Vertex alpha blending (lerp) problem

mianiak

I have a material, t1 lerp t2 mul t3 add t4 vertex alpha. (all on different uv channels from 1 to 4)
I can't get the blending to work right. If I select all vertices and set the vertex alpha to 0, it works, if I select all vertices and set the vertex alpha to 100 it works, if I do a big swipe and select a heap of vertices and set the alpha to 0 it works. But if I select 1 or 2 vertices and set the alpha to 0 nothing happens.
Sometimes also it will do weird things, like blend t2 in some places where the vertex alpha is set to 100. It's almost like it has a mind of its own.

I have been trying to figure out where I went wrong because it was working properly at an earlier stage. I did try using vertex paint modifier, maybe that caused some permanent thing to happen to the mesh. I reset xform, I reset uv xform, but that didn't fix it.

I also used a tool to randomly select vertices so I could get a random type of blend.
http://www.scriptspot.com/3ds-max/scripts/random-selector
But I don't think that could cause a problem, cause all it's doing is selecting vertices. But when I use this tool, the blending works.

Maybe it's cause the mesh is too big? Its the track side grass and its still all one object. Maybe there needs to be a certain percentage of vertices selected for it to work? (which kinda makes some sense, just blending 1 vertices is a bit of a waste :D )
 
Vertex Alpha gets corrupted pretty easily, if you cut up the mesh or weld verts the alpha gets screwed up. The best thing to do is to check tools - mapping channel info, and if the vertex alpha channel has a different number of verts to the rest to just clear it and redo your alpha colouring in.
 
Ahh thankyou!
I see now and I think now I see why I am getting a lot of weird things happening.

I take it these verts values change when different types of mapping is used? ie, map 1 is unwrapped to a spline and has more verts because its more broken up in the uv mapping (map 2 is spline unwrapped too, so in this case it should be the same as map 1) and map 3 & 4 (which should also be the same) are planer unwrapped so they have less verts. Is that right?
trackgrassmapinfo.jpg


Cheers
 
not sure but the actual mapping doesnt get corrupted on export for some reason.
 
Cool, alright that fixed the problem, thanks :)

But now I seem to have realised why lerp isn't used that much, apart from having limited shaders, you need high poly to make it look good.
 
Thank you Alex and Mianiak, I was struggling to realise whata **** was going so wrong with alpha channel, this workaround fix it.
 
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