Thanks @mhagain, I needed such a post to compare D3D9 and OpenGL 2.1, as I'm using render to texture, instancing and I'm using dynamic vertex buffers to update my "matrix buffer" used for instancing in D3D.
The reason I'm trying to add OpenGL renderer is to be able to port my applications for Mac and Linux, but more importantly I thought I can make a Web based renderer via WebGL, but I have zero understanding of how a desktop OpenGL simple engine( let's say OGL 2.1) could be  ported to WebGL and the user provided with an URL to play applications build with it.

Thanks @mhagain, I needed such a post to compare D3D9 and OpenGL 2.1, as I'm using render to texture, instancing and I'm using dynamic vertex buffers to update my "matrix buffer" used for instancing in D3D.

The reason I'm trying to add OpenGL renderer is to be able to port my applications for Mac and Linux, but more importantly I thought I can make a Web based renderer via WebGL, but I have zero understanding of how a desktop OpenGL application ( let's say OGL 2.1) could be  ported to WebGL and the user provided with an URL to play it.