Speed vs velocity channel?

[glacierise]

In the output rollout - we can save speed and velocity channels. Some explanation about that? Sounds redundant on the surface I guess speed is what PhFD uses in the shading process. When do we need these two channels?

[Ivaylo Katev]

speed is a scalar (one component) channel, velocity is vector (3 component) channel. if you have velocity selected, the speed channel is NOT exported, to spare disk space, it is reconstructed from the velocity.
the velocity channel is very used, for PF for example. the speed channel can be used in the shading or PF tests/birth

[vlado]

I guess it's mostly for convenience. The velocity channel takes more RAM and disk space than the speed channel (velocity is a vector, speed is just a number - the magnitude of that vector). So in cases where you don't need the full velocity, but just its magnitude, you can use the speed channel instead.

Best regards,
Vlado

[glacierise]

Ok, that clears it up Thanks!