1 files changed, 195 insertions, 0 deletions
diff --git a/Shaders/cloud/cloud_lighting.cginc b/Shaders/cloud/cloud_lighting.cginc
new file mode 100644
index 0000000..771d21d
--- /dev/null
+++ b/Shaders/cloud/cloud_lighting.cginc
@@ -0,0 +1,195 @@
+#ifndef CLOUD_LIGHTING
+#define CLOUD_LIGHTING
+
+#include "AutoLight.cginc"
+#include "UnityPBSLighting.cginc"
+#include "iq_sdf.cginc"
+#include "math.cginc"
+#include "Motion.cginc"
+#include "pbr.cginc"
+#include "pema99.cginc"
+
+#define MY_COORD_SCALE 100
+#define MY_COORD_SCALE_INV 1.0 / MY_COORD_SCALE
+#define OBJ_SPACE_TO_MINE \
+  float4x4( \
+      MY_COORD_SCALE, 0, 0, 0, \
+      0, MY_COORD_SCALE, 0, 0, \
+      0, 0, MY_COORD_SCALE, 0, \
+      0, 0, 0, MY_COORD_SCALE \
+      )
+#define WORLD_SPACE_TO_MINE \
+  mul(unity_WorldToObject, OBJ_SPACE_TO_MINE)
+#define MY_SPACE_TO_OBJ \
+  float4x4( \
+      MY_COORD_SCALE_INV, 0, 0, 0, \
+      0, MY_COORD_SCALE_INV, 0, 0, \
+      0, 0, MY_COORD_SCALE_INV, 0, \
+      0, 0, 0, MY_COORD_SCALE_INV \
+      )
+#define MY_SPACE_TO_WORLD \
+  mul(MY_SPACE_TO_OBJ, unity_ObjectToWorld)
+
+#define MINIMUM_HIT_DISTANCE .00002 * MY_COORD_SCALE
+#define MAXIMUM_TRACE_DISTANCE 20 * MY_COORD_SCALE
+
+float _Ball_Height;
+float _Ball_Scale;
+float _Cloud_Y_Off;
+float _Cloud_Opacity;
+float _Cloud_W;
+float _Cloud_Scale;
+float _Sphere_Scale;
+float _Global_Scale;
+float4 _Orientation;
+float3 _Offset;
+
+// Return the density of the mist at position `p`.
+float mist_map(float3 p)
+{
+  float scale = MY_COORD_SCALE * _Global_Scale;
+  float dist_fade = max(length(p / scale) - .8, 0) * 12;
+  dist_fade = 1 / (1 + dist_fade);
+
+  p.x += _Time[0] * scale * .1;
+  float noise = clamp(fbm(p * _Cloud_Scale / scale, /*n_octaves=*/5, _Cloud_W), 0, 1);
+  noise *= noise;
+
+  // On [0,1]
+  float y_fade = p.y / scale + .5;
+  y_fade -= _Cloud_Y_Off;
+  y_fade = max(0, y_fade);
+  y_fade = 1 - y_fade;
+  noise *= y_fade;
+
+  return clamp(noise * dist_fade, 0, 1);
+}
+
+float3 mist_march(float3 ro, float3 rd, out float density)
+{
+  float3 current_position;
+#define CLOUD_MARCH_ITER 7
+  float scale = MY_COORD_SCALE * _Global_Scale;
+  float step_sz = (float(scale) / CLOUD_MARCH_ITER);
+  float total_distance = (CLOUD_MARCH_ITER - 1) * step_sz;
+
+  // Dither starting point to avoid color banding
+  total_distance += step_sz * rand3(ro.xyz);
+
+  float mist_v = 0;
+  for (int i = CLOUD_MARCH_ITER - 1; (i >= 0); --i)
+  {
+    current_position = ro + total_distance * rd;
+
+    float4 cur_world_pos = mul(MY_SPACE_TO_WORLD, float4(current_position, MY_COORD_SCALE));
+    float d0 = getWorldSpaceDepth(cur_world_pos);
+    float d1 = getDepthBufferAt(cur_world_pos);
+    //bool use_result = (d0 < d1);
+    bool use_result = true;
+    {
+      float3 axis = _Orientation.xyz;
+      float theta = _Orientation.w;
+
+      Quaternion q = Quaternion(axis * cos(theta/2), sin(theta/2));
+      current_position = qrot(current_position, q);
+    }
+
+    float cur_v = mist_map(current_position) * _Cloud_Opacity;
+    float new_mist = cur_v + mist_v * (1 - cur_v);
+    mist_v = lerp(mist_v, new_mist, use_result);
+
+    total_distance -= step_sz;
+  }
+
+  density = mist_v;
+
+  return current_position;
+}
+
+float4 mist_ray_march(float3 ro, float3 rd, inout v2f v2f_i)
+{
+  float density;
+  float3 final_pos = mist_march(ro, rd, density);
+
+  // Mist scatters light. The denser it is, the more it scatters it.
