HELP with weathered concrete slabs

Hello everyone,

So this is basically a dividing wall in an unnamed country. I’m trying to weather the tops of the concrete slabs. I’m using the procedural leak/spill here. I’m trying to make the leak/spill i.e. the white paint-like weathering START at the top of each slab instead of being plastered across the whole row of slabs like they’re a contiguous wall. Not sure how to do this. Snapping, perhaps? Really too new to blender to know. Help?

I’m having a hard time understanding your problem, perhaps you could rephrase it? As I see it, weathering does start at the top? By “top”, do you mean the top edge of the vertical plane, or the parts of the wall facing the sky?

Currently the white stuff is starting at the red line like so:

I want it to start at the top of each slab like this:

And I should mention that each slab of the wall is an island.

each slab as an island:

I’m trying to exclusively use shader graph here and nodes that both eevee and cycles use.

Does the mesh actually extend to the red line, and it is just transparent there (before the weathering)?

No, it’s not transparent there, it’s just where the texture approximately starts from.

Here’s the geometry in Edit Mode.

Try disconnecting the output of the node graph from the “volume” input of the material output node.

It’s on the Surface input, not Volume…

…not sure what in the world it is that’s going on, really.

Are you positive that it’s not connected to the volume input of the affected object? If it’s only on the surface input, it should not be drawing anything beyond the boundary. I’d need to see the blend file to make any meaningful suggestions.

Can you download this link? Kind of terrified of what you’ll think of how messy this thing is.

Re the volume input thing, it’s definitely not connected, but I may not have been as specific as I could be; I have a group of slabs as part of one mesh object. Not sure if this is what I should be doing, but I can’t think of a better way to get the graffiti pieces to be continuous across each piece of the wall.

I don’t see the effect you’re describing, weathering starts at the edge of each slab both in eevee and in cycles. None of your pictures show it either.

Okay, I’m not sure why I didn’t see that. Thanks regardless Eugene I don’t think I would’ve seen it otherwise.

@Eugene_Kuznetsov it’s subtle, but it’s definitely there. This is what it looks like prior to separating by loose parts:

This is what it looks like after separating by loose parts:

I can deal with it being like this, it doesn’t inherently screw up my workflow: it’s just that I’m going to have literally thousands of these slabs in my scene, and ugh to that, as opposed to only several sections of wall

Still don’t see it. Not even a subtle effect. This is the same wall section (I had to drop in some random textures to replace the ones used by the scene):

@Eugene_Kuznetsov This doesn’t make it any clearer, does it?

You see the black paint splatter, it’s all centered at the same height in space, which is NOT what I want. It should be at a fixed point above the center of the slab, i.e. RELATIVE TO the slab’s xyz coordinate. I do get what I want when I turn every slab into a different object, using Separate By Loose Parts, as below:

BEFORE:

AFTER:

…but I’m wondering if there’s a way for me to get that same effect without resorting to that. I don’t want to turn every slab into an individual object, I want to use the Shader graph to say “start the paint splatter at height H and end it at 3H/4” using the individual height H of that slab. Does that make any sense?