From a79ea9414b824886b0ce1e1db2377648d0b38aa9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ricardo=20Lu=C3=ADs=20Vaz=20Silva?= <ricolvs123@gmail.com>
Date: Sun, 6 Oct 2024 20:27:21 -0300
Subject: [PATCH] inverse square lights for sprites

had to add a minimum distance to make sure smaller lights don't completely blow out actors nearby
---
 .../hwrenderer/scene/hw_spritelight.cpp        | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/rendering/hwrenderer/scene/hw_spritelight.cpp b/src/rendering/hwrenderer/scene/hw_spritelight.cpp
index 031262daf..866024653 100644
--- a/src/rendering/hwrenderer/scene/hw_spritelight.cpp
+++ b/src/rendering/hwrenderer/scene/hw_spritelight.cpp
@@ -112,6 +112,15 @@ public:
 //
 //==========================================================================
 
+
+float inverseSquareAttenuation(FVector3 lightpos, float dist, float radius)
+{
+	float strength = 1500.0;
+	float a = dist / radius;
+	float b = clamp(1.0 - a * a * a * a, 0.0, 1.0);
+	return (b * b) / (dist * dist + 1.0) * strength;
+}
+
 void HWDrawInfo::GetDynSpriteLight(AActor *self, float x, float y, float z, FLightNode *node, int portalgroup, float *out)
 {
 	FDynamicLight *light;
@@ -167,7 +176,14 @@ void HWDrawInfo::GetDynSpriteLight(AActor *self, float x, float y, float z, FLig
 
 				if (staticLight.TraceLightVisbility(node, L, dist))
 				{
-					frac = 1.0f - (dist / radius);
+					if(level.info->lightattenuationmode == ELightAttenuationMode::INVERSE_SQUARE)
+					{
+						frac = (inverseSquareAttenuation(L, std::max(dist, sqrt(radius) * 2), radius));
+					}
+					else
+					{
+						frac = 1.0f - (dist / radius);
+					}
 
 					if (light->IsSpot())
 					{