Metallic vs Specular

With technology and the advancement of lighting/shaders comes new ways to do what was used in the past. Real time rendering has gone from no polygons, to flat shaded polygons, to shaded polygons to shaders and materials together. As tech gets better, more options open to developers in making things more accurate.

Take for example the specular map, which comprises of a black and white image where white is the most reflective and black has no reflection.

Left : No specular Right: full specular

As you can see, specular allows for a surface to have a reflection value. Variation of how much light is reflected is in the lightness and darkness of the spec map. 

This has been the most common method for most 3D software and game engines to render. 

There is a problem though, it lacks proper variance control. Objects are either smooth or rough, flat or reflective and sometimes a mix of both. Take a car that has been in the junkyard for too long for example, the paint would have a reflection (provided it was a glossy paint), the metal will have its own reflection which might not be as bright as the paint, then the metal may be work or have rust that eats away the overall shine. This is an example of layers of variance. Specular is useful for this, but when it comes to more accurate reflection and object roughness, the metallic layer is the direction to go and has now become the standard for real-time graphics developers

A roughness layer from shiny to dull.

A metallic layer from 0-1

So the question is, can a metallic and roughness layer mimic a specular?

The answer is yes.

In fact, developers that are finding the value in metallic/roughness are now preferring it to specular/gloss. 

http://forum.unity3d.com/threads/official-specular-vs-metallic-workflow.274612/

Disney use and prefer physically based rendering and metallic/roughness to their older methods due to the accuracy it provides. 

https://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf

Unreal Engine 4, Unity, Frostbite Engine, Fox Engine and many other modern engines have now moved on to this method. Technology moves and everyone should move with it. 

More on Physically Based Rendering.

Tutorial: Physically Based Rendering, And You Can Too!

Here is an excellent breakdown on physically based rendering that goes through a series of materials and surfaces that will greatly effect how a 3D model will look under lighting conditions, from rough rubber to shining metal.

Tutorial: PBR Texture Conversion

Here is the tutorial on the same page that highlights what went into creating the materials

Imperfections for perfection.

A quick set of tips for creating photogrammetric game ready assets in Unreal Engine 4

Imperfection for Perfection.

Modern game engine breakdown.

Here is an excellent breakdown of all the layers of a modern graphic engine, in this case the engine used for Grand Theft Auto 5 : The Rockstar Advanced Game Engine.

Silly name, unbelievable engine, considering it was designed to run on gaming consoles that had only 512mb of ram or in Playstation 3's case 2x split 256mb ram, this is a very well implemented engine that showcases what can be done with limitations.


Grand Theft Auto 5: Game engine breakdown

Small teams, big projects

When 3D animators get together in small teams, it may not seem possible or much harder to produce something as amazing as say, Pixar or Dreamworks. Every now and then though a small studio can show that they are very capable.

Just remember, dreaming big should not be limited by small teams.

Render target

                            Here is a render target mocked up with a few layers of a scene:

This render consists of; colour map, diffuse map, specular map, environment map, a pre-made vignette filter, explosion effect, dust layer and scratch layer.

By adding all the parts together, I can quickly test how the layers can be used, arranged and approved upon. Some post processing such as motion blur will be added in compositing as it is too  time consuming to add in the layers when rendering. 

Handy Maya tutorials

 Found a large selection of handy mini tutorials and full explanations for Maya.


Take a quick look.