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Cache loaded tile heights to reduce flickering #89

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merged 1 commit into from
Oct 13, 2024
Merged

Cache loaded tile heights to reduce flickering #89

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7 changes: 6 additions & 1 deletion engine/src/Core/HashMap.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -211,7 +211,7 @@ class HashMap
return *this;
}

HashMap& operator=(HashMap&& other)
HashMap& operator=(HashMap&& other) noexcept
{
if (data != nullptr)
{
Expand Down Expand Up @@ -398,6 +398,11 @@ class HashMap
}
}

void Remove(const Iterator& iterator)
{
Remove(iterator.current);
}

void Remove(KeyValuePair* pair)
{
if (pair != &zeroPair)
Expand Down
97 changes: 56 additions & 41 deletions engine/src/Graphics/TerrainQuadTree.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -236,7 +236,8 @@ TerrainQuadTree::TerrainQuadTree() :
parentsToCheck(nullptr),
neighborsToCheck(nullptr),
edgeDependencies(nullptr),
tileIdToIndexMap(nullptr)
tileIdToIndexMap(nullptr),
nodeHeightCache(nullptr)
{
}

Expand All @@ -248,7 +249,8 @@ TerrainQuadTree::TerrainQuadTree(Allocator* allocator, render::Device* renderDev
parentsToCheck(allocator),
neighborsToCheck(allocator),
edgeDependencies(allocator),
tileIdToIndexMap(allocator)
tileIdToIndexMap(allocator),
nodeHeightCache(allocator)
{
}

Expand All @@ -261,6 +263,7 @@ TerrainQuadTree::TerrainQuadTree(TerrainQuadTree&& other) noexcept :
neighborsToCheck(std::move(other.neighborsToCheck)),
edgeDependencies(std::move(other.edgeDependencies)),
tileIdToIndexMap(std::move(other.tileIdToIndexMap)),
nodeHeightCache(std::move(other.nodeHeightCache)),
tileData(std::move(other.tileData)),
treeLevels(other.treeLevels),
maxNodeLevel(other.maxNodeLevel),
Expand All @@ -281,6 +284,7 @@ TerrainQuadTree& TerrainQuadTree::operator=(TerrainQuadTree&& other) noexcept
neighborsToCheck = std::move(other.neighborsToCheck);
edgeDependencies = std::move(other.edgeDependencies);
tileIdToIndexMap = std::move(other.tileIdToIndexMap);
nodeHeightCache = std::move(other.nodeHeightCache);
tileData = std::move(other.tileData);
treeLevels = other.treeLevels;
maxNodeLevel = other.maxNodeLevel;
Expand Down Expand Up @@ -314,6 +318,7 @@ void TerrainQuadTree::SetHeightmap(const uint16_t* pixels, uint32_t resolution)
{
tileData.count = 0;
tileIdToIndexMap.Clear();
nodeHeightCache.Clear();

treeLevels = GetLevelsFromHeightmapResolution(resolution);
heightmapPixels = pixels;
Expand All @@ -332,6 +337,9 @@ void TerrainQuadTree::UpdateTilesToRender(
drawTiles.Clear();
maxNodeLevel = 0;

// Used for cache eviction
currentTime = Time::GetRunningTime();

// Calculates optimal set of tiles to render and updates quad tree <nodes>
UpdateTilesToRenderParams params{ frustum, cameraPos, renderDebug };
int rootNodeIndex = BuildQuadTree(QuadTreeNodeId{}, params);
Expand All @@ -358,14 +366,39 @@ ArrayView<const TerrainTileDrawInfo> TerrainQuadTree::GetTilesToRender() const

int TerrainQuadTree::BuildQuadTree(const QuadTreeNodeId& id, const UpdateTilesToRenderParams& params)
{
AABB tileBounds = FindApproximateTileBounds(id);
float width = tileBounds.extents.x * 2.0f;
auto cacheKv = nodeHeightCache.Lookup(id);
QuadTreeNodeId searchId = id;
while (cacheKv == nullptr && searchId.level != 0)
{
searchId = GetParentId(searchId);
cacheKv = nodeHeightCache.Lookup(searchId);
}

