Scalable Renderer

Description

Real-time renderer built on C++ with scalability features and optimization algorithms for graphics and game engines. It involves LOD generation, time-critical rendering, and visibility preprocessing, among others.

Final project for the UPC course Scalable Rendering for Graphics and Game Engines.

Demo

Dependencies

The following external libraries have been used (all included in the source folder):

• Glut

• GLM

• Eigen 3.3.9

• ImGui

Also, for museum tuning purposes the application Tiled has been used.

How to compile

In the project directory (where all dependencies should be already included) create a build folder and run the cmake command from it:

mkdir build
cd build
cmake ..

Then, compile using the generated Makefile in the same build directory.

make -j

Finally, run the program by executing the generated binary BaseCode:

./BaseCode

How to use

Initial debug information

: If the application seems to be frozen, it is probably performing some computations. The application outputs debug messages in the terminal often so that the user can do a follow-up of which actions are being done.

Setting up the museum

The museum is defined as a .tmx file which can be generated through the Tiled application.
The current file being used can be found in the folder museum inside the source directory. Since the program is parsing the file at this location, it is important to avoid reallocating it. The actual museum file is called tilemap.tmx, and once it is opened in Tiled, one can modify its content easily.
The color map that will appear by default in the editor is shown in the following figure with each value to element correspondence:

Empty	Floor	Origin	Cube
Bunny	Dragon	Frog	Happy
Horse	Lucy	Maxplanck	Moai
Sphere	Tetrahedron	Torus	Armadillo

Setting up the models

All models being used in the current scene are provided in the models folder.
The LOD generation phase can take two paths:

• If the LOD does not exist in disk: Generate from scratch all the LODs using the selected technique.

• If the LOD exists in disk: Read and assign it like an usual mesh.

LOD files are stored in the same models directory, with the following nomenclature:

NAME_REP_CLUST_LOD.ply

Where NAME stands for the original name of the model, REP is the representation technique, which can be average (AVG) or quadric error metrics (QEM), and CLUST is the clustering technique, which can be standard voxel clustering (VOX) or voxel clustering with normal clustering (VOX-NC). LOD indicates the level of the LOD (6,7,8...).
All LODs being used in the current scene are included as well in the models folder, so that loading times are minimized.
If one wants to generate them from scratch, the LOD .ply files should be removed (not the original detailed ones!). If this is the case, I suggest removing only the LODs of a specific object. Otherwise, loading times can be unnecessarily large (1-5 mins in the current system), depending on the combination of techniques being used. In the current scene, this process is highly slowed by the dragon.ply model, since it is much more complex and takes more time to process.

Movement

Standard FPS controls (WASD) with E (up) Q (down). Also, while the space bar is pressed, the camera speed increases.

Visibility

Visibility works similar to the LOD generation phase. Initially, visibility is computed and stored into a file visibility.vis in the same build folder, which is afterwards parsed in the main application. However, in the current implementation visibility computation is included in the application, so it will detect automatically whether there is already a visibility file to use or it should generate a new one. The application does not detect changes in the museum, so if any change in the floor shape is done, the visiblity file should be manually removed.
The visibility computation step can be slightly tuned by the user by modifying the number of rays to use per cell. This can be done in the VisiblityComputer.cpp file by changing the N_RAYS preprocessor macro value. To generate an accurate visibility file I suggest using 20 rays per cell, which takes less than a minute in the current system. Still, I provide a visibility file obtained from using 100 rays per cell, which should be even more accurate. In case one wants to use it, the file needs to be moved manually to the build folder.

Using the GUI

When running the application, a GUI viewport will appear (on top left by default) on the window. By default, the application will take control of the mouse pointer. To recover it, do a left click and the pointer should appear as usual. This is useful to change options from the GUI.
If some options are not fully visible, its size can be extended by dragging the corners.
The available GUI options and their effects on the application are:

• Framerate

• Render points: See points instead of triangles.

• Render wireframe: See wireframe triangles instead of filled triangles.

• Representative computation strategy: LOD representation technique to use per node:

  • Average (AVG)

  • QEM

  Changing this option will reload the scene with the mesh LODs using the selected technique. Notice that if these LODs do not exist in disk, they will be generated from scratch, which may take a significant amount of time depending on the model.

• Vertex clustering strategy: LOD clustering technique to use per node:

  • Voxel clustering (VOX)

  • Voxel with normal clustering (VOX + NC)
    Changing this option may take some additional time because of the same reason stated in the previous point.

• Show colored LODs: from lower to higher LOD: Red, orange, yellow, green.

• Use fixed LODs:

  • If enabled, time-critical rendering will be disabled and all models will have the same LOD, modifiable by the user.

  • If disabled, time-critical rendering will be enabled and the triangles per second (TPS) measure will be displayed as a slider so that the user can manipulate to find appropiate values. Higher TPS values will select higher LODs in general and viceversa.

• Use hysteresis:

  • If disabled, use standard time-critical rendering (notice popping effects)

  • If enabled, two modes will be available:

    • Absolute distance: Individual LOD transitions will be re-allowed after moving closer/further to the object than the defined fixed distance in the slider below (with respect to the distance at the blocking moment between the camera and the object).

    • Relative distance: Individual LOD transitions will be re-allowed after moving closer/further to the object than the ddistance from the node to the the camera scaled by the defined factor below.

    In my opinion, absolute distance is more consistent since relative distance cannot avoid popping if the object is very close at the moment of blocking.

• Use visibility: If not checked, all entities will be rendered and taken into account for time-critical rendering.

• Freeze visibility: To see which nodes are being hidden at a given point, this button can be pressed and visibility will be frozen to that point while the camera can navigate through the museum. A similar test can be done simply by going up (E) and observing that entities from other rooms are not being rendered (since visibility is computed in 2D grid space).