Exploration of the sand shader game Journey

Part 4: Mirror Image

Rim lighting

float4 LightingJourney (SurfaceOutput s, fixed3 viewDir, UnityGI gi)
{
    // Lighting properties
    float3 L = gi.light.dir;
    float3 N = s.Normal;

    // Lighting calculation
    float3 diffuseColor	= DiffuseColor (N, L);
    float3 rimColor     = RimLighting  (N, V);

    // Combining
    float3 color = diffuseColor + rimColor;

    // Final color
    return float4(color * s.Albedo, 1);
}

Fresnel Reflections

float _TerrainRimPower;
float _TerrainRimStrength;
float3 _TerrainRimColor;

float3 RimLighting(float3 N, float3 V)
{
    float rim = 1.0 - saturate(dot(N, V));
    rim = saturate(pow(rim, _TerrainRimPower) * _TerrainRimStrength);
    rim = max(rim, 0); // Never negative
    return rim * _TerrainRimColor;
}

Ocean specular

float4 LightingJourney (SurfaceOutput s, fixed3 viewDir, UnityGI gi)
{
    // Lighting properties
    float3 L = gi.light.dir;
    float3 N = s.Normal;
    float3 V = viewDir;

    // Lighting calculation
    float3 diffuseColor	= DiffuseColor  (N, L);
    float3 rimColor     = RimLighting   (N, V);
    float3 oceanColor   = OceanSpecular (N, L, V);

    // Combining
    float3 specularColor = saturate(max(rimColor, oceanColor));
    float3 color = diffuseColor + specularColor;

    // Final color
    return float4(color * s.Albedo, 1);
}

Why is H between V and L?

, , $$$H$— $$$V$$$$L$.

, . $$$V$$$$L$$$$L$$$$V$$$$V$$$$L$.

, , $$$V+L$$$$L+V$, . , :

, , . , ( $$$V+L$) . , ( ).

, $$$V+L$— $$$V$$$$L$, $$$1$. , $$$1$, ( ).

float _OceanSpecularPower;
float _OceanSpecularStrength;
float3 _OceanSpecularColor;

float3 OceanSpecular (float3 N, float3 L, float3 V)
{
    // Blinn-Phong
    float3 H = normalize(V + L); // Half direction
    float NdotH = max(0, dot(N, H));
    float specular = pow(NdotH, _OceanSpecularPower) * _OceanSpecularStrength;
    return specular * _OceanSpecularColor;
}

Part 5: brilliant reflection

Theory of Microfaces

Implementation

sampler2D_float _GlitterTex;
float _GlitterThreshold;
float3 _GlitterColor;

float3 GlitterSpecular (float2 uv, float3 N, float3 L, float3 V)
{
    // Random glitter direction
    float3 G = normalize(tex2D(_GlitterTex, uv).rgb * 2 - 1); // [0,1]->[-1,+1]

    // Light that reflects on the glitter and hits the eye
    float3 R = reflect(L, G);
    float RdotV = max(0, dot(R, V));
	
    // Only the strong ones (= small RdotV)
    if (RdotV > _GlitterThreshold)
        return 0;
	
    return (1 - RdotV) * _GlitterColor;
}

#pragma surface surf Journey fullforwardshadows

float4 LightingJourney (SurfaceOutput s, fixed3 viewDir, UnityGI gi)
{
    float3 diffuseColor = DiffuseColor    ();
    float3 rimColor     = RimLighting     ();
    float3 oceanColor   = OceanSpecular   ();
    float3 glitterColor = GlitterSpecular ();

    float3 specularColor = saturate(max(rimColor, oceanColor));
    float3 color = diffuseColor + specularColor + glitterColor;
	
    return float4(color * s.Albedo, 1);
}

Part 6: waves

Normal Maps

Waves in the sand

Realization of the waves

Normal Maps

• Geometry Normal : the orientation of each face of the 3D model, which is stored directly at the vertices;
• Sand normal : calculated using noise texture;
• Wave Normal : The new effect discussed in this part.

