[VFX] Fix soft particles

com.unity.render-pipelines.high-definition/Runtime/VFXGraph/Shaders/VFXCommon.hlsl

@@ -144,11 +144,6 @@ float VFXSampleDepth(float4 posSS)
     return LoadCameraDepth(posSS.xy);
 }
 
-float VFXLinearEyeDepth(float depth)
-{
-    return LinearEyeDepth(depth,_ZBufferParams);
-}
-
 void VFXApplyShadowBias(inout float4 posCS, inout float3 posWS, float3 normalWS)
 {
 }

com.unity.render-pipelines.universal/CHANGELOG.md

@@ -142,6 +142,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed ShaderGraph materials to select render queue in the same way as handwritten shader materials by default, but allows for a user override for custom behavior. [case 1335795]
 - Fixed sceneview debug mode rendering (case 1211436).
 - URP Global Settings can now be unassigned in the Graphics tab (case 1343570).
+- VFX: Fixed soft particles when HDR or Opaque texture isn't enabled
+- VFX: Fixed OpenGL soft particles fallback when depth texture isn't available
 
 ### Changed
 - Change Asset/Create/Shader/Universal Render Pipeline/Lit Shader Graph to Asset/Create/Shader Graph/URP/Lit Shader Graph

com.unity.render-pipelines.universal/Runtime/VFXGraph/Shaders/VFXCommon.hlsl

@@ -116,12 +116,13 @@ float3 GetWorldStereoOffset()
 
 float VFXSampleDepth(float4 posSS)
 {
-    return LoadSceneDepth(uint2(posSS.xy));
-}
+    float2 screenUV = GetNormalizedScreenSpaceUV(posSS.xy);
 
-float VFXLinearEyeDepth(float depth)
-{
-    return LinearEyeDepth(depth, _ZBufferParams);
+    // In URP, the depth texture is optional and could be 4x4 white texture, Load isn't appropriate in that case.
+    //float depth = LoadSceneDepth(screenUV * _ScreenParams.xy);
+    float depth = SampleSceneDepth(screenUV);
+
+    return depth;
 }
 
 void VFXApplyShadowBias(inout float4 posCS, inout float3 posWS, float3 normalWS)

com.unity.visualeffectgraph/CHANGELOG.md

@@ -66,6 +66,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fix incorrect buffer type for strips
 - Enabled an optimization for motion vectors, storing projected positions for vertices instead of the transform matrix
 - VFX Graph operators keep the same width when expanded or collpased so that the button does not change position
+- Fix Soft Particle depth computation when using an orthographic camera [Case 1309961](https://issuetracker.unity3d.com/product/unity/issues/guid/1309961)
 
 ## [11.0.0] - 2020-10-21
 ### Added

com.unity.visualeffectgraph/Shaders/Common/VFXCommonCompute.hlsl

@@ -54,7 +54,12 @@ float3 VFXGetViewWorldPosition()
     return (float3)0.0f;
 }
 
-float VFXLinearEyeDepth(float4 posSS)
+float VFXLinearEyeDepth(float depth)
+{
+    return 0.0f;
+}
+
+float VFXLinearEyeDepthOrthographic(float depth)
 {
     return 0.0f;
 }

com.unity.visualeffectgraph/Shaders/VFXCommonOutput.hlsl

@@ -96,12 +96,36 @@ float4 VFXGetParticleColor(VFX_VARYING_PS_INPUTS i)
     return color;
 }
 
+float VFXLinearEyeDepth(float depth)
+{
+    return LinearEyeDepth(depth, _ZBufferParams);
+}
+
+float VFXLinearEyeDepthOrthographic(float depth)
+{
+#if UNITY_REVERSED_Z
+    return float(_ProjectionParams.z - (_ProjectionParams.z - _ProjectionParams.y) * depth);
+#else
+    return float(_ProjectionParams.y + (_ProjectionParams.z - _ProjectionParams.y) * depth);
+#endif
+}
+
 float VFXGetSoftParticleFade(VFX_VARYING_PS_INPUTS i)
 {
     float fade = 1.0f;
     #if USE_SOFT_PARTICLE && defined(VFX_VARYING_INVSOFTPARTICLEFADEDISTANCE)
-    float sceneZ = VFXLinearEyeDepth(VFXSampleDepth(i.VFX_VARYING_POSCS));
-    fade = saturate(i.VFX_VARYING_INVSOFTPARTICLEFADEDISTANCE * (sceneZ - i.VFX_VARYING_POSCS.w));
+    float sceneZ, selfZ;
+    if(IsPerspectiveProjection())
+    {
+        sceneZ = VFXLinearEyeDepth(VFXSampleDepth(i.VFX_VARYING_POSCS));
+        selfZ = i.VFX_VARYING_POSCS.w;
+    }
+    else
+    {
+        sceneZ = VFXLinearEyeDepthOrthographic(VFXSampleDepth(i.VFX_VARYING_POSCS));
+        selfZ = VFXLinearEyeDepthOrthographic(i.VFX_VARYING_POSCS.z);
+    }
+    fade = saturate(i.VFX_VARYING_INVSOFTPARTICLEFADEDISTANCE * (sceneZ - selfZ));
     fade = fade * fade * (3.0 - (2.0 * fade)); // Smoothsteping the fade
     #endif
     return fade;