WHAT THE HECK ARE ALL THESE MAPS IN BLENDER AND 3D MODELING?

Many of you probably already have experience with at least some of the various types of maps in Blender or, Second Life but, for the beginner, all these maps can be very confusing.  I want to spend a few minutes and share my simple explanations of the various maps you may hear tossws about in Second Life or, as it relates to 3D modeling.  Most of my experience has been with texture images but, I have been learning about various maps and their uses in Blender Cycles.  For our purposes, I thought I would share a few of these maps with you.

If you would like precise, in-depth, technical information about the various maps, try searching the Internet and looking at some of the great explanations out there in various places or, Wikipedia has some really great articles which might be of interest to you and have posted a few links at the end of the article in the Resources section.

DIFFUSE MAPS
Most of you may already know what a diffuse maps are even though the name may throw you off a bit.  Simply put, diffuse maps are flat 2D images, which in Second Life we call textures, albeit computer graphics and 3D modeling use the term diffuse maps.  Often, these terms are used interchangeably so don't let the different terms confuse you. These 2D images can be anything from a solid color to photographs which wrap around mesh objects to add color and the illusion of detail rather than adding a bunch of geometry (lots of vertices, faces, and lines) to created mesh objects.

The Second Life's in-world building system provides a set of primitive shapes which are really SL's form of mesh. It is similar to one of those grey or white cubes you when you start up Blender, although Blender allows you to shape or "torture" the primitive shape into more complex objects than Second Life building system.  
  
Second Life Cube on Top of a Blender Created Table

Both objects, in the above image, are rather dull and boring despite how simple or complex their shape turns out to be in the end.  However, when we add a diffuse map or texture to the cube and the table, we turn these bland objects into something much more interesting and realistic.



If you have never ventured in to Second Life before to see the world,or, had experience modeling scene in a 3D modeling package, here are two examples of turning plain objects into life-like objects by applying textures or diffuse maps to objects in-world.

This first image is of my current house and it's surroundings.  Without these diffuse maps placed on this cubes, cylinders, flat objects and more complicated imported mesh shapes, we would see nothing but wooden or dull grey imported shapes, like the deary cube or table above. 

My Second Life Home Exterior with Surrounding Landscaping

Avatars are also mesh and a bit different than our in-world cube.  The greatest difference is our Avatars are "rigged" with a bone structure that allows our avatars  to move (walk, fly, run, jump, stand, etc). Even though our avatars can move, they are still mesh, and just like the textureless cube or table, our avatars require special diffuse maps or "skin" textures to be applied to the our bodies.
Second Life has a unique way of texturing the default avatars in-world through a special layering system.  And, in recent years with the introduction of "rigged" mesh clothing, mesh body creators also have implemented a special layering system for their bodies with what is generally referred to as "Appliers"


My Current Second Life Avatar

I think that anyone creating clothing for classic Avatar bodies, as well as mesh bodies, should be aware of how Second Life's "clothing layering system works".  If you interested, you can find a great article on SL Avatar layers by Seshat Czeret, published April 19, 2009 in her blog article "The Theory of Second Life Skin and Clothing Layers".  While this article may seem ancient to many, it still accurately reflects the laying used of Classic SL Avatars today.  The layering system is also given consideration with mesh avatar bodies when appliers are created.

This article is very useful to understand this layers order when creating tattoos, skins, system clothing and mesh avatar clothing, and skins. http://seshat-czeret.blogspot.com/2009/04/theory-of-second-life-skin-and-clothing.html

Seshat Czeret's Great Illustration of Second Life Skin and Clothing Layers

Almost everything you see in Second Life depends on diffuse or texture maps to give the items a more life-like appearance, adding detail, and realism from the skins for our avatars to make-up, clothing, jewelry etc.  Our houses, furniture, food products, curtains, swords for battle, trees, water, everything is dependent upon the application of diffuse maps or image textures for realism.

UV MAPS
UV maps 3D mesh objects cut apart and laid out flat like a 2D image.  Think of 3D object as flat pattern pieces for sewing a T-shirt or dress. You lay out the flat paper pattern pieces on fabric (your texture), position them appropriately on the fabric, cut out the fabric according to the pattern, and then sew them together to create a whole garment.

Flat Paper Pattern Pieces Laid Out on Fabric for Cutting
 
Another way to think about UV Maps is think of a city, state, or country maps laid out flat showing roads, streets, rivers, points of interest, etc.  The same thing occurs with 3D mesh when we create UV maps.

Google City Map of Paris, France


Many of you probably already know from building in SL, there are 3 coordinates you use to create things...X, Y, & Z...sorta like a East/West, North/South, Up/Down. However, unlike 3D objects, UV maps have only two directions they utilize...X and Y...East/West & North/South. The U coordinate or direction is horizontal or side to side.  The V coordinate or direction is up and down or, in the vertical direction. Notice the orange  squares and rectangles in the lower part of the image below. The top portion represents the 3D object with X, Y, & Z coordinates while the lower portion shows the 2D representation of the object with U & V coordinates.

I created this small wall in Blender to better illustrate what I am speaking about.  I cut the wall apart (the technical term is called unwrapping) and Blender laid it out nice and flat for me in the UV editor window (lower part of the image).  I added a diffuse map (texture image courtesy of Textures.com. See Finding Texture Resources 9.17.2016 article) in the UV editor, so you can see where and how each part of the wall (orange pieces) is laid out or, "mapped" on the diffuse map.


