Shade Your Hero/Heroine - Unity 4 Game Development - page 209

sign the new parameter to SurfaceOutput o . This parameter will get passed and used
next in the vertex and pixel processor.
We can get more details on Input struct and the default parameter of Sur-
faceOutput struct at http://docs.unity3d.com/Documentation/Components/SL-Sur-
faceShaders.html .
Talking about SurfaceOutput struct , it is the default struct in Unity, which allows
us to pass the parameters easily without creating one.
Tip
SurfaceOutput struct is the default struct in Unity, which is located in the
Lighting.cginc file inside the Unity application. We can also create a custom Sur-
faceOutput struct to pass other variables that are not a part of the default struct by
creating a new SurfaceOutputCustom {…} struct and passing it to the surf()
function like surf (Input IN, inout SurfaceOutputCustom o) .
The tex2D() function will return the color value ( Red , Green , Blue , Alpha ) or
( R , G , B , A ) from the sample state, _MainTex , and the texture coordinate,
IN.uv_MainTex , which we will then assign to o.Albedo and o.Alpha , respect-
ively. The o.Albedo parameter will store the color information (RGB) and the
o.Alpha parameter will store the alpha information.
Note
Albedo, or the reflection coefficient, is defined as the ratio of the reflected radiation from
the surface to the incident radiation upon it. It also refers to the diffuse reflectivity or the
reflecting power of a surface.
More information can be found at http://en.wikipedia.org/wiki/Albedo .
The next line is to get the normal information, which is the vector that contains the posi-
tion ( x , y , and z ). Then, we used the tex2D() function to get the color values (R,G,B,A)
from the sample state, _BumpMap , and the texture coordinates from IN.uv_BumpTex .
Then, we used the UnpackNormal() function to get the normal as the result of the
tex2D() function.