From 00f17ddd622e6f4b128bf18f4b9fba5754f975df Mon Sep 17 00:00:00 2001
From: ssdfasd <2156608475@qq.com>
Date: Thu, 12 Mar 2026 00:42:28 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BC=98=E5=8C=96=E4=BD=93=E7=A7=AF=E6=B8=B2?=
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新增功能：
- 添加 phase_function()（返回 1.0）
- 使用 Unity 的累积公式：Sint = (S - S * exp(-sigmaE * step)) / sigmaE
- 添加 sigmaE 避免除零

与 Unity 版本的主要差异：
- 缺少 volumetric_shadow 体积阴影
- 缺少 ambient_light 环境光
- 缺少 acc_density 累积限制
- 缺少 Gamma 校正
---
 Res/Shader/volume.hlsl | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Res/Shader/volume.hlsl b/Res/Shader/volume.hlsl
index 9c156d50..e2f05418 100644
--- a/Res/Shader/volume.hlsl
+++ b/Res/Shader/volume.hlsl
@@ -85,6 +85,11 @@ bool get_hdda_hit(inout pnanovdb_readaccessor_t acc, inout float tmin, float3 or
     return hit;
 }
 
+float phase_function()
+{
+    return 1.0;
+}
+
 PSInput MainVS(VSInput input)
 {
     PSInput output;
@@ -167,9 +172,12 @@ float4 MainPS(PSInput input) : SV_TARGET
             continue;
         }
         
-        float3 S = density * float3(1, 1, 1);
-        color += transmittance * S * _StepSize;
-        transmittance *= exp(-density * _StepSize);
+        float sigmaS = density;
+        float sigmaE = max(0.000001, sigmaS);
+        float3 S = sigmaS * phase_function() * float3(1, 1, 1);
+        float3 Sint = (S - S * exp(-sigmaE * _StepSize)) / sigmaE;
+        color += transmittance * Sint;
+        transmittance *= exp(-sigmaE * _StepSize);
         
         tmin += _StepSize;
     }