CODEWITHSUNDEEP
opengl3dglsl
Tring Vu
Tring Vu

Reputation: 253

Using GLSL to determine 3D position from mouse click

I was wondering about the problem of getting 3D position from a 2D one. In my application, I got everything set up (mvp matrix, screen position of mouse).

We go from 3D to 2D by the following transform.

gl_Position = projection* view * model * vertex;

Then these clip coordinates are divided by w to NDC, and then converted to screen coordinates. I want to do the reverse (mouse click to 3D). Screen to NDC is easy for x and y. But there is a loss of z data.

As far as I can tell, the ONLY method to recover the 3D data is using ray-casting with a tree based spatial data structure and maybe CUDA/OpenCL. But I am not sure. Is there any other way? Is there a method to recover 3D position given that we have the MVP matrix and screen coordinates?

Upvotes: 1

Views: 409

Answers (1)

datenwolf
datenwolf

Reputation: 162164

Read the deph value at the mouse pointer position (glReadPixels(…, GL_DEPTH,…)) and use that for recovering Z. Or do the raycasting into a scene structure. Depending on your applications either one may be the better solution.

Upvotes: 1

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