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### #Actualchucara

Posted 10 January 2012 - 05:56 PM

Hi,

I have been stuck on this problem for quite some time.. I think it is best described with a picture:

Imagine that this picture is taken of a table. I am able to find the four red dots and their coordinates on the pictures. Same goes for the green dot.

Now, I want to be able to find the location of the green dot in 2D space on the table. Assuming the following mappings:
(171,22) -> (0,0)
(488,155) -> (1,0)
(24,126) -> (0,1)
(361, 346) -> (1,1)

How do I determine what coordinate (167,128) maps to on the plane created by the table?

I seem to have read that I need to find a projection matrix (which I have a basic understanding of what is), but how?

Any hints or suggestions you can give me is very welcome, example calculations even more so.

Also, please point out if I am reinventing the wheel here. I am not aware of any libraries that do this already. (for .NET)

### #2chucara

Posted 10 January 2012 - 05:53 PM

Hi,

I have been stuck on this problem for quite some time.. I think it is best described with a picture:

Imagine that this picture is taken of a table. I am able to find the four red dots and their coordinates on the pictures. Same goes for the green dot.

Now, I want to be able to find the location of the green dot in 2D space on the table. Assuming the following mappings:
(171,22) -> (0,0)
(488,155) -> (1,0)
(24,126) -> (0,1)
(361, 346) -> (1,1)

How do I determine what coordinate (167,128) maps to on the plane created by the table?

I seem to have read that I need to find a projection matrix (which I have a basic understanding of what is), but how?

Also, please point out if I am reinventing the wheel here. I am not aware of any libraries that do this already. (for .NET)

### #1chucara

Posted 10 January 2012 - 05:53 PM

Hi,

I have been stuck on this problem for quite some time.. I think it is best described with a picture:

Imagine that this picture is taken of a table. I am able to find the four red dots and their coordinates on the pictures. Same goes for the green dot.

Now, I want to be able to find the location of the green dot in 2D space on the table. Assuming the following mappings:
(171,22) -> (0,0)
(488,155) -> (1,0)
(24,126) -> (0,1)
(361, 346) -> (1,1)

How do I determine what tcoordinate (167,128) maps to on the plane created by the table?

I seem to have read that I need to find a projection matrix (which I have a basic understanding of what is), but how?

Also, please point out if I am reinventing the wheel here. I am not aware of any libraries that do this already. (for .NET)

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