[Pharo-project] simple point function seems strange
Hi (10@20) rotateBy: #left centerAt: 0 @0 returns 20@ -10 and my math tells me that this is a rotation to the right. Am I correct? Then why I'm wrong? screen coordinates vs. math coordinate? Stef
2010/7/8 Stéphane Ducasse <stephane.ducasse@inria.fr>
Hi
(10@20) rotateBy: #left centerAt: 0 @0 returns 20@ -10
and my math tells me that this is a rotation to the right.
Am I correct? Then why I'm wrong? screen coordinates vs. math coordinate?
Sure.
Stef
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On 08.07.2010 00:11, Stéphane Ducasse wrote:
Hi
(10@20) rotateBy: #left centerAt: 0 @0 returns 20@ -10
and my math tells me that this is a rotation to the right.
Am I correct? Then why I'm wrong? screen coordinates vs. math coordinate?
Stef You rotate around the center, left is compared to the center -> point vector, not the other way around.
Cheers, Henry
On 08.07.2010 00:26, Henrik Sperre Johansen wrote:
On 08.07.2010 00:11, Stéphane Ducasse wrote:
Hi
(10@20) rotateBy: #left centerAt: 0 @0 returns 20@ -10
and my math tells me that this is a rotation to the right.
Am I correct? Then why I'm wrong? screen coordinates vs. math coordinate?
Stef You rotate around the center, left is compared to the center -> point vector, not the other way around.
Cheers, Henry ... assuming you use screen coordinates of course, starting at top left :)
I was stupid to think that the rotation did not depend on the origin and coordinate system. Stef On Jul 8, 2010, at 12:28 AM, Henrik Sperre Johansen wrote:
On 08.07.2010 00:26, Henrik Sperre Johansen wrote:
On 08.07.2010 00:11, Stéphane Ducasse wrote:
Hi
(10@20) rotateBy: #left centerAt: 0 @0 returns 20@ -10
and my math tells me that this is a rotation to the right.
Am I correct? Then why I'm wrong? screen coordinates vs. math coordinate?
Stef You rotate around the center, left is compared to the center -> point vector, not the other way around.
yes but
Cheers, Henry
... assuming you use screen coordinates of course, starting at top left :)
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participants (3)
-
Henrik Sperre Johansen -
Nicolas Cellier -
Stéphane Ducasse