https://bzyzhang.github.io/2020/11/29/2020-11-29-%EF%BC%88%E4%B8%89%EF%BC%89%E8%A1%A8%E9%9D%A2%E5%87%B9%E5%87%B8%E6%8A%80%E6%9C%AF/
https://www.jianshu.com/p/fea6c9fc610f
[learn OpenGL] https://learnopengl-cn.github.io/05%20Advanced%20Lighting/05%20Parallax%20Mapping/
这里要感谢一下我的同事，这是他的博客 https://bzyzhang.github.io/
简介
- 视差贴图是表面凹凸技术的一种，原理是通过利用一张高度图去偏移UV伪装成真实高模，一般与法线贴图合用，因为一个项目里有用到，这里就研究了下，但是只是非常浅显的研究。
- 貌似就是为了让模型看起来，更突出一点，或者更凹一点
代码
Shader "Kaima/Bump/SimpleParallax"
{
Properties
{
[NoScaleOffset] _MainTex ("Texture", 2D) = "white" {
}
[NoScaleOffset] _NormalMap("Normal Map", 2D) = "bump" {
}
[NoScaleOffset] _DepthMap("Depth Map", 2D) = "white" {
}
_SpecularColor("Specular Color", Color) = (1,1,1,1)
_Gloss("Gloss", Range(32, 256)) = 64
_HeightScale("Height Scale", Range(0,1)) = 0.1
}
SubShader
{
Tags {
"RenderType"="Opaque" }
Pass
{
Tags {
"LightMode"="ForwardBase"}
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
#include "Lighting.cginc"
struct v2f
{
float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
float3 lightDir_tangent : TEXCOORD1;
float3 viewDir_tangent : TEXCOORD2;
};
sampler2D _MainTex;
sampler2D _NormalMap;
sampler2D _DepthMap;
fixed4 _SpecularColor;
float _Gloss;
float _HeightScale;
//最简单的实现，只是根据高度进行偏移
float2 ParallaxMapping(float2 uv, float3 viewDir_tangent)
{
float3 viewDir = normalize(viewDir_tangent);
float height = tex2D(_DepthMap, uv).r;
//因为viewDir是在切线空间的（xy与uv对齐），所以只用xy偏移就行了
float2 p = viewDir.xy / viewDir.z * (height * _HeightScale);
return uv - p;
}
v2f vert (appdata_tan v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = v.texcoord;
TANGENT_SPACE_ROTATION;
o.lightDir_tangent = normalize(mul(rotation, ObjSpaceLightDir(v.vertex)));
o.viewDir_tangent = normalize(mul(rotation, ObjSpaceViewDir(v.vertex)));
return o;
}
fixed4 frag (v2f i) : SV_Target
{
float3 lightDir = normalize(i.lightDir_tangent);
float3 viewDir = normalize(i.viewDir_tangent);
float2 uv = ParallaxMapping(i.uv, viewDir);
if(uv.x > 1.0 || uv.y > 1.0 || uv.x < 0.0 || uv.y < 0.0) //去掉边上的一些古怪的失真，在平面上工作得挺好的
discard;
float3 normal = normalize(UnpackNormal(tex2D(_NormalMap, uv)));
fixed4 albedo = tex2D(_MainTex, uv);
fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;
fixed3 diffuse = _LightColor0.rgb * albedo.rgb * saturate(dot(normal, i.lightDir_tangent));
float3 halfDir = normalize(lightDir + viewDir);
fixed3 specular = _LightColor0.rgb * _SpecularColor.rgb * pow(saturate(dot(halfDir, normal)), _Gloss);
fixed4 finalColor = fixed4(ambient + diffuse + specular, 1.0);
return finalColor;
}
ENDCG
}
}
}