Timeline for Is the statement in Scratchapixel about transforming points correct?
Current License: CC BY-SA 3.0
8 events
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| Jun 29, 2015 at 18:46 | vote | accept | BRabbit27 | ||
| Jun 29, 2015 at 17:50 | answer | added | Alexandre Desbiens | timeline score: 1 | |
| Jun 29, 2015 at 17:12 | comment | added | Alexandre Desbiens |
But how do we convert a point or vertex from one coordinate system (such as the world coordinate space) to another [...]? This part seems to imply that in that paragraph, they inverted A and B so that A is world coordinates and B is local coordinates, to show how to convert world position to local position.
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| Jun 29, 2015 at 17:06 | comment | added | BRabbit27 |
The texts passages are the two I quoted in my question. To me the example says Pworld = Plocal * M which is ok to me. However, the text quoted, seems (at least for me) saying Pworld = Plocal * inv(M), i.e. "If we transform a point P whose coords are defined w.r.t. to local-coord system with the inverse of M, we get the coords of P w.r.t. world-coord system" or paraphrasing "A point P in local-coord system, transformed with the inverse of M, gives the point P in woord-coord system". I think it should be "A point P in local-coord sys, transformed with M, gives the point P in woord-coord sys"
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| Jun 29, 2015 at 17:02 | review | Close votes | |||
| Jul 14, 2015 at 3:04 | |||||
| Jun 29, 2015 at 16:54 | comment | added | Alexandre Desbiens | Could you put a quote of the text passages you find confusing? Maybe, like you said, it's the wording, so someone here could formulate it with a different approach. | |
| Jun 29, 2015 at 16:50 | comment | added | Alexandre Desbiens |
If M transforms from local to world, then pLocal * M = pWorld and pWorld * inv(M) = pLocal. These are the formulas stated on the page you linked.
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| Jun 29, 2015 at 16:43 | history | asked | BRabbit27 | CC BY-SA 3.0 |