Blending et Unity Terrain: comment se débarrasser des intersections et arrêter de se faire mal aux yeux

// Blending with depth buffer

#include "UnityCG.cginc"

float BlendStart;
float BlendEnd;
UNITY_DECLARE_DEPTH_TEXTURE(_CameraDepthTexture);

struct v2f
{
    // ...

    half4 projPos : TEXCOORD0;
};

v2f vert(appdata v)
{
    v2f o;
    UNITY_INITIALIZE_OUTPUT(v2f,o);

    // ...

    o.projPos = ComputeScreenPos(o.pos);
    COMPUTE_EYEDEPTH(o.projPos.z);

    // ...

    return o;
}

fixed4 frag(v2f i) : COLOR
{     
    fixed4 result = 0;
      
    // ... 

    float depth = SAMPLE_DEPTH_TEXTURE_PROJ(_CameraDepthTexture, UNITY_PROJ_COORD(i.projPos));
    float sceneZ = LinearEyeDepth(depth);
    float partZ = i.projPos.z;
    float fade = saturate( sceneZ - partZ );
    result.a = smoothstep( BlendStart, BlendEnd, fade );

    // ... 
       
    return result; 
}

// Blending with terrain heightmap

#include "UnityCG.cginc"

float BlendStart;
float BlendEnd;

sampler2D_float TerrainHeightmap; 
float4 HeightmapScale;
float4 TerrainSize;
float4 TerrainPos;        

struct v2f
{
   // ...

   float3 worldPos : TEXCOORD0;
   float2 heightMapUV : TEXCOORD1;

   // ...
};


v2f vert(appdata v)
{
    v2f o;
    UNITY_INITIALIZE_OUTPUT(v2f,o);
   
    // ...
    
    o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
    o.heightMapUV = TerrainUV(o.worldPos);

    // ...

    return o;
}

fixed4 frag(v2f i) : COLOR
{
    fixed4 result = 0;

    // ... 

    half height = TerrainHeight(i.heightMapUV);
    half deltaHeight = i.worldPos.y - height;
    result.a = smoothstep( BlendStart, BlendEnd, deltaHeight );

    // ... 
       
    return result; 
}

// Blending with reconstructed terrain fragments

#include "UnityCG.cginc"

float BlendStart;
float BlendEnd;

sampler2D_float TerrainHeightmapTexture;
sampler2D_float TerrainNormalTexture;
sampler2D TerrainAlphaMap;

float4 HeightmapScale;
float4 TerrainSize;
float4 TerrainPos;
Float4 TerrainLightmap_ST;

UNITY_DECLARE_TEX2D(TerrainSplatMap0);
UNITY_DECLARE_TEX2D_NOSAMPLER(TerrainNormalMap0);
half4 TerrainSplatMap0_ST;

UNITY_DECLARE_TEX2D(TerrainSplatMap1);
UNITY_DECLARE_TEX2D_NOSAMPLER(TerrainNormalMap1);
half4 TerrainSplatMap1_ST;

UNITY_DECLARE_TEX2D(TerrainSplatMap2);
UNITY_DECLARE_TEX2D_NOSAMPLER(TerrainNormalMap2);
half4 TerrainSplatMap2_ST;

UNITY_DECLARE_TEX2D(TerrainSplatMap3);
UNITY_DECLARE_TEX2D_NOSAMPLER(TerrainNormalMap3);
half4 TerrainSplatMap3_ST;

struct v2f
{
   // ...

   float3 worldPos : TEXCOORD0;
   float2 heightMapUV : TEXCOORD1;
#if defined(LIGHTMAP_ON)
   float2 modelLightMapUV : TEXCOORD2;
   float2 terrainLightMapUV : TEXCOORD3;
#endif

   // ...
};


v2f vert(appdata v)
{
    v2f o;
    UNITY_INITIALIZE_OUTPUT(v2f,o);
   
    // ...
    
    o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
    o.heightMapUV = TerrainUV(o.worldPos);

#if defined(LIGHTMAP_ON)
    o.modelLightMapUV = v.texcoord1.xy * unity_LightmapST.xy + unity_LightmapST.zw;
    o.terrainLightMapUV = o.heightMapUV * TerrainLightmap_ST.xy + TerrainLightmap_ST.zw;
#endif

    // ...

