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OpenGL Transformation

OpenGL Transformation. Jian-Liang Lin 2002. Transformation -1. Transformation -2. There are three matrix stacks in OpenGL architecture MODELVIEW, PROJECTION, TEXTURE glMatrixMode( GLenum mode ); mode: GL_MODELVIEW, GL_PROJECTION, GL_TEXTURE

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OpenGL Transformation

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  1. OpenGL Transformation Jian-Liang Lin 2002

  2. Transformation -1

  3. Transformation -2 • There are three matrix stacks in OpenGL architecture • MODELVIEW, PROJECTION, TEXTURE • glMatrixMode( GLenum mode ); • mode: GL_MODELVIEW, GL_PROJECTION, GL_TEXTURE • Current matrix mode is also a OpenGL state variable.

  4. Transformation -3 • Matrix Manipulation • glLoadIdentity(); • glLoadMatrix{f,d}( const TYPE* m ); • glMultMatrix{f,d}( const TYPE* m ); • glPushMatrix(); • glPopMatrix(); • Stack operation of matrix is very useful for constructing a hierarchical structures. • Ex: Render a car with four wheels.

  5. Transformation -4 • OpenGL built-in transformation: • glTranslate{f,d}( TYPE x, TYPE, y, TYPE z ); • Multiply a translation matrix into current matrix stack • glRotate{f,d}( TYPE angle, TYPE x, TYPE y, TYPE z ); • Multiply a rotation matrix about an arbitrary axis into current matrix stack • glScale{f,d}( TYPE x, TYPE y, TYPE z ); • Multiply a scaling matrix into current matrix stack

  6. Transformation -5 • Viewing transformation • Choose your viewing system • Center-orientation-up system • Apply gluLookAt Utility routine. • gluLookAt( cx, cy, cz, cx+ox, cy+oy, cz+oz, upx, upy, upz ); • ( cx, cy, cz ) is the center of the camera • ( ox, oy, oz ) is the orientation vector of the camera • ( upx, upy, upz ) is the up vector of the camera • Polar coordinate system • Combine translation and two rotation. • …

  7. Transformation -6 • Projection transformation: Perspective projection • glFrustum( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble near, GLdouble far );

  8. Transformation -7 • gluPerspective( GLdouble fovy, GLdouble aspect, GLdouble near, GLdouble far );

  9. Transformation -8 • Projection transformation: Orthogonal projection • glOrtho( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble near, GLdouble far ); • gluOrtho2D( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top ); • A helper to create a 2D projection matrix

  10. Transformation -9 • Viewport transformation • glViewport( GLint x, GLint y, GLsizei w, GLsizei h ); • Initial viewport is as the same size as the window

  11. Transformation -10 • Note: • By default, the viewpoint as well as objects in the scene are originally situated at the origin, and is looking down the negative z-axis, and has the positive y-axis as straight up.

  12. Any Question? ?

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