Game Development Reference
In-Depth Information
Objective complete - mini debriefing
In this step, we first added the new properties,
_AmbientColor
,
_SpecularColor
,
and
_Shininess
, which will be used to calculate in our custom lighting models function
to get the specular reflection.
Next, we increased
LOD
to
400
because we wanted to increase the LOD for our custom
lighting model that will calculate the specular lighting.
Next, in the
surf()
function, we changed the first line from
half4 c = tex2D (_
MainTex, IN.uv_MainTex);
to
fixed4 c = tex2D (_MainTex,
IN.uv_MainTex);
to increase the performance of our shader. As the return value from
the
tex2D()
function is the color value (R,G,B,A), which has a range from
0
to
1
, it will
be expensive to use
half
or
float
.
Tip
What are the
half
and
fixed
parameters for? When we are writing a shader in Cg/
HLSL, there are three types of parameters that we can use:
fixed
,
half
, and
float
.
These parameters determine the precision of computations. The parameter
fixed
is low
precision (11 bits, should be in the range of -2.0 to +2.0, and has a precision value of
1/256),
half
is medium precision (16 bits, in the range of -60000 to +60000, and 3.3
decimal digits of precision), and
float
is high precision (32 bits and similar to float on
the computer architecture).
The reference is taken from
http://docs.unity3d.com/Documentation/Components/SL-
However, it follows a trend wherein the more precision we have, the more calculation we
need. If we use
float
every time for our shader, it will cause the game to slow down. So,
if we want to improve the performance of our game, we should use the lowest precision
possible while still having enough output. It's the task of the programmer to decide which
aspects need to be precise and which do not.
Then, in the
surf()
function, we also multiplied
c.rgb
with
_AmbientColor.rgb
and
c.a
with
_AmbientColor.a
, which will get passed to
o.Albedo
and
o.Alpha
,
respectively. This will add the color value from the
_AmbientColor
properties with our
