GPU Pro 4

192 III Image Space

I

0

I

1

I

2

L

k

ω

˙ω

˙ω

Figure 2.3. A flowchart showing how the input buffers get decomposed into a depth

layer: First, the fragments in the input buffers get weighted by ω and ˙ω. The resulting

subdepth layers get alpha-blended to compose the depth layer L

k

. The formula for this

schematics can be found in Equation (2.2).

where z

k−2

to z

k+1

defines anchor points for the layer boundaries. Pseudocode

for how to do matting in a fragment shader is shown in Listing 2.2.

0

1

z

k−2

z

k−1

z

k

z

k+1

ω

k

(z)

z

(a)

0

1

z

k−2

z

k−1

z

k

z

k+1

˙ω

k

(z)

z

(b)

Figure 2.4. The matting functions (a) ω

k

and (b) ˙ω

k

with exemplary anchor points

z

k−2

to z

k+1

.

2. Simulating Partial Occlusion in Post-P ...