BigDaveDev – Honours

This weeks task is to actually arrive at a research question – by no means an easy task!

I have formulated several possible questions thus far and all are related to the topic of atmospheric scattering, as this is my main topic of interest.  I shall list them below:

• Can atmospheric scattering be used accurately in computer games?
• Is it feasible to include atmospheric scattering in computer games?
• Can post-processed effects – such as atmospheric scattering – be used in computer games without hindering performance?
• Can post-processed effects – such as atmospheric scattering – be used in computer games without negatively affecting overall performance?
• Can atmospheric scattering be implemented efficiently in computer games?
• Can atmospheric scattering be used as an effective depth cue in computer games?
• Can atmospheric scattering be used as an effective enhancement to traditional global illumination models?

While the last one holds the most interest for me, I do not think there is enough time to play with this question as it would involve the use of radiosity, ray tracing or photon mapping.  With that in mind, I feel that the question that will allow me to explore atmospheric scattering and post-processing would be the third-last question:

“Can atmospheric scattering be implemented efficiently in computer games?”

With this particular question, the suggested scope should be small enough to investigate GPGPU techniques and post-processing as well as provide me the choice of using either Preetham or Nishitas’ method for the atmospheric scattering model.

It was also brought to my attention earlier today that using Nishitas’ model would allow an appropriate use of GPGPU techniques as there are lots of variables to compute over several frames.

On a final note then, the research question I am putting forward is:

“Can atmospheric scattering be implemented efficiently in computer games?”

I have installed the CUDA SDK at home and have requested that it be installed in the GameLab at Abertay as well.  Having looked through some of the examples supplied – demonstrating, for example,  real-time ray tracing – I am beginning to understand just how important GPGPU methods could become.  It is clear that harnessing the power of CUDA could be the next stage in game development.

And with the Khronos Group releasing OpenCL in a bid to encapsulate both NVIDIA CUDA and AMD Stream in a similar manner to OpenGL and OpenAL, it is reasonable to expect developers to begin using this in the near future also.

Following are some web-sites to read through to gain a better understanding of CUDA

http://llpanorama.wordpress.com/cuda-tutorial/

http://www.nvidia.com/object/cuda_education.html

http://gpgpu.org/asplos2008

http://gpgpu.org/developer

We were issued a task in class today to complete a worksheet with the aim of guiding us towards a research topic and ultimately a research question.

First I must state the topic of interest.

I have a keen interest in landscape photography and lighting composure is a key aspect in getting the perfect photograph.  In particular, sunset and sunrise are very pleasant effects.  I am interested in mimicking these atmospheric conditions in an interactive environment using post-processing techniques.

Currently the issues surrounding these post-processed effects is efficiency in real-time.  Various post-processing effects are used in Adobe Photoshop and The GIMP, where time isn’t really of the essence.  With atmospheric effects – such as scattering – game programmers and artists have traditionally used rough approximations due to computational expense at the hands of mathematical complexity, leading to less believable – and thus less immersive – environments.  However, these effects are becoming more popular now due to better hardware.

As stated I intend to mimic atmospheric scattering effects by applying it as a post-processed effect.  This principally means taking a screenshot of the framebuffer and attaching it to the depth buffer and applying this texture to a quad the size of the screen.  From here it is passed straight to a pixel/fragment shader where the effects are applied.  I will primarily stick to the methods outlined by Preetham in his 1999 SIGGRAPH paper “A Practical Analytic Model for Daylight” as the techniques he outlines have remained virtually unchanged.

There are two ways to implement these techniques:

1. The traditional CPU and GPU combination
2. The new GPGPU – General Purpose GPU – methods

In this project I will be looking into method 2 using NVIDIAs’ CUDA technology.  Due to lack of access, I will not be able to create an implementation using AMD Stream as I do not have access to a required ATI card.  I would be interested as well in creating a port of this project to a major console – time permitting – such as the PS3 or the XBox360.  However, I doubt there will be much time left over to try and make this port.

The aim of this honours project is to create a visual effect that can be used in games to create stunning and practical depth-cues for vast landscapes.