Unity可编程管线的顶点光照Shader

UnityCG.cginc有一个叫ShadeVertexLightsFull的函数可以用来计算顶点光照。

源码如下：

// Used in Vertex pass: Calculates diffuse lighting from lightCount lights. Specifying true to spotLight is more expensive

// to calculate but lights are treated as spot lights otherwise they are treated as point lights.

float3 ShadeVertexLightsFull (float4 vertex, float3 normal, int lightCount, bool spotLight)

{

float3 viewpos = UnityObjectToViewPos (vertex);

float3 viewN = normalize (mul ((float3x3)UNITY_MATRIX_IT_MV, normal));

float3 lightColor = UNITY_LIGHTMODEL_AMBIENT.xyz;

for (int i = 0; i < lightCount; i++) {

float3 toLight = unity_LightPosition[i].xyz - viewpos.xyz * unity_LightPosition[i].w;

float lengthSq = dot(toLight, toLight);

// don't produce NaNs if some vertex position overlaps with the light

lengthSq = max(lengthSq, 0.000001);

toLight *= rsqrt(lengthSq);

float atten = 1.0 / (1.0 + lengthSq * unity_LightAtten[i].z);

if (spotLight)

{

float rho = max (0, dot(toLight, unity_SpotDirection[i].xyz));

float spotAtt = (rho - unity_LightAtten[i].x) * unity_LightAtten[i].y;

atten *= saturate(spotAtt);

}

float diff = max (0, dot (viewN, toLight));

lightColor += unity_LightColor[i].rgb * (diff * atten);

}

return lightColor;

}

 

代码中使用了unity_LightPosition等Unity的预制变量，这些变量只在Vertex Pass中可以使用。在Pass的Tags中设置"LightMode" = "Vertex"来激活Vertex Pass，否则这些预制变量不生效。

参考文献

https://docs.unity3d.com/Manual/SL-UnityShaderVariables.html

https://gist.github.com/aras-p/4175727