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I have an OpenGL(3.3)+GLEW application. I want to draw a black vertical rectangle at the left side of the window for writing some information on it, like fps (I use GLEW function for drawing text).

I have a common pipeline, like this:

 m_transformation = PersProjTrans * CameraRotateTrans *
           CameraTranslationTrans * TranslationTrans * 
           RotateTrans * ScaleTrans;

I know how it works, but I can't figure out how to draw a projection of the rectangle on the window, like 2d.

I would be glad to any advise.

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You can use an Orthographic projection matrix to transform your vertexes. Then you can simply provide your triangle verts in terms of screen pixels, e.g.: a vertex at (0,0), one at (10, 0) and one at (5, 10).

Here's another reference of OpenGL matrices, with a lot of maths. Make sure to do a search for "OpenGL orthographic projection" and "2D drawing with OpenGL" and you should find a lot of useful information also.

I should also note that to overlay 2D over 3D, you'll have to disable depth testing before drawing the 2D parts. I.e.: glDisable(GL_DEPTH_TEST);.

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