What does this "neutralize mesh verts" example code do?

Development Rendering
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1

I’ve seen this trick used in a few Epic examples.

This first was presented as a way of “collapsing [the mesh vertices] to an infinitely tiny point”, which then helps to achieve the dynamic mesh texture effect the presenter is going for. Source: [GDC 2017, Content-Driven Multipass Rendering, 5:00:40][1]

133388-gdc2017_march1_contentdriven.jpg
133388-gdc2017_march1_contentdriven.jpg1920×1080 197 KB

This second example I found in the Math Hall of the Content Examples project.

133389-m_cameravector_to_object.png
133389-m_cameravector_to_object.png1890×923 223 KB

Both example use the same “subtract Absolute World Position, add Actor Position” trick but I don’t understand how it works, or what it does. Can anyone shed some light on its functionality?

2

Isn’t it for converting calculated final world position to world position offset? Just guessing though.

Regards,

Oskar

3

After tons of meditation I figured it out.

Essentially, - Absolute World Position + Actor Position positions every pixel in the material at the actor’s location; one point.

From there, any offset you apply will be relative to the point at the actor’s location, rather than the pixel’s original location.