Switch rendering to OpenGL 3.3 (or later) specifications

[bkloppenborg]

At present most of SIMTOI uses the old 1.20 OpenGL pipeline and renders models in a very inefficient fashion. These should probably be evaluated and upgraded to modern specifications.

The current immediate mode rendering leads to very poor performance as noted in #70.

[bkloppenborg]

Further investigation of #70 showed that the rendering itself was exceptionally slow. Therefore I re-implemented the concentric ring disk model in OpenGL 3.2 using GLFW and GLEW using VBOs and element arrays. SIMTOI can render the model at a rate of ~22 frames per second. This new implementation does ~450 fps on my NVidia 8600m GT laptop. This acceleration, ~21 times, justifies switching from immediate mode rendering which is presently in SIMTOI to vertex buffers.

Doing this switch will require an almost complete rewrite of all of the OpenGL-related code including CWorkerThread, all models, and all shaders. After inspecting the code, here is a list of things needing to be changed:

Core program

• CGLWidget will need to be created with an OpenGL 3.2+ CORE context
• Introduce dependency on GLM, add FindGLM.cmake script.

CWorkerThread:

• glMatrixMode is deprecated. All model transformations will need to be done otherwise.
• glOrtho is deprecated. This can be replaced by a projection matrix using glm::ortho(...)

CModel:

• Remove color function. Include the color in with the vertex array buffer
• Replace Rotate() with function that returns glm::mat4 rotation matrix (Properly formatted for astrophysics conventions of course.)
• Remove SetupMatrix. The model matrix can be replaced by the identity matrix, glm::mat4. This should probably be handled in the model's render function as we do nothing special here.
• Replace Translate with a function that returns a glm::mat3

CShader

• The entire class will need to be reworked to conform to OpenGL 3.2 specs.
• Remove the min_xyz uniform from being a required variable.
• Add method to get a pointer to the program object so parameters may be queried by the models.

[bkloppenborg]

All of the above items have been completed. Almost all models have been ported to OpenGL 3.2 CORE as of 8dea6bfaff393ceed27ec95737ef0390f53f4556. Rendering tests with the Pascucci disk model are very promising:

Direct rendering mode with Pascucci disk model.
Completed 3 iterations in 41.413 seconds.
Throughput: 0.072441 iterations/second.

That is, 15.1 FPS. The VBO-based model

VBO rendering mode with Pascucci disk model:
Completed 9 iterations in 23.361 seconds.
Throughput: 0.385257 iterations/second.

That is, 80.5 FPS. This is a speed up of ~5.3 times for a model of the same complexity.

[bkloppenborg]

All changed completed by commit 931a725.