From b685fe06617e9e6ea620bbdb5d294d2098c5129e Mon Sep 17 00:00:00 2001
From: doodlum <15017472+doodlum@users.noreply.github.com>
Date: Tue, 21 Apr 2026 17:01:34 +0100
Subject: [PATCH] Revert "perf(terrain shadows): half res and 4x faster updates
 (#2163)"

This reverts commit 7661ba7e0c1ac840233b2c46b83b507e6d498578.
---
 .../TerrainShadows/ShadowUpdate.cs.hlsl       | 22 ++++++-------------
 src/Features/TerrainShadows.cpp               | 21 ++++--------------
 2 files changed, 11 insertions(+), 32 deletions(-)

diff --git a/features/Terrain Shadows/Shaders/TerrainShadows/ShadowUpdate.cs.hlsl b/features/Terrain Shadows/Shaders/TerrainShadows/ShadowUpdate.cs.hlsl
index f4f162cf40..c434a1e09d 100644
--- a/features/Terrain Shadows/Shaders/TerrainShadows/ShadowUpdate.cs.hlsl	
+++ b/features/Terrain Shadows/Shaders/TerrainShadows/ShadowUpdate.cs.hlsl	
@@ -63,15 +63,8 @@ float2 GetInterpolatedHeightRW(float2 pxCoord, bool isVertical)
 groupshared float2 g_shadowHeight[NTHREADS];
 
 [numthreads(NTHREADS, 1, 1)] void main(const uint gtid : SV_GroupThreadID, const uint gid : SV_GroupID) {
-	// Two independent coordinate spaces are used here: the heightmap sampling
-	// space (TexHeight) and the shadow-pixel space (RWTexShadowHeights). The
-	// CPU path may resize the height texture independently of the shadow
-	// resolution, so sampling and resizing can be done separately for each
-	// space. LightPxDir and PxSize are expressed in shadow-pixel units.
-	uint2 heightDims;
-	TexHeight.GetDimensions(heightDims.x, heightDims.y);
-	uint2 shadowDims;
-	RWTexShadowHeights.GetDimensions(shadowDims.x, shadowDims.y);
+	uint2 dims;
+	TexHeight.GetDimensions(dims.x, dims.y);
 
 	bool isVertical = abs(LightPxDir.y) > abs(LightPxDir.x);
 	float2 lightUVDir = LightPxDir * PxSize;
@@ -84,19 +77,18 @@ groupshared float2 g_shadowHeight[NTHREADS];
 	bool isValid = isVertical ? isUVinRange.y : isUVinRange.x;
 
 	float2 threadUV = rawThreadUV - floor(rawThreadUV);  // wraparound
-	float2 heightPxCoord = threadUV * heightDims;
-	float2 shadowPxCoord = threadUV * shadowDims;
+	float2 threadPxCoord = threadUV * dims;
 
 	float2 pastHeights = 0.0;
 	if (isValid) {
-		pastHeights = RWTexShadowHeights[uint2(shadowPxCoord)];
+		pastHeights = RWTexShadowHeights[uint2(threadPxCoord)];
 
 		// bifilter
-		float2 heights = GetInterpolatedHeight(heightPxCoord, isVertical).xx;
+		float2 heights = GetInterpolatedHeight(threadPxCoord, isVertical).xx;
 
 		// fetch last dispatch
 		if (gtid == 0 && all(floor(rawThreadUV - lightUVDir) == floor(rawThreadUV))) {
-			float2 sampleHeights = GetInterpolatedHeightRW(shadowPxCoord - LightPxDir, isVertical) + LightDeltaZ;
+			float2 sampleHeights = GetInterpolatedHeightRW(threadPxCoord - LightPxDir, isVertical) + LightDeltaZ;
 			heights = heights.x > sampleHeights.x ? heights : sampleHeights;
 		}
 
@@ -121,6 +113,6 @@ groupshared float2 g_shadowHeight[NTHREADS];
 
 	// save
 	if (isValid) {
-		RWTexShadowHeights[uint2(shadowPxCoord)] = lerp(pastHeights, g_shadowHeight[gtid], 0.5f);
+		RWTexShadowHeights[uint2(threadPxCoord)] = lerp(pastHeights, g_shadowHeight[gtid], 0.5f);
 	}
 }
\ No newline at end of file
diff --git a/src/Features/TerrainShadows.cpp b/src/Features/TerrainShadows.cpp
index 413158f60f..df9efb40d9 100644
--- a/src/Features/TerrainShadows.cpp
+++ b/src/Features/TerrainShadows.cpp
@@ -224,17 +224,7 @@ void TerrainShadows::LoadHeightmap()
 			std::filesystem::path path{ target_heightmap.dir };
 			path /= target_heightmap.filename;
 
-			DirectX::ScratchImage rawImage;
-			DX::ThrowIfFailed(LoadFromDDSFile(path.c_str(), DirectX::DDS_FLAGS_NONE, nullptr, rawImage));
-
-			// Downscale heightmap to 1/2 resolution per axis to match the
-			// shadow texture and speed up full shadow updates by ~4x.
-			auto& rawMeta = rawImage.GetMetadata();
-			size_t newWidth = std::max<size_t>(1, rawMeta.width / 2);
-			size_t newHeight = std::max<size_t>(1, rawMeta.height / 2);
-			DX::ThrowIfFailed(DirectX::Resize(
-				rawImage.GetImages(), rawImage.GetImageCount(), rawMeta,
-				newWidth, newHeight, DirectX::TEX_FILTER_LINEAR, image));
+			DX::ThrowIfFailed(LoadFromDDSFile(path.c_str(), DirectX::DDS_FLAGS_NONE, nullptr, image));
 		} catch (const DX::com_exception& e) {
 			logger::error("{}", e.what());
 			return;
@@ -343,11 +333,8 @@ void TerrainShadows::UpdateShadow()
 	TracyD3D11Zone(globals::state->tracyCtx, "Terrain Occlusion - Update Shadows");
 
 	/* ---- UPDATE CB ---- */
-	// Shadow texture is 1/2 heightmap resolution per axis; ray stepping,
-	// dispatch and PxSize all operate in shadow-pixel space, while the
-	// shader still samples the full-res heightmap via UV.
-	uint width = texShadowHeight->desc.Width;
-	uint height = texShadowHeight->desc.Height;
+	uint width = texHeightMap->desc.Width;
+	uint height = texHeightMap->desc.Height;
 
 	// only update direction at the start of each cycle
 	static uint edgePxCoord;
@@ -393,7 +380,7 @@ void TerrainShadows::UpdateShadow()
 	}
 
 	shadowUpdateCBData.StartPxCoord = edgePxCoord + signDir * shadowUpdateIdx * updateLength;
-	shadowUpdateCBData.PxSize = { 1.f / width, 1.f / height };
+	shadowUpdateCBData.PxSize = { 1.f / texHeightMap->desc.Width, 1.f / texHeightMap->desc.Height };
 
 	shadowUpdateCBData.PosRange = { cachedHeightmap->pos0.z, cachedHeightmap->pos1.z };
 	shadowUpdateCBData.ZRange = cachedHeightmap->zRange;