Impostors: fix depth capture

1 files changed, 59 insertions, 8 deletions

diff --git a/impostor.cginc b/impostor.cginc
index e265438..f6c0d72 100644
--- a/impostor.cginc
+++ b/impostor.cginc
@@ -6,13 +6,16 @@
 
 SamplerState bilinear_clamp_s;
 Texture2D _ImpostorAtlas;
+Texture2D _ImpostorDepthAtlas;
 int _GridResolution;
+float _SphereRadius;
 float _Cutoff;
 float3 _ImpostorMainCameraPos;
 
 #ifndef IMPOSTOR_SHADOW_PASS
 float4 _Color;
 float _DebugMode;
+float _DebugDepth;
 #endif
 
 float2 HemiOctEncode(float3 N) {
@@ -45,6 +48,10 @@ float4 SampleAtlas(float2 uv, float2 cell) {
     return _ImpostorAtlas.Sample(bilinear_clamp_s, (cell + uv) / _GridResolution);
 }
 
+float SampleDepthAtlas(float2 uv, float2 cell) {
+    return _ImpostorDepthAtlas.Sample(bilinear_clamp_s, (cell + uv) / _GridResolution).r;
+}
+
 // ============================================================================
 // Vertex/Fragment
 // ============================================================================
@@ -62,10 +69,15 @@ struct v2f {
     V2F_SHADOW_CASTER;
 #else
     float4 pos : SV_POSITION;
-    UNITY_FOG_COORDS(3)
+    UNITY_FOG_COORDS(7)
 #endif
     float2 uv : TEXCOORD1;
     float2 cell : TEXCOORD2;
+    // For depth reconstruction
+    float3 worldPos : TEXCOORD3;
+    float3 viewWS : TEXCOORD4;
+    float3 center : TEXCOORD5;
+    float radius : TEXCOORD6;
     UNITY_VERTEX_OUTPUT_STEREO
 };
 
@@ -108,22 +120,61 @@ v2f vert(appdata v) {
     BillboardBasis(snapOS, right, up);
     o.uv = float2(1 - (dot(localOff, right) + 0.5), dot(localOff, up) + 0.5);
     o.cell = float2(cell);
+
+    // Pass data for depth reconstruction
+    float3 viewWS = normalize(camPos - center);
+    o.worldPos = worldPos;
+    o.viewWS = viewWS;
+    o.center = center;
+    o.radius = _SphereRadius * scale.x;
+
     return o;
 }
 
+#ifdef IMPOSTOR_SHADOW_PASS
+// Shadow pass - just alpha test, no depth output
 float4 frag(v2f i) : SV_Target {
     float4 col = SampleAtlas(i.uv, i.cell);
-#ifndef IMPOSTOR_SHADOW_PASS
-    if (_DebugMode > 0.5) return float4(1, 0, 0, 1);
-    col *= _Color;
-#endif
     clip(col.a - _Cutoff);
-#ifdef IMPOSTOR_SHADOW_PASS
     SHADOW_CASTER_FRAGMENT(i)
+}
 #else
+// Forward pass - with depth output
+struct FragOutput {
+    float4 color : SV_Target;
+    float depth : SV_Depth;
+};
+
+FragOutput frag(v2f i) {
+    FragOutput o;
+
+    float4 col = SampleAtlas(i.uv, i.cell);
+    float depth = SampleDepthAtlas(i.uv, i.cell);
+
+    // Compute depth-corrected world position
+    // depth=0 means front of sphere (toward camera), depth=1 means back (away from camera)
+    float3 depthWorldPos = i.worldPos - i.viewWS * (2.0 * depth - 1.0) * i.radius;
+
+    // Convert to clip space depth
+    float4 clipPos = mul(UNITY_MATRIX_VP, float4(depthWorldPos, 1.0));
+    o.depth = clipPos.z / clipPos.w;
+
+    if (_DebugMode > 0.5) {
+        o.color = float4(i.uv, 0, 1);
+        return o;
+    }
+    if (_DebugDepth > 0.5) {
+        o.color = float4(depth.xxx, 1);
+        return o;
+    }
+
+    col *= _Color;
+    clip(col.a - _Cutoff);
+
     UNITY_APPLY_FOG(i.fogCoord, col);
-    return col;
-#endif
+    o.color = col;
+    return o;
 }
+#endif
 
 #endif