Game Development Reference
In-Depth Information
Objective Complete - Mini Debriefing
In this step, we irst added the new properies
_AmbientColor
,
e
, and
_Glossiness
,
which will be used to calculate in our custom lighing models funcion to get the
specular relecion.
Next, we increased the
LOD
to
400
because we wanted to increase the
Level of Detail
for our custom lighing model that will calculate the specular lighing. Then we changed
#pragma surface surf
from
Lambert
to
RampSpecular
, which means that we changed
our lighing calculated from the
Lambert
built-in to
RampSpecular
(our custom lighing
funcion,
LightingRampSpecular
).
In the
surf()
funcion, we have changed the irst line from
half4 c = tex2D (_
MainTex, IN.uv_MainTex);
to
fixed4 c = tex2D (_MainTex, IN.uv_MainTex);
to increase the performance of our shader. Also, since the return value from the
tex2D()
funcion 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
.
What are
half
and
fixed
parameters for? When we are wriing a shader
in
Cg/HLSL
, there are three types of the parameter that we can use, which
are
fixed
,
half
, and
float
. These parameters determine the precision of
computaions. The parameter
fixed
is low precision (11 bits, the range of -2.0
to +2.0 and 1/256th precision),
half
is medium precision (16 bits, the range
of -60000 to +60000 and 3.3 decimal digits of precision), and
float
is high
precision (32 bits, similar to the float in regular programming language).
Reference from:
http://unity3d.com/support/documentation/Components/
SL-ShaderPerformance.html
However, it follows a trend wherein the more precision we have, the more
calculaion we need. If we use all
float
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 as possible.
Then, we created our custom lighing funcion, which is
inline half4
LightingRampSpecular (SurfaceOutput s, half3 lightDir, half3
viewDir, half atten)
. This funcion passes four parameters,
SurfaceOutput
,
light
Direction
,
view direction
, and
light attenuation
that we will use to calculate the
output for our shader.
