Vertex Color VS UV channel to store vertices data

Development Rendering
1

Hi all,
I have a question for you about a material I’m workin on.
I must store in my meshes a couple of float values for each vertex and use them in the material to drive some stuff.
At the moment I have 2 ideas, both needs a DCC software workaround before importing into UE4:

1- Use vertex color (for example R and G channel) to store this values and in UE use a VertexColor node in the material to retrieve them
2- Add a new UV channel and place vertices in specific position of the UV space, then access the values with a TextCoord node.

My question is: are both method comparable in terms of performance/memory usage or is one better than the other?
Almost every, big mesh of the level should use this feature.

At a first glance I’m oriented to the vertex color solution, but I’m not so sure :slight_smile:

Thanks a lot in advance

Daniele

2

you should use VertexColors then, since they do not add any cost ontop of your performance (They are part of the existing Vertex Data). Using another UVChannel would mean adding a new DrawCall to your rendering. Which reduces performance.

3

Yes, I suppose you’re right: an extra draw all is surely more expansive :slight_smile:
But does the added channel cost 1 draw call even if I don’t use it for a texture? (but just read it for other purpose).
And what about additional channels not used at all in a material?

Sorry for my question shooting :slight_smile:

Thanks!