environment matting and compositing
DESCRIPTION
Environment Matting and Compositing. CS 395 – Advanced GraphicsPresented by Jay Hetler Douglas E. Zongker ~ Dawn M. Werner ~ Brian Curless ~ David H. Salsin. What is Matting? Extracting the foreground image from the background Describing the opacity of the foreground at every point. - PowerPoint PPT PresentationTRANSCRIPT
Environment Matting and Compositing
CS 395 – Advanced Graphics Presented by Jay Hetler
Douglas E. Zongker ~ Dawn M. Werner ~ Brian Curless ~ David H. Salsin
What is Matting?•Extracting the foreground image from the background•Describing the opacity of the foreground at every point
What is Compositing?•Holding back the part of the new background that theforeground blocks.•Placing the foreground element in a new background
Original Uses
Weather Reports Cinema Special Effects
Matting Equation
C = F + (1- )B
• C ~ Color• F ~ Foreground color• B ~ Background color• ~ Amount of light that passes through the
foreground
How difficult is Matting?
Matte Image
Good Results?
Problems with Matting
Images do not look realistic
• Lack of Refracted Light
• Lack of Reflected Light
Solution:Modify the Matting Equation
Environment Matting Equation
C = F + (1- )B + • C ~ Color• F ~ Foreground color• B ~ Background color• ~ Amount of light that passes through the
foreground• ~ Contribution of light from Environment
that travels through the object
Explanation of
= R M(T , A )R ~ Reflectance coefficient
M ~ Texture mapping operator
for axis-aligned rectangle (A)
of texture (T)
i = 1i i i
m
Environment Mattes
Performance
• Calibration
• Matting: 10-20 minutes extraction time for each texture map (Pentium II 400Mhz)
• Compositing: 4-40 frames per second
• Real-Time?
How much better is Environment Matting?
Alpha Matte Environment Matte Photograph
How much better is Environment Matting?
Alpha Matte Environment Matte Photograph
Movies!
Importance of Sidedrops
Light comes from other parts of the environment
Sidedrop Example
Sidedrop x2
Failure Cases
Box-filter Gaussian-weighted Photograph
Failure Cases
Composite Photograph
Failure of Engineering
Failure of Theory
Next Steps
• Depth
• Accuracy
• Real-Time Capture
Progress?Depth Accuracy
No Real-Time