February 19, 2023

Unity Shader 学习 Texture Repetition

Unity Shader 学习 Texture Repetition

目的

为了解决三向和双向的重复问题

参考资料

Coding

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Shader "Unlit/Biplanar_Texture_Repetition"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _NoramlTex ("Noraml Texture", 2D) = "white" {}
        _shapek ("shapek", Range(0,20)) = 1
        _BlendRatio ("BlendRatio",Float ) = 1
        _TriplanarBlendSharpness("Blend Sharpness", float)=1
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float4 normal   : NORMAL;
                float4 tangent  : TANGENT;
            };

            struct v2f
            {
                float4 pos    : SV_POSITION;
                float2 uv : TEXCOORD0;
                float4 posWS    : TEXCOORD1;
                float3 nDirWS   : TEXCOORD2;
                float3 tDirWS   : TEXCOORD3;  // 世界空间切线方向
                float3 bDirWS   : TEXCOORD4; 
            };
            Texture2D _MainTex;
            SamplerState sampler_MainTex;
            float4 _MainTex_ST;
            Texture2D _NoramlTex;
            //sampler2D _MainTex;float4 _MainTex_ST;
            //sampler2D _NoramlTex;
            float _shapek;
            float _BlendRatio;
            float _TriplanarBlendSharpness;

            v2f vert (appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos( v.vertex );  
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.posWS = mul(unity_ObjectToWorld, v.vertex);
                o.nDirWS = UnityObjectToWorldNormal(v.normal);  // 法线方向 OS>WS
                o.tDirWS = normalize(mul(unity_ObjectToWorld, float4(v.tangent.xyz, 0.0)).xyz); // 切线方向 OS>WS
                o.bDirWS = normalize(cross(o.nDirWS, o.tDirWS) * v.tangent.w); 
                return o;
            }
            //哈希算法
            float4 hash4(float2 p)
            {
            float t1 = 1.0 + dot(p, float2(37.0, 17.0));
            float t2 = 2.0 + dot(p, float2(11.0, 47.0));
            float t3 = 3.0 + dot(p, float2(41.0, 29.0));
            float t4 = 4.0 + dot(p, float2(23.0, 31.0));
            return frac(sin(float4(t1, t2, t3, t4)) * 103.0);
            }
            // 清除纹理本体
            float4 texNoTileTech(Texture2D baseTex, SamplerState baseTexSampler, float2 uv, float2 blendRatio)
            {
            // 获取整数部分，即哪个tile
            float2 iuv = floor(uv);
            // 获取小数部分，确认采样点在单个tile中的位置
            float2 fuv = frac(uv);

            // 产生四次不同的变换
            float4 ofa = hash4(iuv + float2(0.0, 0.0));
            float4 ofb = hash4(iuv + float2(1.0, 0.0));
            float4 ofc = hash4(iuv + float2(0.0, 1.0));
            float4 ofd = hash4(iuv + float2(1.0, 1.0));

            // 计算ddx,ddy避免UV跳跃
            float2 dx = ddx(uv);
            float2 dy = ddy(uv);

            // 镜像处理
            ofa.zw = sign(ofa.zw - 0.5);
            ofb.zw = sign(ofb.zw - 0.5);
            ofc.zw = sign(ofc.zw - 0.5);
            ofd.zw = sign(ofd.zw - 0.5);

            float2 uva = uv * ofa.zw + ofa.xy, dxa = dx * ofa.zw, dya = dy * ofa.zw;
            float2 uvb = uv * ofb.zw + ofb.xy, dxb = dx * ofb.zw, dyb = dy * ofb.zw;
            float2 uvc = uv * ofc.zw + ofc.xy, dxc = dx * ofc.zw, dyc = dy * ofc.zw;
            float2 uvd = uv * ofd.zw + ofd.xy, dxd = dx * ofd.zw, dyd = dy * ofd.zw;

