Nov 26, 2009

Screen-space buzz survey

This post exposes a survey of screen-space methods proposed in the field of CG. I will not go into the details of these methods since that is not the purpose of this post but I invite you to read these articles since, to my opinion, they are very interesting.

Screen-space ambient occlusion

Many methods have been proposed to render ambient occlusion. The one proposed by Crytek in 2007 became very popular and was named “Screen-Space Ambient Occlusion”. The method was designed to be used in real time in Crysis game. To my opinion, the real first paper to propose screen space ambient occlusion was proposed by Luft et al.: Image Enhancement by Unsharp Masking the Depth Buffer. Then, a High quality (but slower) version was proposed by Louis Bavoil et Miguel Sainz (nVidia).
It is interesting to note that the screen-space name became more and more popular and started some kind of Buzz! Also, it seems that screen-space and image-space are synonyms. Am I correct?

For more links on screen-space ambient-occlusion please refer to this wikipedia article
. Also, many methods have been published in ShaderX7.

Screen-space global illumination

Crytek also proposed a screen-space global illumination method. However, I am not aware of the algorithms they use. I suppose it is a variant of their SSAO using sampled surfaces color as well as its normal direction in order to take into account relative surfaces orientation (refer to their presentation about light propagation volume).
Also, researchers proposed the screen-space directional occlusion method to compute real time global illumination.

Screen-space fluid and water

Even fluid got screen-spac-ed!
Concerning SPH fluid simulation, two methods have been proposed as an alternative to marching-cube-like methods, namely : Screen-Space Meshes
and Screen-Space Fluids Rendering with Curvature Flow.
To render ocean, a screen-space grid projection is used in the Cry Engine
. Another screen-space approach has also been proposed on gamedev with really nice looking results.

Screen-space light shaft

One article about this in GPU Gems 3. Ok they used the word post-process but after reading the article, it sounds a lot like screen-space to me!
It seems that Crytek uses a similar methods. Obviously, they really love screen-space methods! :). I agree with them since the methods they use are fast and result in eye-candy effects!

Image-space sub surface scattering

And last but not the least, Image-Space Subsurface Scattering for Interactive Rendering of Deformable Translucent Objects.


Wouhaou! So many screen-space methods! I wonder what’s next… Also, you can read this other interesting discussion I have found here to complete this survey.

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