+  float r0 = rand3(v2f_i.worldPos + float3(_Time[0], 0, 0));
+  float r1 = rand3(v2f_i.worldPos + float3(0, _Time[0], 0));
+  float r2 = rand3(v2f_i.worldPos + float3(0, 0, _Time[0]));
+  v2f_i.normal = normalize(v2f_i.normal + density * normalize(float3(r0, r1, r2)));
+
+  density = pow(density, 2) * 2;
+  density = smoothstep_quintic(density);
+  return float4(1, 1, 1, density);
+}
+
+float4 ray_march(inout v2f v2f_i)
+{
+  float4 ray_march_color;
+  {
+    float3 camera_position = mul(WORLD_SPACE_TO_MINE, float4(_WorldSpaceCameraPos, 1.0)).xyz;
+    float3 ro = camera_position;
+    float3 mesh_position = mul(WORLD_SPACE_TO_MINE, v2f_i.worldPos).xyz;
+    float3 rd = normalize(mesh_position - ro);
+    ro = mesh_position;
+
+    float4 mist_color = mist_ray_march(ro, rd, v2f_i);
+    ray_march_color = clamp(mist_color, 0, 1);
+  }
+
+  return ray_march_color;
+}
+
+void getVertexLightColor(inout v2f i)
+{
+  #if defined(VERTEXLIGHT_ON)
+  float3 light_pos = float3(unity_4LightPosX0.x, unity_4LightPosY0.x,
+      unity_4LightPosZ0.x);
+  float3 light_vec = light_pos - i.worldPos;
+  float3 light_dir = normalize(light_vec);
+  float ndotl = DotClamped(i.normal, light_dir);
+  // Light fills an expanding sphere with surface area 4 * pi * r^2.
+  // By conservation of energy, this means that at distance r, light intensity
+  // is proportional to 1/(r^2).
+  float attenuation = 1 / (1 + dot(light_vec, light_vec) * unity_4LightAtten0.x);
+  i.vertexLightColor = unity_LightColor[0].rgb * ndotl * attenuation;
+
+  i.vertexLightColor = Shade4PointLights(
+    unity_4LightPosX0, unity_4LightPosY0, unity_4LightPosZ0,
+    unity_LightColor[0].rgb,
+    unity_LightColor[1].rgb,
+    unity_LightColor[2].rgb,
+    unity_LightColor[3].rgb,
+    unity_4LightAtten0, i.worldPos, i.normal
+  );
+  #endif
+}
+
+v2f vert(appdata v)
+{
+  v2f o;
+  o.position = UnityObjectToClipPos(v.position);
+  o.worldPos = mul(unity_ObjectToWorld, v.position);
+  o.normal = UnityObjectToWorldNormal(v.normal);
+
+  o.uv = v.uv;
+  getVertexLightColor(o);
+
+  return o;
+}
+
+fixed4 frag(v2f i) : SV_Target
+{
+  float4 mist_unlit = ray_march(i);
+
+  float4 mist_lit = light(
+      i,
+      mist_unlit,
+      /*metallic=*/0,
+      /*smoothness=*/0.7);
+  float emission_str = 1.0;
+  float4 mist_color = mist_lit + float4((mist_unlit * emission_str).xyz, 0);
+
+  return mist_color;
+}
+
+#endif  // CLOUD_LIGHTING