Defining procedural normals in a blending shader

Progg

Hey guys. I've been trying to figure out an issue I am having for a while and haven't come to a solution yet, so I'm turning to the lovely Polycount minds for some insight.

I'll just keep the example simple for convenience sake, but essentially I have a shader that is vertex blending with an edge mask to give a nice procedural like edge. I've done this several different ways before, but I've never actually tried to create what is basically an 'offset' or fake normal for the information that is being created by the blend. I'm not even completely sure if it is possible.

I'm wondering if there is some kind of tech voodoo I can possibly use in conjunction with the expression that is being used to define the alpha of the LERP to essentially create an offset/normal edge distinction between the 2 textures. For example in the attached image, being able to create the illusion in the normal information that the 'brownish' area is sunken into the lighter 'tan' area.

An example of use would be having a chunk of drywall with destruction blended away, and making it appear as though the core behind the wall was recessed.

I can fake an AO shadow around the blended area just fine, I'm just trying to create some kind of lighting illusion to make it appear to not be completely flat.

Thanks!

commander_keen

You could multisample the blending value with a 1 texel offset in 4 directions to derive a normal map.

m4dcow

There is a Material Function that was added awhile back called NormalFromHeightMap and I think it does what commander_keen is talking about.

Ace-Angel

It's pretty expensive mind you.

kodde

I did this with pre-generated textures back in this old project.

Ashaman73

You can use a sobel filter to calculate the normal, thought you need 9 taps into the edge mask texture. When packing the texture in a clever way (ie group 2x2 texels in RGBA channel), then you would only need 4 taps.

JamesWild

Produce a normal map from your edge mask, and sample the edge mask in two places - once to define the edge, and once again to switch from the normal map to a totally flat blue. One moment while I throw together a demonstration.

JamesWild

http://www.smallfiles.org/download/3219/JamesWild_Maskery.upk.html
Here's a package with the material in it. I've just tied it up to a sine from time so you can see it sweeping over the edge map. If you'd like harder edges use ifs instead of blending the normal map.

I'll upload some images in a moment, Imgur are the latest casualty of the "lol let's break our perfectly good website" revolution

JamesWild

Here's how it looks with harder normals: (two different types)

Progg

Thanks guys for all the suggestions. I knew you guys would know what I was talking about.

I'll play around with this later after work, but James that is pretty badass. Exactly what I was talking about judging from the screenshots