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 Getting x and y position from opengl transform  (Read 1834 times) 0 Members and 1 Guest are viewing this topic.
roland
 « Posted 2011-11-27 21:46:03 »

Hi, is there an easy and fast way to get the x and y position from the opengl transform?
for example,
 1  2  3  4  5 `GL11.glLoadIdentity();GL11.glRotatef(45,0,0,1);GL11.glTranslatef(0,10,0);//-> then somehow get x and y position of current transform`

Thanks
Riven
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 « Reply #1 - Posted 2011-11-27 21:58:04 »

Hi, is there an easy and fast way to get the x and y position from the opengl transform?
for example,
 1  2  3  4  5 `GL11.glLoadIdentity();GL11.glRotatef(45,0,0,1);GL11.glTranslatef(0,10,0);//-> then somehow get x and y position of current transform`

Thanks

 1 `glGetFloatv(GL_MODELVIEW_MATRIX, buffer)`

after that, load the 16 values into a matrix class (use the LWJGL one, or google one) and transform your vertex with it.

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roland
 « Reply #2 - Posted 2011-11-27 22:27:21 »

Thanks Riven

How do I transform my vertex with it?
lhkbob

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 « Reply #3 - Posted 2011-11-28 06:52:37 »

Google matrix + vector multiplication.  It's a main component of linear algebra.  The x coordinate of the transform is located at row 0, column 3 and the y is at row 1, column 3.  OpenGL returns the matrix in column major order (so each column is consecutive), which means that x is element 12 and y is element 13 (and z would be 14).

roland
 « Reply #4 - Posted 2011-11-29 04:49:32 »

Thanks lhkbob!

It took me a while to get it, but it works now!
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