interface Note the need for setting an up direction Still need to initialize Can concatenate with modeling transformations

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Viewing and Navigating using OpenGL

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  1. Viewing and Navigatingusing OpenGL

  2. The LookAt Function • The GLU library contains the function gluLookAt to form the required modelview matrix through a simple interface • Note the need for setting an up direction • Still need to initialize • Can concatenate with modeling transformations • Example: isometric view of cube aligned with axes glMatrixMode(GL_MODELVIEW): glLoadIdentity(); gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0., 1.0. 0.0);

  3. gluLookAt glLookAt(eyex, eyey, eyez, atx, aty, atz, upx, upy, upz)

  4. Outside-In Viewing Object is centered. Observer navigates on a sphere surrounding the object.

  5. Inside-Out Viewing Viewer centered. Observer navigates, looks toward a point On the sphere. Sphere center moves with observer.

  6. Inside-Out Viewing Viewer centered. Observer navigates, looks toward a point On the sphere. Sphere center moves with observer.

  7. y x z Some Spherical Geometry (x,y,z) r q f

  8. y x z Viewing: Outside-In (x,y,z) gluLookAt(x,y,z,0,0,0,0,1,0);

  9. 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)

  10. 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

  11. y x z Viewing: Inside Out, from Origin (x,y,z) gluLookAt(0,0,0,x,y,z,0,1,0);

  12. Y’ X’ z’ Viewing: Inside Out, from Arbitrary Point (x,y,z) gluLookAt(x0,y0,z0,x,y,z,0,1,0);

  13. 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,xo+x,yo+y,zo+z,0,1,0); //multiply viewing transformation glutSolidTeapot(1.0);

  14. 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

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