            // 采样和混合
            float2 b = smoothstep(blendRatio, 1.0 - blendRatio, fuv);

            float4 sampler1 = baseTex.SampleGrad(baseTexSampler, uva, dxa, dya);
            float4 sampler2 = baseTex.SampleGrad(baseTexSampler, uvb, dxb, dyb);
            float4 sampler3 = baseTex.SampleGrad(baseTexSampler, uvc, dxc, dyc);
            float4 sampler4 = baseTex.SampleGrad(baseTexSampler, uvd, dxd, dyd);

            return lerp(lerp(sampler1, sampler2, b.x), lerp(sampler3, sampler4, b.x), b.y);
            //return float4(uva,0,0);
            }
            fixed4 frag (v2f i) : SV_Target
            {
                //数据构建
                float3 p = i.posWS;
	            float3 dpdx = ddx(p);
                float3 dpdy = ddy(p);
                float3 n = abs(i.nDirWS);
                uint3 ma =	(n.x>n.y&&n.x>n.z)	? uint3(0,1,2):
                            (n.y>n.z)			? uint3(1,2,0):
                                                  uint3(2,0,1);

                uint3 mi =	(n.x<n.y&&n.x<n.z)	? uint3(0,1,2):
                            (n.y<n.z)			? uint3(1,2,0):
                                                  uint3(2,0,1);
                uint3 me =	uint3(3,3,3)-mi-ma;

                float2 w = float2(n[ma.x],n[me.x]);
                w = saturate((w-0.5)/(1-0.5));
                float k  = _shapek/8.0;
                w = pow(w,_TriplanarBlendSharpness);
                w=pow(w,float2(k,k));
                // sample the texture
                float4 x = _MainTex.SampleGrad(sampler_MainTex,float2(p[ma.y],p[ma.z]),float2(dpdx[ma.y],dpdx[ma.z]),float2(dpdy[ma.y],dpdy[ma.z]));
	            float4 y = _MainTex.SampleGrad(sampler_MainTex,float2(p[me.y],p[me.z]),float2(dpdx[me.y],dpdx[me.z]),float2(dpdy[me.y],dpdy[me.z]));
                //fixed4 col = tex2D(_MainTex, i.uv);
                //_MainTex.Sample(sampler_MainTex, i.uv);
                // apply fog

                fixed4 cx = texNoTileTech(_MainTex,sampler_MainTex,float2(p[ma.y],p[ma.z]),_BlendRatio);
                fixed4 cy = texNoTileTech(_MainTex,sampler_MainTex,float2(p[me.y],p[me.z]),_BlendRatio);
                float4 col = (cx*w.x+cy*w.y)/(w.x+w.y);
                //float4 col = (x*w.x+y*w.y)/(w.x+w.y);

                //ramp world y
                //NORMAL
                
                fixed4 Nx = texNoTileTech(_NoramlTex,sampler_MainTex,float2(p[ma.y],p[ma.z]),_BlendRatio);
                fixed4 Ny = texNoTileTech(_NoramlTex,sampler_MainTex,float2(p[me.y],p[me.z]),_BlendRatio);
                //float4 Nx = tex2Dgrad(_NoramlTex,float2(p[ma.y],p[ma.z]),float2(dpdx[ma.y],dpdx[ma.z]),float2(dpdy[ma.y],dpdy[ma.z]));
	            //float4 Ny = tex2Dgrad(_NoramlTex,float2(p[me.y],p[me.z]),float2(dpdx[me.y],dpdx[me.z]),float2(dpdy[me.y],dpdy[me.z]));
                float3 n1 = UnpackNormal(Nx);
                float3 n2 = UnpackNormal(Ny);

                float3 nW;
                float3 n1W = float3(n1.y+i.nDirWS[ma.z],n1.x+i.nDirWS[ma.y],abs(n1.z)*i.nDirWS[ma.x]);
                float3 n2W = float3(n2.y+i.nDirWS[me.z],n2.x+i.nDirWS[me.y],abs(n2.z)*i.nDirWS[me.x]);

                n1W = float3(n1W[ma.z],n1W[ma.y],n1W[ma.x]);
                n2W = float3(n2W[me.z],n2W[me.y],n2W[me.x]);
                //nW = normalize(n1*w.x+n2*w.y);
                nW = normalize(n1W*w.x+n2W*w.y);
                float3 normalT = mul(nW,float3x3(i.tDirWS,i.bDirWS,i.nDirWS));
                half3 lDirWS = _WorldSpaceLightPos0.xyz;

                half ndotl = dot(nW, lDirWS);


                return fixed4(col.rgb*ndotl,1);

            }
            ENDCG
        }
    }
}

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本文作者 Master Gong Sheng, 许可由 CC BY-NC 4.0.