float minHeight = terrainBottom;
float maxHeight = terrainBottom + terrainHeight;
if (cacheKv != nullptr)
{
HeightCacheEntry& entry = cacheKv->second;
minHeight = entry.min / static_cast<float>(UINT16_MAX) * terrainHeight + terrainBottom;
maxHeight = entry.max / static_cast<float>(UINT16_MAX) * terrainHeight + terrainBottom;
entry.lastAccessTime = currentTime;
}

float tileScale = GetTileScale(id.level);
float tileWidth = terrainWidth * tileScale;
float halfSize = terrainWidth * 0.5f;
Vec3f tileMin(id.x * tileWidth - halfSize, minHeight, id.y * tileWidth - halfSize);
Vec3f tileSize(tileWidth, maxHeight - minHeight, tileWidth);

AABB tileBounds;
tileBounds.extents = tileSize * 0.5f;
tileBounds.center = tileMin + tileBounds.extents;

if (Intersect::FrustumAabb(params.frustum, tileBounds) == false)
return -1;

bool lastLevel = id.level + 1 == treeLevels;
bool tileIsSmallEnough = lastLevel || (width < (tileBounds.center - params.cameraPos).Magnitude() * lodSizeFactor);
bool tileIsSmallEnough = lastLevel || (tileWidth < (tileBounds.center - params.cameraPos).Magnitude() * lodSizeFactor);

int nodeIndex = static_cast<int>(nodes.GetCount());
assert(nodeIndex <= UINT16_MAX);
Expand Down Expand Up @@ -596,7 +629,6 @@ void TerrainQuadTree::QuadTreeToTiles(uint16_t nodeIndex)

void TerrainQuadTree::LoadTiles()
{
const double currentTime = Time::GetRunningTime();
const double oldTileThresholdTime = currentTime - 10.0;

// Unload tiles that haven't been used for a while
Expand Down Expand Up @@ -707,6 +739,11 @@ void TerrainQuadTree::LoadTiles()
tile.minHeight = heightData.min;
tile.maxHeight = heightData.max;

auto cacheKv = nodeHeightCache.Insert(drawTile.id);
cacheKv->second.min = heightData.min;
cacheKv->second.max = heightData.max;
cacheKv->second.lastAccessTime = currentTime;

renderDevice->SetTextureSubImage2D(tileData.textureIds[tileIdx], 0, 0, 0,
texResolution, texResolution, RenderTextureBaseFormat::R,
RenderTextureDataType::UnsignedShort, heightData.data);
Expand All @@ -716,6 +753,19 @@ void TerrainQuadTree::LoadTiles()
tileData.count += 1;
}
}

// Unload old height cache entries

const double oldCacheThresholdTime = currentTime - 300.0;

for (auto itr = nodeHeightCache.begin(), end = nodeHeightCache.end(); itr != end; ++itr)
{
if (itr->second.lastAccessTime < oldCacheThresholdTime)
{
nodeHeightCache.Remove(itr);
break; // Only remove one entry per update as removal invalidates iterators
}
}
}

void TerrainQuadTree::LoadTileData(const QuadTreeNodeId& id, TerrainTileHeightData& heightDataOut)
Expand Down Expand Up @@ -756,41 +806,6 @@ void TerrainQuadTree::LoadTileData(const QuadTreeNodeId& id, TerrainTileHeightDa
heightDataOut.max = max;
}

