# OpenGL How this can done in OpenGL? [video example]

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Here is one video. http://www.youtube.com/watch?v=cmcnIWN6y2Y There is a textured grid. Grid is fixed size, each cell has it's own X,Y value. If user presses mouse button and drags mouse there is blocks (with size 64x64) drawn on the grid!! I have actually this grid, each block has fixed size (64x64), there is 256*256 (width*height) of them (this is grid max size). Is there anything general (algo, example, book) that helps me achieve that? I make a grid, and when dragging with mouse i draw blocks at mouse cursor. And i need this in OpenGL. I know that i must translate screen coords to world coords. OK, but how to draw blocks at mouse. One such block (minimum) always must be there. With mouse user can draw them more. And i have this example: But it doesnt draw cubes, but planes on grid. "From 2d to 3d in opengl, opengl coordinates tutorial" http://www.og.delcode.com/ Any help with that?

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The technical knowledge it takes to do this is not so vast that it is out of the reach of a new programmer, however, it does take some understanding of linear algebra.

To briefly sum it up, the method used involves taking the 2d position of the mouse on the screen and using the view matrix to generate a ray. This ray, as it moves, creates a cuboid.

If you want to get into this the first thing you need to do is to learn about linear algebra, in particular, how matrices and vectors are used in 3D rendering.

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Thanks for reply. Im willing to learn anything that is needed to finish my project.

But mainly im like hacker. Im hacking code together until it starts working and works for me. So far this approach worked for me. Somehow im learning like that.

It's 03:15 A and im not sleeping. I just (hacked) solved this problem
http://www.gamedev.net/community/forums/topic.asp?topic_id=528945

This was indeed memory allocation problem. Allocated enough and works fine.

Thanks Brother Bob.

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hi,
the video looks verry good,
perhaps this links can you help:
-> MayaCamera & FloatyCamera
i dont know whats your os is: (linux & win)

http://www.cis.njit.edu/~nichol/courses/it360/

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But i don't have problems with camera or rotation. I solved them.

I have problems figuring out how to draw boxes with mouse in 3D.
Like in video.

I need more sources related to drawing with mouse, ray picking and so on.

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