    return o;
}
half3 TerrainNormal(float2 terrainUV)
{
    return tex2Dlod( TerrainNormalTexture, float4(terrainUV,0,0) ).xyz * 2.0 - 1.0;
}

half4 TerrainSplatMap(float2 uv0, float2 uv1, float2 uv2, float2 uv3, half4 control)
{
    half4 splat0 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainSplatMap0, TerrainSplatMap0, uv0);
    half4 splat1 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainSplatMap1, TerrainSplatMap1, uv1);
    half4 splat2 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainSplatMap2, TerrainSplatMap2, uv2);
    half4 splat3 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainSplatMap3, TerrainSplatMap3, uv3);         
    half4 result = splat0 * control.r + 
                   splat1 * control.g + 
                   splat2 * control.b + 
                   splat3 * control.a;
    return result;
}

half3 TerrainNormalMap(float2 uv0, float2 uv1, float2 uv2, float2 uv3, half4 control)
{
    half4 n0 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainNormalMap0, TerrainSplatMap0, uv0);
    half4 n1 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainNormalMap1, TerrainSplatMap1, uv1);
    half4 n2 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainNormalMap2, TerrainSplatMap2, uv2);
    half4 n3 = UNITY_SAMPLE_TEX2D_SAMPLER(TerrainNormalMap3, TerrainSplatMap3, uv3);
    half3 result = UnpackNormalWithScale(n0, 1.0) * control.r +
                   UnpackNormalWithScale(n1, 1.0) * control.g +
                   UnpackNormalWithScale(n2, 1.0) * control.b +
                   UnpackNormalWithScale(n3, 1.0) * control.a;
    result.z += 1e-5;
    return result;
}

half3 TerrainLightmap(float2 uv, half3 normal)
{
#if defined(LIGHTMAP_ON)
#if defined(DIRLIGHTMAP_COMBINED)
    half4 lm = UNITY_SAMPLE_TEX2D(unity_Lightmap, uv);
    half4 lmd = UNITY_SAMPLE_TEX2D_SAMPLER(unity_LightmapInd, unity_Lightmap, uv);
    half3 result = DecodeLightmapRGBM(lm, unity_Lightmap_HDR);
    result = DecodeDirectionalLightmap(result, lmd, normal);
#else
    half4 lm = UNITY_SAMPLE_TEX2D(unity_Lightmap, uv);
    half3 result = DecodeLightmapRGBM(lm, unity_Lightmap_HDR);
#endif                
#else
    half3 result = UNITY_LIGHTMODEL_AMBIENT.rgb;
#endif
    return result;
}

fixed4 frag(v2f i) : COLOR
{
    fixed4 result = 0;

    // ...

    // compute model color and put it to the result

    // ... 

    // reconstruction of terrain fragment

    float2 splatUV0 = TRANSFORM_TEX(i.heightMapUV, TerrainSplatMap0);
    float2 splatUV1 = TRANSFORM_TEX(i.heightMapUV, TerrainSplatMap1);
    float2 splatUV2 = TRANSFORM_TEX(i.heightMapUV, TerrainSplatMap2);
    float2 splatUV3 = TRANSFORM_TEX(i.heightMapUV, TerrainSplatMap3);

    half4 control = tex2D(_TerrainAlphaMap, i.heightMapUV);
    half4 terrainColor = TerrainSplatMap(splatUV0, splatUV1, splatUV2, splatUV3, control);

    half3 terrainSurfaceNormal = TerrainNormal(i.heightMapUV);
    half3 terrainSurfaceTangent = cross(terrainSurfaceNormal, float3(0,0,1));
    half3 terrainSurfaceBitangent = cross(terrainSurfaceTangent, terrainSurfaceNormal);

    half3 terrainNormal = TerrainNormalMap(splatUV0, splatUV1, splatUV2, splatUV3, control);
    terrainNormal = terrainNormal.x * terrainSurfaceTangent + 
                    terrainNormal.y * terrainSurfaceBitangent + 
                    terrainNormal.z * terrainSurfaceNormal;
    
    half3 terrainLightmapColor = TerrainLightmap(i.heightMapUV, terrainNormal);
    terrainColor *= terrainLightmapColor;

    // blend model color & terrain color

    half height = TerrainHeight(i.heightMapUV);
    half deltaHeight = i.worldPos.y - height;
    half blendingWeight = smoothstep(BlendStart, BlendEnd, deltaHeight);

    result.rgb = lerp(result.rgb, terrainColor, blendingFactor);
       
    return result; 
}

// Per-vertex snapping with terrain heightmap

#include "UnityCG.cginc"

sampler2D_float TerrainHeightmapTexture;

float4 HeightmapScale;
float4 TerrainSize;
float4 TerrainPos;

struct v2f
{

   // ...

   float3 worldPos : TEXCOORD0;
   float2 heightMapUV : TEXCOORD1;

   // ...

};

v2f vert(appdata v)
{
    v2f o;
    UNITY_INITIALIZE_OUTPUT(v2f,o);
   
    // ...
    
    o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
    o.heightMapUV = TerrainUV(o.worldPos);
    float snappingWeight = v.color.r;                
    half height = TerrainHeight( o.heightMapUV );                
    o.worldPos.y = lerp( o.worldPos.y, height, snappingWeight );
    o.pos = UnityWorldToClipPos( half4( o.worldPos, 1 ) );

    // ...

    return o;
}