Blog 3 

This week in INFR2350, we covered global illumination and shadow mapping in our lectures, and color manipulation in tutorials.

Global illumination is a more advanced lighting technique that takes into account the addition of reflected rays. It tries to simulate real-world lighting of having rays of light bounce off surfaces indefinitely. This of course comes with the cost of speed. While there are many varieties of techniques, such as radiosity and ray tracing, screen space ambient occlusion or SSAO is the most suitable for games. (at least until hardware improves further). SSAO is implemented in the pixel shader using the depth buffer to sample the rendered texture(first pass) of the screen. Using the surrounding pixels of a given point, occlusion is computed. Essentially, soft shadows are added to up the realism of the game.

Notice how the objects on the table are almost popping out of the image, almost like they are not actually on the table. 

In this second image, with ambient occlusion, the objects blend in with the shadows and feel consistent as part of the scene.

The other topic, which too lend to creating more realistic environments is shadow mapping. As the name implies, shadow mapping creates the appearance of shadows in game. As global illumination, there are many techniques to create them. The basic concept of shadow mapping requires to passes like SSAO, firstly the scene is partially rendered from the perspective of the light source(per light); only objects casting a shadow are rendered. The only thing needed from this pass is the depth. The data of the depth buffer is saved and used as the shadow map for the second pass. In the second pass, the scene is rendered from the perspective of the camera. The depth map from the first pass is then used to compare each pixel with to determine whether the given pixel is in shadow or out of shadow. 

A flaw with this technique is the visual artifacts of jagged shadows can be created due to the limitations of pixels mapping to texels. A simple solution is to blur or anti-alias the shadow. 

An example can be seen here:

Development Progress

Forgive the short length of this update, as my excellent time management skills have led to a drought of time; having to hectic challenge of completing 2 lengthy assignments.

Speaking of which, In animation and production we are to prototype a cutscene rendered in Maya and edited with Adobe Premier. This brings in to the question of how to implement this cut scene into our game. Browsing through the annals of the internet, the methods differ by either having the scene scripted in game and playing it in real time(quite challenging and redundant), or playback a prerendered video.  I am opting for the latter, though we would need to delve deep into Maya.This limits the option of integrating video playback with OpenGl/SFML, or an external library. Another perhaps more interesting option would be to playback the cutscene as a sequence of images on a texture.

Development for our game is advancing along bit by bit. The conversion to modern OpenGl is progressing; the primary concerns of VBOs and shaders are integrated and ready for use.  Transitioning away from old OpenGL perspective and transformations is another matter however… It requires overhauling our previous camera system and math libraries.

Hogue, A. (2014, February 3). Global Illumination [PowerPoint slides].

Retrieved from UOIT College Blackboard site: https://uoit.blackboard.com/

SGHi. (2011). Skyrim - NVIDIA Ambient Occlusion [Screenshot]. Retrieved from http://www.nexusmods.com/skyrim/mods/31/?

Shastry, A, S. (2005). Soft edge shadow comparison [Screenshot]. Retrieved from http://www.gamedev.net/page/resources/_/technical/graphics-programming-and-theory/soft-edged-shadows-r2193