  Shader "Example/Diffuse Bump" {
    Properties {
      _MainTex ("Texture", 2D) = "white" {}
      _BumpMap ("Bumpmap", 2D) = "bump" {}
    }
    SubShader {
      Tags { "RenderType" = "Opaque" }
      CGPROGRAM
      #pragma surface surf Lambert
      struct Input {
        float2 uv_MainTex;
        float2 uv_BumpMap;
      };
      sampler2D _MainTex;
      sampler2D _BumpMap;
      void surf (Input IN, inout SurfaceOutput o) {
        o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb;
        o.Normal = UnpackNormal (tex2D (_BumpMap, IN.uv_BumpMap));
      }
      ENDCG
    } 
    Fallback "Diffuse"
  }

Steepness of the dunes

inline fixed3 UnpackNormal(fixed4 packednormal)
{
#if defined(SHADER_API_GLES)  defined(SHADER_API_MOBILE)
    return packednormal.xyz * 2 - 1;
#else
    fixed3 normal;
    normal.xy = packednormal.wy * 2 - 1;
    normal.z = sqrt(1 - normal.x*normal.x - normal.y * normal.y);
    return normal;
#endif
}

struct Input
{
    ...

    float3 worldNormal;
    INTERNAL_DATA
};

INTERNAL_DATA — , o.Normal.

, WorldNormalVector (IN, o.Normal).

What is INTERNAL_DATA?

INTERNAL_DATA Unity.

, , WorldNormalVector. , , . ( ).

, 3D- 3×3. , , (tangent to world matrix), Unity TtoW.

INTERNAL_DATA TtoW Input. , «Show generated code» :

, INTERNAL_DATA — , TtoW:

#define INTERNAL_DATA
    half3 internalSurfaceTtoW0;
    half3 internalSurfaceTtoW1;
    half3 internalSurfaceTtoW2;

half3x3, half3.

WorldNormalVector, , ( ) TtoW:

#define WorldNormalVector(data,normal)
    fixed3
    (
        dot(data.internalSurfaceTtoW0, normal),
        dot(data.internalSurfaceTtoW1, normal),
        dot(data.internalSurfaceTtoW2, normal)
    )

mul, TtoW , .

, :

$$

$$\begin{equation*} \begin{bmatrix} ToW_{1,1} & ToW_{1,2} & ToW_{1,3} \\ ToW_{2,1} & ToW_{2,2} & ToW_{2,3} \\ ToW_{3,1} & ToW_{3,2} & ToW_{3,3} \end{bmatrix} \cdot \begin{bmatrix} N1\\ N2\\ N3 \end{bmatrix}= \begin{bmatrix} \begin{bmatrix} ToW_{1,1} \\ ToW_{1,2} \\ ToW_{1,3} \end{bmatrix}\cdot\begin{bmatrix} N1\\ N2\\ N3 \end{bmatrix} \\ \begin{bmatrix} ToW_{2,1} \\ ToW_{2,2} \\ ToW_{2,3} \end{bmatrix}\cdot\begin{bmatrix} N1\\ N2\\ N3 \end{bmatrix} \\ \begin{bmatrix} ToW_{3,1} \\ ToW_{3,2} \\ ToW_{3,3} \end{bmatrix}\cdot\begin{bmatrix} N1\\ N2\\ N3 \end{bmatrix} \end{bmatrix} \end{equation*}$$

LearnOpenGL.

Implementation

// Calculates normal in world space
float3 N_WORLD = WorldNormalVector(IN, o.Normal);
float3 UP_WORLD = float3(0, 1, 0);

// Calculates "steepness"
// => 0: steep (90 degrees surface)
//  => 1: shallow (flat surface)
float steepness = saturate(dot(N_WORLD, UP_WORLD));

float2 uv = W.xz;

// [0,1]->[-1,+1]
float3 shallow = UnpackNormal(tex2D(_ShallowTex, TRANSFORM_TEX(uv, _ShallowTex)));
float3 steep   = UnpackNormal(tex2D(_SteepTex,   TRANSFORM_TEX(uv, _SteepTex  )));

// Steepness normal
float3 S = normalerp(steep, shallow, steepness);

Wave mixing

// Steepness to blending
steepness = pow(steepness, _SteepnessSharpnessPower);

Direction of the dunes

Conclusion

Acknowledgments

Unity Package