AABB TerrainQuadTree::FindApproximateTileBounds(const QuadTreeNodeId& id) const
{
auto pair = tileIdToIndexMap.Lookup(id);
QuadTreeNodeId searchId = id;
while (pair == nullptr)
{
if (searchId.level == 0)
break;

searchId = GetParentId(searchId);
tileIdToIndexMap.Lookup(searchId);
}

float minHeight = terrainBottom;
float maxHeight = terrainBottom + terrainHeight;
if (pair != nullptr)
{
TerrainTile& tile = tileData.tiles[pair->second];
minHeight = tile.minHeight / static_cast<float>(UINT16_MAX) * terrainHeight + terrainBottom;
maxHeight = tile.maxHeight / static_cast<float>(UINT16_MAX) * terrainHeight + terrainBottom;
}

float tileScale = GetTileScale(id.level);
float tileWidth = terrainWidth * tileScale;
float halfSize = terrainWidth * 0.5f;
Vec3f tileMin(id.x * tileWidth - halfSize, minHeight, id.y * tileWidth - halfSize);
Vec3f tileSize(tileWidth, maxHeight - minHeight, tileWidth);

AABB bounds;
bounds.extents = tileSize * 0.5f;
bounds.center = tileMin + bounds.extents;

return bounds;
}

render::TextureId TerrainQuadTree::GetTileHeightTexture(const QuadTreeNodeId& id)
{
auto pair = tileIdToIndexMap.Lookup(id);
Expand Down
35 changes: 21 additions & 14 deletions engine/src/Graphics/TerrainQuadTree.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -78,18 +78,6 @@ enum class TerrainEdgeType : uint8_t
LeftTopSparse
};

struct TerrainQuadTreeNode
{
QuadTreeNodeId id;
uint16_t children[4] = { 0, 0, 0, 0 };
TerrainEdgeType edgeType = TerrainEdgeType::Regular;

uint16_t HasChildren() const
{
return children[0] != 0 || children[1] != 0 || children[2] != 0 || children[3] != 0;
}
};

struct TerrainTileDrawInfo
{
QuadTreeNodeId id;
Expand Down Expand Up @@ -134,6 +122,18 @@ class TerrainQuadTree
static float GetTileScale(uint8_t level);

private:
struct TerrainQuadTreeNode
{
QuadTreeNodeId id;
uint16_t children[4] = { 0, 0, 0, 0 };
TerrainEdgeType edgeType = TerrainEdgeType::Regular;

uint16_t HasChildren() const
{
return children[0] != 0 || children[1] != 0 || children[2] != 0 || children[3] != 0;
}
};

struct UpdateTilesToRenderParams
{
const FrustumPlanes& frustum;
Expand All @@ -149,6 +149,13 @@ class TerrainQuadTree
void AddDependent(uint16_t dependent);
};

struct HeightCacheEntry
{
uint16_t min;
uint16_t max;
double lastAccessTime;
};

// Returns inserted node index (points to nodes array), or -1 if no insertion
int BuildQuadTree(const QuadTreeNodeId& id, const UpdateTilesToRenderParams& params);
void RestrictQuadTree();
Expand All @@ -158,8 +165,6 @@ class TerrainQuadTree
void LoadTiles();
void LoadTileData(const QuadTreeNodeId& id, TerrainTileHeightData& heightDataOut);

AABB FindApproximateTileBounds(const QuadTreeNodeId& id) const;

Allocator* allocator;
render::Device* renderDevice;

Expand All @@ -169,6 +174,7 @@ class TerrainQuadTree
SortedArray<QuadTreeNodeId> neighborsToCheck;
HashMap<QuadTreeNodeId, EdgeTypeDependents> edgeDependencies; // Key = dependee node, Value = dependent nodes
HashMap<QuadTreeNodeId, uint32_t> tileIdToIndexMap; // Index into tileData
HashMap<QuadTreeNodeId, HeightCacheEntry> nodeHeightCache;

struct TileData
{
Expand Down Expand Up @@ -197,6 +203,7 @@ class TerrainQuadTree
float terrainBottom = 0.0f;
float terrainHeight = 0.0f;
float lodSizeFactor = 0.5f;
double currentTime = -1.0;
};

}