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Transformations II. CS5600 Computer Graphics by Rich Riesenfeld 4 March 2002. Lecture Set 6. What About Elementary Inverses?. Scale Shear Rotation Translation. Scale Inverse. Shear Inverse. Shear Inverse. Rotation Inverse. Rotation Inverse. Rotation Inverse. Translation Inverse.
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Transformations II CS5600 Computer Graphics by Rich Riesenfeld 4 March 2002 Lecture Set 6
What About Elementary Inverses? • Scale • Shear • Rotation • Translation CS5600
Scale Inverse CS5600
Shear Inverse CS5600
Shear Inverse CS5600
Rotation Inverse CS5600
Rotation Inverse CS5600
Rotation Inverse CS5600
Translation Inverse CS5600
Translation Inverse CS5600
Shear in x then in y CS5600
Shear in y then in x CS5600
Results Are Different y then x: x then y: CS5600
Want the RHR to Work CS5600
3D Positive Rotations CS5600
Transformations as a Change in Coordinate System • Useful in many situations • Use most natural coordination system locally • Tie things together in a global system CS5600
Example 4 3 2 1 CS5600
Example is the transformation that takes a point in coordinate system j and converts it to a point in coordinate system i CS5600
Example CS5600
Example CS5600
Recall the Following CS5600
Since CS5600
Change of Coordinate System • Describe the old coordinate system in terms of the new one. x’ y’ CS5600
Change of Coordinate System Move to the new coordinate system and describe the one old. Old is a negative rotation of the new. y x CS5600
What is “Perspective?” • A mechanism for portraying 3D in 2D • “True Perspective” corresponds to projection onto a plane • “True Perspective” corresponds to an ideal camera image CS5600
Many Kinds of Perspective Used • Mechanical Engineering • Cartography • Art CS5600
Perspective in Art • Naïve (wrong) • Egyptian • Cubist (unrealistic) • Esher • Miro • Matisse CS5600
Egyptian Frontalism • Head profile • Body front • Eyes full • Rigid style CS5600
Uccello's (1392-1475) handdrawing was the first extant complex geometrical form rendered accor-ding to the laws of linear perspective (Perspective Study of a Chalice, Drawing, Gabinetto dei Disegni, Uffizi, Florence, ca 1430 1440) 29
Perspective in Cubism Braque, Georges Woman with a Guitar Sorgues, autumn 1913 CS5600
Perspective in Cubism CS5600
Pablo Picaso Cabeza de mujer llorando con pañuelo 33
Perspective (Mural) Games M C Esher, Another World II (1947) CS5600
Perspective M.C. Escher, Ascending and Descending (1960) CS5600
M. C. Esher M.C. Escher, Ascending and Descending (1960) CS5600
M. C. Esher • Perspective is “local” • Perspective consistency is not “transitive” • Nonplanar (hyperbolic) projection CS5600
Nonplanar Projection M C Esher, Heaven and Hell CS5600
Nonplanar Projection M C Esher, Heaven and Hell CS5600
David McAllister The March of Progress, (1995) CS5600
Joan Miro The Tilled Field Flat Perspective:What cues are missing? CS5600
Flat Perspective:What cues are missing? Henri Matisse, La Lecon de Musique 42
Norway is at High Latitude CS5600
Isometric View CS5600
Engineering Drawing A A Section AA CS5600
Engineering Drawing: Exploded View Understanding 3D Assembly in a 2D Medium 48
“True” Perspective in 2D (x,y) h p CS5600
“True” Perspective in 2D CS5600