Cg 编程/Unity/双面表面
本教程涵盖了双面每顶点照明。
它是关于 Unity 中基础照明的系列教程的一部分。在本教程中，我们扩展了“镜面高光”部分以渲染双面表面。如果您还没有阅读“镜面高光”部分，现在是阅读的好时机。
正如代数曲面图所示，有时需要对曲面的两侧应用不同的颜色。在“截面”部分中，我们看到了如何使用正面剔除和背面剔除的两个通道来对网格的两侧应用不同的着色器。我们将在本教程中应用相同的策略。
正如在“截面”部分中提到的，Cg 中的另一种方法是使用一个语义为 VFACE 的片段输入参数来区分两个侧面，请参阅Unity 的着色器语义文档.
双面每顶点照明的着色器代码是对“镜面高光”部分中代码的直接扩展。它需要两组材质参数（正面和背面），并复制所有通道 - 一份带有正面剔除，另一份带有背面剔除。这两个副本的着色器是相同的，除了背面着色器使用反转的表面法线向量和背面材质的属性。
Shader "Cg two-sided per-vertex lighting" {
Properties {
_Color ("Front Material Diffuse Color", Color) = (1,1,1,1)
_SpecColor ("Front Material Specular Color", Color) = (1,1,1,1)
_Shininess ("Front Material Shininess", Float) = 10
_BackColor ("Back Material Diffuse Color", Color) = (1,1,1,1)
_BackSpecColor ("Back Material Specular Color", Color)
= (1,1,1,1)
_BackShininess ("Back Material Shininess", Float) = 10
}
SubShader {
Pass {
Tags { "LightMode" = "ForwardBase" }
// pass for ambient light and first light source
Cull Back // render only front faces
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
// User-specified properties
uniform float4 _Color;
uniform float4 _SpecColor;
uniform float _Shininess;
uniform float4 _BackColor;
uniform float4 _BackSpecColor;
uniform float _BackShininess;
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = unity_ObjectToWorld;
float4x4 modelMatrixInverse = unity_WorldToObject;
float3 normalDirection = normalize(
mul(float4(input.normal, 0.0), modelMatrixInverse).xyz);
float3 viewDirection = normalize(_WorldSpaceCameraPos
- mul(modelMatrix, input.vertex).xyz);
float3 lightDirection;
float attenuation;
if (0.0 == _WorldSpaceLightPos0.w) // directional light?
{
attenuation = 1.0; // no attenuation
lightDirection = normalize(_WorldSpaceLightPos0.xyz);
}
else // point or spot light
{
float3 vertexToLightSource = _WorldSpaceLightPos0.xyz
- mul(modelMatrix, input.vertex).xyz;
float distance = length(vertexToLightSource);
attenuation = 1.0 / distance; // linear attenuation
lightDirection = normalize(vertexToLightSource);
}
float3 ambientLighting =
UNITY_LIGHTMODEL_AMBIENT.rgb * _Color.rgb;
float3 diffuseReflection =
attenuation * _LightColor0.rgb * _Color.rgb
* max(0.0, dot(normalDirection, lightDirection));
float3 specularReflection;
if (dot(normalDirection, lightDirection) < 0.0)
// light source on the wrong side?
{
specularReflection = float3(0.0, 0.0, 0.0);
// no specular reflection
}
else // light source on the right side
{
specularReflection = attenuation * _LightColor0.rgb
* _SpecColor.rgb * pow(max(0.0, dot(
reflect(-lightDirection, normalDirection),
viewDirection)), _Shininess);
}
output.col = float4(ambientLighting + diffuseReflection
+ specularReflection, 1.0);
output.pos = UnityObjectToClipPos(input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
Pass {
Tags { "LightMode" = "ForwardAdd" }
// pass for additional light sources
Blend One One // additive blending
Cull Back // render only front faces
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
// User-specified properties
uniform float4 _Color;
uniform float4 _SpecColor;
uniform float _Shininess;
uniform float4 _BackColor;
uniform float4 _BackSpecColor;
uniform float _BackShininess;
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = unity_ObjectToWorld;
float4x4 modelMatrixInverse = unity_WorldToObject;
float3 normalDirection = normalize(
mul(float4(input.normal, 0.0), modelMatrixInverse).xyz);
float3 viewDirection = normalize(_WorldSpaceCameraPos
- mul(modelMatrix, input.vertex).xyz);
float3 lightDirection;
float attenuation;
if (0.0 == _WorldSpaceLightPos0.w) // directional light?
{
attenuation = 1.0; // no attenuation
lightDirection = normalize(_WorldSpaceLightPos0.xyz);
}
else // point or spot light
{
float3 vertexToLightSource = _WorldSpaceLightPos0.xyz
- mul(modelMatrix, input.vertex).xyz;
float distance = length(vertexToLightSource);
attenuation = 1.0 / distance; // linear attenuation
lightDirection = normalize(vertexToLightSource);
}
float3 diffuseReflection =
attenuation * _LightColor0.rgb * _Color.rgb
* max(0.0, dot(normalDirection, lightDirection));
float3 specularReflection;
if (dot(normalDirection, lightDirection) < 0.0)
// light source on the wrong side?
