Thursday, 9 October 2014

About textures and materials (Part 2)

We still have some remaining interesting maps and channels to use in our materials, but theses one are very specific purposes and I won't delve into details for now.

We've have in one hand the displacement or height map. This is can be used with DirectX 11 tessellation to add some extra detail to you models, but actually, in order to use that feature correctly you have to make a correct topology, otherwise, you will have crack on the seams of your models.

Displacement texture
A displacement map of a tileable cobblestone texture
This grayscale map can also used for a very nice material trick called Parallax Occlusion Mapping (POM for short) which is in fact an improvement over normal maps for adding detail that it's not currently modelled on the lowpoly geometry.

Parallax comparison
Comparison when using diffuse, diffuse+normal, diffuse+normal+POM and diffuse+normal+tesselation. 
The emissive map is only used for making materials that have their own light. Very useful for any mesh that currently represents a source of light. Though your material will glow, you still need to add lights to your level in order to illuminate since theses materials don't make any lightning or cast any shadow. Personally when, I do an emissive texture, I do it as a grayscale map, then in the material editor I multiply the mask with a color vector so I can tweak the color of my "light" right in UE4.
Lamp with emissive
Lamps using the emissive channel.
For translucent materials we have also some specific channels available like the opacity which will allow us to control what parts of our material are transparent.
But, if in the other hand we are handling a "masked" material, then our opacity mask will be completely rough (but way cheaper). Don't expect any gradient or transition. Pixels are visible or invisible when using a masked material, there are not middle values of opacity.

Masked material
A simple masked material. 
Right now, there is also an option to make subsurface scattering materials (SSS for short) but on the upcoming 4.5 version of UE this is going to be improved (don't ask me the details, I have to check it out before :P). This is mainly a color texture used to make wax like materials and it tells the material whats the color inside the material so if you are doing an iceberg, this could be something like green teal, or if you attempting to do some human skin, the inner color should be the color of your flesh.

Elemental Demo SSS
A character model from the Elemental Demo using a SSS material.
In this 2 parts article i've been summarising and explaining with my own words what you can actually find in the UE4 documentation page about material inputs. Take a look if you are still confused about this topic or want to delve more about this :)

There is gonna be a part 3 where I'll be explaining what materials are and some example of material webs (Sometimes they get very confusing with all thoses cables..).


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