Final Presentation
- 1. Has the sun set on forward rendering?
- 2. Project Aims Deferred rendering What is it? How does it work? Is it useful? Atmospheric scattering What is it? How does it work? Is it viable?
- 3. Deferred Rendering - What is it? Hargreaves introduced the concept for games in 2005 Flexible rendering system Allows programming of special effects Atmospheric scattering! Used in games like KillZone and Crysis effectively.
- 4. Deferred Rendering - How does it work? Render scene into off-screen buffer Buffer stores info in textures Render full-screen quad Apply textures to quad Add cool effects in pixel shader!
- 5. Deferred Rendering - Is it useful? Short answer - Yes! Long answer... Has issues, like inability to alpha blend Memory bandwidth hogging: I use just two textures for colour and depth -1.83MB Killzone used 4 textures - 9MB! Outweighed by benefits: 50+ lights in one scene Only geometry rendered - no lights Means we can push more triangles per model! Also add really fancy lighting like...
- 6. Atmospheric Scattering - What is it? It is the light interacting with the particles in the air It is the reason we have dramatic sunsets/sunrises Image taken from http://sidramushtaq.wordpress.com/2009/02/
- 7. Atmospheric Scattering - How does it work? Calculate Rayleigh and Mie coefficients for all wavelengths Fire a ray into the scene and find where it intersects the atmosphere. Integrate over this ray to find the optical depth This gives us attenuation due to out-scattering Also adds light through in-scattering Scale the result by the phase function Using angle between camera and sun vectors Result: Blue skies when sun is high Redening of the horizon when sun is setting/rising
- 8. Atmospheric Scattering - Is it viable? Own research has proven only semi-successful Forward rendered version barely runs. Deferred rendering version incomplete. It is very complex to code Must be coded carefully due to nature of equations Crysis includes sky light, but no aerial perspective Perhaps soon the model will be complete?
- 9. Results Deferred Rendering: Very flexible system Works for 3D effects as well! Position can be reconstructed using depth texture Not perfect - alpha blending Forward/Deferred hybrid solution Atmospheric Scattering Own implementation unsuccessful... Very involved system Has been proven to work well in deferred rendering Very realistic - ideal for vast virtual worlds
- 10. Conclusion Deferred rendering is here to stay Most engines support this system More and more games use it KillZone, Crysis, Tabula Rasa and many more Atmospheric scattering remains sparsely used It has been discarded by games in the past Kameo Decision to include this feature must be well thought out It is time consuming to code Almost impossible to debug...
- 11. Questions?