Embed Size (px)
DESCRIPTION
Motion blur in DX9
Citation preview
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
Trails behind objects
● Not the same as real motion blur
Radial Blur
● 2D Effect
Depth-Base Velocity
● For static mesh
depth
velocity
Using Accumulation Buffer
● Large time interval between multiple rendering
Image space (2.5D) motion blur
● Pixel Process Motion Blur
Pixel Motion Blur
● Works as a Post Process
● Blurs an image of the scene based on object velocities
● Not a physically correct but plausible
Better than Accumulation Buffer
Algorithm
● 1. Render scene to texture
- At current time
● 2. Calculate velocity at each pixel
- Another Buffer
- Calculate current position – previous position
● 3. Render motion blurred scene
Velocity
Step 1
Step 2
Step 3
What is the Fault?
What is the Fault?
What are the fault?
● Without knowledge of object edges
● Velocity outside silhouette of object is zero(= no blur)
● Solution : Geometry distortion
Stretch object geometry
Matthias Wloka's trick
Matthias Wloka's trick
● stretch object geometry between previous and current position
● Compare normal direction with motion vector using dot product
● If normal is pointing in direction of motion, transform vertex by current transform, else transform it by the previous transform
● Not perfect, but it works
Matthias Wloka's trick
Original Image
Stretched Geometry
Velocity Visualization
Motion Blurred Image
Well... Not Perfect
● Not information to avoid occlusion artifacts
● Number of samples needed depends on amount of motion
- 8 samples is good, 16 is better
- Ironically, more samples will reduce frame rate, and therefore increase motion magnitude
Occlusion fault
Resolve occlusion
Color Motion
Depth
Iterative sampling
● First pass uses 8 samples
● Ping-pong results
● Second pass uses blurred results, this results in 8 * 8 samples (virtually 64)
● 3rd = 512 samples, 4th = 4096, etc
Iterative sampling
Skinning limitation in DX9
● 256 vertex shader constant registers limit
● Our characters have an average of 54 Matrix per drawcall
● For motion blur we need previous frame bone(Matrix)s transformations
● If Bone == Quaternion & Tlanslation then must be Uniform Transform
● Or decrease bone count
So....?
● In RS3 for Now
● Using Pixel Motion Blur = Only Object’s Transform
● Animation’s Proceed = Using Accumulation Buffer
● Any suggestion?
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 Tatarchuk, 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, AmitShesh, BaoquanChen
● Motionblur - Myia
● http://incrysis.com/forums/
● Capcom presentation on Lost Planet
