Pixel motion blur is a post-process effect that blurs pixels based on object velocities to simulate motion blur without needing multiple frame renders. It works by rendering the scene to a texture, calculating a velocity buffer, and using the velocities to blur the final rendered image. However, it has limitations like not handling occlusions properly. Improvements involve using stretched object geometry between frames and iterative sampling over multiple passes. While effective for games, pixel motion blur has challenges for character animation due to vertex shader constant limits.

1. Pixel Motion Blur
http://ozlael.egloos.com

2. Motion blur
• What is motion blur?
– Rapidly moving objects appear to be blurred in
direction of motion
• What causes motion blur?
– In real cameras, film is exposed to moving scene
while shutter is open
• Why do motion blur?
– Adds realism, cinematic look to games
– 24fps with motion blur can look better than 60fps
without

3. Trails behind objects
● Not the same as real motion blur

4. Radial Blur
● 2D Effect

5. Depth-Base Velocity
depth
● For static mesh
velocity

6. Using Accumulation Buffer
● Large time interval between multiple rend
ering

7. Image space (2.5D) motion blur
● Pixel Process Motion Blur

8. Pixel Motion Blur
● Works as a Post Process
● Blurs an image of the scene based on obj
ect velocities
● Not a physically correct but plausible

9. Better than Accumulation Buffer

10. Algorithm
● 1. Render scene to texture
- At current time
● 2. Calculate velocity at each pixel
- Another Buffer
- Calculate current position – previous po
sition
● 3. Render motion blurred scene

11. Velocity

12. Step 1

13. Step 2

14. Step 3

15. What is the Fault?

16. What is the Fault?

17. What are the fault?
● Without knowledge of object edges
● Velocity outside silhouette of object is zer
o(= no blur)
● Solution : Geometry distortion

18. Stretch object geometry

19. Matthias Wloka's trick

20. Matthias Wloka's trick
● stretch object geometry between previous
and current position
● Compare normal direction with motion ve
ctor using dot product
● If normal is pointing in direction of motio
n, transform vertex by current transform,
else transform it by the previous transfor
m
● Not perfect, but it works

21. Matthias Wloka's trick

22. Original Image

23. Stretched Geometry

24. Velocity Visualization

25. Motion Blurred Image

26. Well... Not Perfect
● Not information to avoid occlusion artifact
s
● Number of samples needed depends on a
mount of motion
- 8 samples is good, 16 is better
- Ironically, more samples will reduce fra
me rate, and therefore increase motion m
agnitude

27. Occlusion fault

28. Resolve occlusion
Color Motion
Depth

29. Iterative sampling
● First pass uses 8 samples
● Ping-pong results
● Second pass uses blurred results, this res
ults in 8 * 8 samples (virtually 64)
● 3rd = 512 samples, 4th = 4096, etc

30. Iterative sampling

31. Skinning limitation in DX9
● 256 vertex shader constant registers limit
● Our characters have an average of 54 Mat
rix per drawcall
● For motion blur we need previous frame b
one(Matrix)s transformations
● If Bone == Quaternion & Tlanslation then
must be Uniform Transform
● Or decrease bone count

32. So....?
● In RS3 for Now
● Using Pixel Motion Blur = Only Object’s Tr
ansform
● Animation’s Proceed = Using Accumulatio
n Buffer
● Any suggestion?

33. Reference
● Stupid OpenGL ShaderTricks -Simon Green
● Pixmotor:A Pixel Motion Integrator - Ivan Neulander
● Interactive Real-Time Motion Blur - Matthias M. Wloka & Robert C.
Zeleznik
● Motion Blur Using Geometry and Shading Distortion - Natalya Tata
rchuk, Chris Brennan, John Isidoro
● Pixel Motion Blur - Direct X SDK
● Motion Blur as a Post-Processing Effect - GPU Gems 3
● CrysisNext Gen Effects -TiagoSousa
● Hardware Accelerated Motion Blur Generation -Clement Shimizu, A
mitShesh, BaoquanChen
● Motionblur - Myia
● http://incrysis.com/forums/
● Capcom presentation on Lost Planet