COMPUTER SCIENCE AND ENGINEERING
COMPUTER GRAPHICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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What should be done to rotate around a point that is not the origin?
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Translate to origin, rotate about origin, then translate back to original position
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Rotations can only be performed around the origin.
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Perform a glRotate and specify the point to rotate around
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None of the above
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Explanation:
Detailed explanation-1: -If your centre of rotation is not the origin, all you have to do is give each point “fake” coordinates – the ones they would have if your centre of rotation were the origin.
Detailed explanation-2: -Positive rotations are counterclockwise. Negative rotations are clockwise. For example, to rotate the point (2, 5) counterclockwise about the origin by 90 degrees, we use the rule: (x, y)→(−y, x) ( x, y ) → ( − y, x ) .
Detailed explanation-3: -Rotation by 180° about the origin: The rule for a rotation by 180° about the origin is (x, y)→(−x, −y) .
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