{
specularReflection = float3(0.0, 0.0, 0.0);
// no specular reflection
}
else // light source on the right side
{
specularReflection = attenuation * _LightColor0.rgb
* _SpecColor.rgb * pow(max(0.0, dot(
reflect(-lightDirection, normalDirection),
viewDirection)), _Shininess);
}
output.col = float4(diffuseReflection
+ specularReflection, 1.0);
// no ambient contribution in this pass
output.pos = UnityObjectToClipPos(input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
Pass {
Tags { "LightMode" = "ForwardBase" }
// pass for ambient light and first light source
Cull Front// render only back faces
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
// User-specified properties
uniform float4 _Color;
uniform float4 _SpecColor;
uniform float _Shininess;
uniform float4 _BackColor;
uniform float4 _BackSpecColor;
uniform float _BackShininess;
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = unity_ObjectToWorld;
float4x4 modelMatrixInverse = unity_WorldToObject;
float3 normalDirection = normalize(
mul(float4(-input.normal, 0.0), modelMatrixInverse).xyz);
float3 viewDirection = normalize(_WorldSpaceCameraPos
- mul(modelMatrix, input.vertex).xyz);
float3 lightDirection;
float attenuation;
if (0.0 == _WorldSpaceLightPos0.w) // directional light?
{
attenuation = 1.0; // no attenuation
lightDirection = normalize(_WorldSpaceLightPos0.xyz);
}
else // point or spot light
{
float3 vertexToLightSource = _WorldSpaceLightPos0.xyz
- mul(modelMatrix, input.vertex).xyz;
float distance = length(vertexToLightSource);
attenuation = 1.0 / distance; // linear attenuation
lightDirection = normalize(vertexToLightSource);
}
float3 ambientLighting =
UNITY_LIGHTMODEL_AMBIENT.rgb * _BackColor.rgb;
float3 diffuseReflection =
attenuation * _LightColor0.rgb * _BackColor.rgb
* max(0.0, dot(normalDirection, lightDirection));
float3 specularReflection;
if (dot(normalDirection, lightDirection) < 0.0)
// light source on the wrong side?
{
specularReflection = float3(0.0, 0.0, 0.0);
// no specular reflection
}
else // light source on the right side
{
specularReflection = attenuation * _LightColor0.rgb
* _BackSpecColor.rgb * pow(max(0.0, dot(
reflect(-lightDirection, normalDirection),
viewDirection)), _BackShininess);
}
output.col = float4(ambientLighting + diffuseReflection
+ specularReflection, 1.0);
output.pos = UnityObjectToClipPos(input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
Pass {
Tags { "LightMode" = "ForwardAdd" }
// pass for additional light sources
Blend One One // additive blending
Cull Front // render only back faces
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
// User-specified properties
uniform float4 _Color;
uniform float4 _SpecColor;
uniform float _Shininess;
uniform float4 _BackColor;
uniform float4 _BackSpecColor;
uniform float _BackShininess;
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = unity_ObjectToWorld;
float4x4 modelMatrixInverse = unity_WorldToObject;
float3 normalDirection = normalize(
mul(float4(-input.normal, 0.0), modelMatrixInverse).xyz);
float3 viewDirection = normalize(_WorldSpaceCameraPos
- mul(modelMatrix, input.vertex).xyz);
float3 lightDirection;
float attenuation;
if (0.0 == _WorldSpaceLightPos0.w) // directional light?
{
attenuation = 1.0; // no attenuation
lightDirection = normalize(_WorldSpaceLightPos0.xyz);
}
else // point or spot light
{
float3 vertexToLightSource = _WorldSpaceLightPos0.xyz
- mul(modelMatrix, input.vertex).xyz;
float distance = length(vertexToLightSource);
attenuation = 1.0 / distance; // linear attenuation
lightDirection = normalize(vertexToLightSource);
}
float3 diffuseReflection =
attenuation * _LightColor0.rgb * _BackColor.rgb
* max(0.0, dot(normalDirection, lightDirection));
float3 specularReflection;
if (dot(normalDirection, lightDirection) < 0.0)
// light source on the wrong side?
{
specularReflection = float3(0.0, 0.0, 0.0);
// no specular reflection
}
else // light source on the right side
{
specularReflection = attenuation * _LightColor0.rgb
* _BackSpecColor.rgb * pow(max(0.0, dot(
reflect(-lightDirection, normalDirection),
viewDirection)), _BackShininess);
}
output.col = float4(diffuseReflection
+ specularReflection, 1.0);
// no ambient contribution in this pass
output.pos = UnityObjectToClipPos(input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
}
Fallback "Specular"
}
此代码包含四个通道，其中第一对通道渲染正面，第二对通道使用反转的法线向量和背面材质属性渲染背面。每对中的第二个通道与第一个通道相同，除了混合方式为叠加，并且缺少环境色。
恭喜您完成了这个包含一个长着色器的简短教程。我们已经看到了
- 如何使用正面剔除和背面剔除来对网格的两侧应用不同的着色器。
- 如何更改背面三角形的 Phong 照明计算。
如果您想了解更多
- 关于单面表面的着色器版本，您应该阅读“镜面高光”部分.
- 关于 Cg 中的正面三角形和背面三角形，您应该阅读“截面”部分.
- 关于使用语义为
VFACE的片段输入参数来区分正面三角形和背面三角形，请参阅Unity 的着色器语义文档.
除非另有说明，否则本页上的所有示例源代码都归属公共领域。