Game Development Reference
In-Depth Information
Figure 40 - Multiplicative blend mode.
Each circle has a value of {0.5, 0.5, 0.5}, the intersection portion of the circles is blended
multiplicatively and the result is:
Which is precisely the color value within the intersection.
3.10.5 Screen
To apply the screen blend mode, both the source and destination pixels are inverted then
multiplied and inverted again.
f(a,b) = 1 - (1 - a)(1 - b)
The formula can be further simplified to the form.
f(a,b) = (1 - a)b + a
In this form we can see that the blend state can be set with the blend factors.
ONE, INVSRCCOLOR
Screen lightens the underlying pixels without lightening the darkest areas excessively, it's
similar to an additive blend mode; not as extreme, so it will not produce over lightening
that can occur in additive blend.
