What are base bump and top coat bump used for on skin?

I tested the base bump and top coat bump on the skin for Freja at the max 50.

It seems like base bump made her more wrinkled.

The top coat bump is a little more bumpy but seems clearer somehow? Nothing else changed.

I was actually trying to figure out how to make her vascularity show better in renders and thought I'd try to understand bump maps because the products say they come with bump maps, but I really don't know what that means and a search of the topic hasn't revealed anything. I don't want to create a new bump map, I just want to know what I can do with this character's skin, ideally to see veins.

If you could educated me on this or point me to a tutorial, I'd appreciate it.

Note, she does have a STF dirt shell on in these renders so that might affect things too.

The first image shows a base bump at 50 on the right.

The second shows a top coat bump at 50 on the right.

The left image is whatever default skin she comes with.

Freja base bump 50.jpg
2095 x 1019 - 2M
Freja top coat bump.jpg
1431 x 1251 - 2M

Comments

  • margravemargrave Posts: 1,822

    A bump map is exactly what it sounds like: it's a texture that mimics the bumps on human skin.

    Nvidia designed Iray with car manufacturers in mind, and top coat is basically meant to simulate the varnish of car paint, which can have its own bumpiness independent of the bumpiness of the actual fiberglass body. It's not really useful when it comes to human skin.

    Bump mapping is totally irrelevant to seeing veins because veins are under the bumpy layers of skin. To make the veins more prominent, you need to add them to the diffuse translucent or subsurface scattering layers.

  • okay so bump maps make the surface more or less bumpy. 

    I don't know how to add the veins to the other layers, but she has veins in the promo images so I should be able to see them somehow.

  • margravemargrave Posts: 1,822

    If you go to the surfaces tab and click the texture thumbnail, it'll give you the option to open the folder where the textures are. As you can see, the veins are painted onto her texture maps. There's no way to adjust them without taking the textures into a photo editor.

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