What to learn

Hello everyone.
I'd like to know what should I learn to be able to make an application like Seamless 3D.
Consider I'd like it to run on mobile and desktop (Windows, Linux and Mac, iOS, Android) so the language of choice would be C#/Xamarin or C++/Qt.
Then, I'd also learn OpenGL ES as graphic API.
Beside this, what else should I learn? Please, list thoroughly.

Hi Powerfull, I found the QT OpenGL examples useful but what I really wanted was an example of some coloured triangles that used normals. Simple online examples of WebGL helped me figure out how to do this as WebGL uses OpenGL ES. I have a simple program using QT that uses some of the classes I developed for seamless but is kept to just a few short files to keep it simple making it ideal for me when testing things out with a new compiler or operating system. It can not open files containing nurbs patches like the QT version of seamless can, it can only open a file containing a low level mesh of coloured triangles with normals (and render it and lets the user orientate the view) but will be helpful for someone wanting to learn about the inner workings of seamless or 3d rendering in general.

You MUST use shaders in whatever OpenGL app. If you don't,you'll end up with white triangles.
Please, let me have a look at your development version

Yes scripts written in the OpenGL Shading Language are used for specifying the colours in the vertices.

I have just uploaded my port to Qt which you can download from this page: http://www.seamless3d.com/qt/

Sadly it takes me a lot of time publishing files, it's not a simple matter of just uploading where I am up to. When experimenting I end up with a number of variations and so I have to verify what I upload is in working order and compatible with the example smls files and I have to verify that my instructions work for what I have uploaded, so there is a lot of uploading and downloading, waiting for the compiler to compile everything from scratch and rebooting to a different operating system to verify what I have got working in one OS works for the rest. The files I have uploaded seem to compile reliably for Linux and Windows but I seem to be getting random results (as in failing or succeeding to generate an APK file) still when I compile for Android when starting from scratch. Been stuck on this for days now. I suspect I may not have something set correctly in the Qt pro files or I may be just making a lot of silly mistakes from the stress, like forgetting to delete something or gotten confused which file is which, easy for me with all my variations. It would be nice to know what results you get from the uploaded files.
best wishes