Wall Unwrapped with Each Piece Showing in UV Editor

The technical term for each of your unwrapped pieces (rectangles and squares in this example) is called an island.   Multiple pieces are collectively called islands.  All together, these individual islands make up a UV MAP.

AMBIENT OCCLUSION MAPS
Ambient occlusion maps or, AO maps for short, may be familiar if you are a builder or creator in Second Life.   AO maps are generally black, white, and gray depending on your lighting and are baked (i.e. created) from your unwrapped mesh object. Ambient Occulsion maps is a way to fake shadowing and highlights on mesh clothing and other 3D objects.

The image below (top left) shows a simple dress directly lit in front showing shadows in the folds and other area.  When you flip the garment around where little light hits the back (top right) it is almost solid black.   If you look at the lower left half of the following image, you will see the AO map for this dress...to the right you will see how the dress is unwrapped and placed on a diffuse texture.

Please note, this is am extreme lighting example to show you what AO maps are and how they work in conjunction with UV maps.   The lighting used to create AO maps for SL mesh clothing is much more subtle than this example.

3D Garment Courtesy of Marvelous Designer

To me, AO maps are a shading technique using the internal ambient lighting in Blender or other 3D modeling software.  It makes use of how much light reaches different areas of your mesh object. In the image above, you can see on the red dress that the light varies on the front and is dramatically different on the back where no light reaches it.  Some areas are much darker than others; whereas, some areas are not dark at all.  AO maps add illusion of depth by adding shadows and highlights to to the specific mesh objects they are created for.  

Usually, at least in SL, these AO maps are added to a diffuse texture map in  Photoshop or any graphic software package using a layer based system then the layers are manipulated to create a new composite texture (i.e. using one or more textures to create a new texture).  This manipulation blends both diffuse and ambient occlusion effects into one.  The above is an extreme example of an AO map.  The new composite image is saved as a texture then uploaded to be applied to the mesh object in Second Life. 

NORMAL MAPS
Normal maps are those purplish looking textures which holds X,Y,Z coordinates of your texture as RGB information similar to when sculpties were in vogue in SL before the coming of mesh.  The texture or diffuse map information add additional detail to low poly 3D mesh objects like scratches, bumpiness, dents, indentations, some roundness, etc. and is based on how light would hit those aforementioned detailing.  Using normal maps is just  another way to rich detail without adding additional geometry to our 3D mesh objects and keep them low poly. However, keep in mind, like the AO map, Normal maps adds "fake" detail via your diffuse texture.

Example of Different Normal Maps

Here are 4 examples of Normal maps different normal maps. If you look closely, you will see they are not a solid purple but integrates reds, greens and other colors into the map representing light information, which in turns assists with detail.

Below, I have posted an example of using Normal maps to add detail to our friendly SL cube. Yes, we can add Normal and Specular maps (we will talk about those in a bit) to our mesh in Second Life.  I believe this functionality was added back in 2013, but don't quote me I am so not good with dates! :-)  Can you guess which one of the cubes in the example image has the normal map applied? 



If you guessed the one on the right, then you are absolutely correct.   It's not the best of images but you can see some of the scratches and dings and is it much more shiny and reflective that the cube on the left. 

I am personally have not seen the results of Builders in SL using Normal or Specular maps.  Actually, when I took this shot in SL, I had to fool around with my viewer preferences to see the results, which in turn caused me additional lag. I knew there was a reason why I never notice the usage of them before!  To see this type of detail, you have to enable Atmospheric Shaders, Advanced Lighting Model and Ambient Occlusion to see how they enhance mesh objects.  I believe this is viewer dependent and know that the SL viewer and Firestorm do have these features if you wish to check it out.   

While this is nice detail, you have to have a computer with a graphics card that won't lag you out and keeps on crashing every few minutes. As a creator, you will have to ponder whether using normal maps with your SL creations are worth it to you.  There are advantages in lower poly mesh, cheaper SL uploads, and lower land impact of mesh objects.  But, is your target audience going to actually see the detail?



For more information on using Normal and Specular Maps in Second Life check out this article by Jeremy Linden https://community.secondlife.com/t5/English-Knowledge-Base/Materials-Normal-and-Specular-Mapping/ta-p/2034625
 
SPECULAR MAPS
You may have heard these maps called Specularity or light maps and what they do is add shininess or glossiness to your mesh objects. These maps give makes certain parts of your mesh the illusion of reflecting light. I have posted an example below of a specular map looks like. 

Example of a Specular Map of a Stone Wall
 
RESOURCES
While I hope I have been able to explain in layman's terms about the various types of maps used in 3D modeling, I thought I better supply you with some resources that might explain these subjects better than I can or in more detail. 

Textures & Shaders (Friday, 4 July 2014) By Nathan Wilkie-King on his blog Steps towards my future 
http://nathanwk.blogspot.com/2014/07/textures-and-shaders.html 

Wikipedia (various articles)
https://en.wikipedia.org/wiki/Normal_mapping
https://en.wikipedia.org/wiki/Specularity
https://en.wikipedia.org/wiki/UV_mapping
https://en.wikipedia.org/wiki/Ambient_occlusion 

The Secrets of Realistic Texturing in Blender By Andrew Price on YouTube and Blender Guru


Understanding the Difference between Texture Maps by Eddie Russell, for
Digital-Tutors' Blog 
http://blog.digitaltutors.com/understanding-difference-texture-maps/ 

I hope you find this information of how I currently understand these various, and often confusing, maps used in 3D modeling.  I hope they help you on your journey!

Happy Creating!

Morgaine

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