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It's not a phase!
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- Optimize collecting light section edges
- Kinda an absurd amount of code, but I'm not sure how to parameterize
  by an axis without having capturing lambdas
- Around 3-4x faster
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@Jozufozu
Jozufozu committed Jul 13, 2024
1 parent d63e592 commit 1ccc4d4
Showing 1 changed file with 153 additions and 36 deletions.
189 changes: 153 additions & 36 deletions common/src/backend/java/dev/engine_room/flywheel/backend/engine/embed/LightStorage.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
import net.minecraft.core.SectionPos;
import net.minecraft.world.level.LevelAccessor;
import net.minecraft.world.level.LightLayer;
import net.minecraft.world.level.lighting.LayerLightEventListener;

/**
* TODO: AO data
Expand Down Expand Up @@ -110,10 +111,8 @@ public Plan<RenderContext> createFramePlan() {
}

// Now actually do the collection.
// TODO: Can this be done in parallel?
for (long section : sectionsToCollect) {
collectSection(section);
}
// TODO: Should this be done in parallel?
sectionsToCollect.forEach(this::collectSection);

requestedSections = null;
});
Expand Down Expand Up @@ -148,44 +147,137 @@ public void collectSection(long section) {
var blockLight = lightEngine.getLayerListener(LightLayer.BLOCK);
var skyLight = lightEngine.getLayerListener(LightLayer.SKY);

var blockPos = new BlockPos.MutableBlockPos();

int xMin = SectionPos.sectionToBlockCoord(SectionPos.x(section));
int yMin = SectionPos.sectionToBlockCoord(SectionPos.y(section));
int zMin = SectionPos.sectionToBlockCoord(SectionPos.z(section));

var sectionPos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(sectionPos);
var skyData = skyLight.getDataLayerData(sectionPos);

int index = indexForSection(section);

changed.set(index);

long ptr = arena.indexToPointer(index);

// Not sure of a way to iterate over the surface of a cube, so branch in the inner loop to take the fast path.
// Adding the fast path is about 8x faster than having only the slow path.
// There's still room for optimization, as the slow path takes about 3x the cpu time as the fast path despite
// being called an order of magnitude less.
for (int y = -1; y < 17; y++) {
for (int z = -1; z < 17; z++) {
for (int x = -1; x < 17; x++) {
if (x == -1 || y == -1 || z == -1 || x == 16 || y == 16 || z == 16) {
// Slow path, collect the surface of our section.
blockPos.set(xMin + x, yMin + y, zMin + z);
var block = blockLight.getLightValue(blockPos);
var sky = skyLight.getLightValue(blockPos);

write(ptr, x, y, z, block, sky);
} else {
// Fast path, read directly from the data layer for the main section.
// Would be nice to move the null check elsewhere.
var block = blockData == null ? 0 : blockData.get(x, y, z);
var sky = skyData == null ? 0 : skyData.get(x, y, z);

write(ptr, x, y, z, block, sky);
}
// Zero it out first. This is basically free and makes it easier to handle missing sections later.
MemoryUtil.memSet(ptr, 0, SECTION_SIZE_BYTES);

collectCenter(blockLight, skyLight, ptr, section);

for (SectionEdge i : SectionEdge.values()) {
collectYZPlane(blockLight, skyLight, ptr, SectionPos.offset(section, i.sectionOffset, 0, 0), i);
collectXZPlane(blockLight, skyLight, ptr, SectionPos.offset(section, 0, i.sectionOffset, 0), i);
collectXYPlane(blockLight, skyLight, ptr, SectionPos.offset(section, 0, 0, i.sectionOffset), i);

for (SectionEdge j : SectionEdge.values()) {
collectXStrip(blockLight, skyLight, ptr, SectionPos.offset(section, 0, i.sectionOffset, j.sectionOffset), i, j);
collectYStrip(blockLight, skyLight, ptr, SectionPos.offset(section, i.sectionOffset, 0, j.sectionOffset), i, j);
collectZStrip(blockLight, skyLight, ptr, SectionPos.offset(section, i.sectionOffset, j.sectionOffset, 0), i, j);
}
}

collectCorners(blockLight, skyLight, ptr, section);
}

private void collectXStrip(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section, SectionEdge y, SectionEdge z) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int x = 0; x < 16; x++) {
write(ptr, x, y.relative, z.relative, blockData.get(x, y.pos, z.pos), skyData.get(x, y.pos, z.pos));
}
}

private void collectYStrip(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section, SectionEdge x, SectionEdge z) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int y = 0; y < 16; y++) {
write(ptr, x.relative, y, z.relative, blockData.get(x.pos, y, z.pos), skyData.get(x.pos, y, z.pos));
}
}

private void collectZStrip(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section, SectionEdge x, SectionEdge y) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int z = 0; z < 16; z++) {
write(ptr, x.relative, y.relative, z, blockData.get(x.pos, y.pos, z), skyData.get(x.pos, y.pos, z));
}
}

private void collectYZPlane(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section, SectionEdge x) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int y = 0; y < 16; y++) {
for (int z = 0; z < 16; z++) {
write(ptr, x.relative, y, z, blockData.get(x.pos, y, z), skyData.get(x.pos, y, z));
}
}
}

private void collectXZPlane(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section, SectionEdge y) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int z = 0; z < 16; z++) {
for (int x = 0; x < 16; x++) {
write(ptr, x, y.relative, z, blockData.get(x, y.pos, z), skyData.get(x, y.pos, z));
}
}
}

private void collectXYPlane(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section, SectionEdge z) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int y = 0; y < 16; y++) {
for (int x = 0; x < 16; x++) {
write(ptr, x, y, z.relative, blockData.get(x, y, z.pos), skyData.get(x, y, z.pos));
}
}
}

private void collectCenter(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section) {
var pos = SectionPos.of(section);
var blockData = blockLight.getDataLayerData(pos);
var skyData = skyLight.getDataLayerData(pos);
if (blockData == null || skyData == null) {
return;
}
for (int y = 0; y < 16; y++) {
for (int z = 0; z < 16; z++) {
for (int x = 0; x < 16; x++) {
write(ptr, x, y, z, blockData.get(x, y, z), skyData.get(x, y, z));
}
}
}
}

private void collectCorners(LayerLightEventListener blockLight, LayerLightEventListener skyLight, long ptr, long section) {
var blockPos = new BlockPos.MutableBlockPos();
int xMin = SectionPos.sectionToBlockCoord(SectionPos.x(section));
int yMin = SectionPos.sectionToBlockCoord(SectionPos.y(section));
int zMin = SectionPos.sectionToBlockCoord(SectionPos.z(section));

for (SectionEdge x : SectionEdge.values()) {
for (SectionEdge y : SectionEdge.values()) {
for (SectionEdge z : SectionEdge.values()) {
blockPos.set(x.relative + xMin, y.relative + yMin, z.relative + zMin);
write(ptr, x.relative, y.relative, z.relative, blockLight.getLightValue(blockPos), skyLight.getLightValue(blockPos));
}
}
}
Expand Down Expand Up @@ -264,4 +356,29 @@ public IntArrayList createLut() {
// TODO: incremental lut updates
return LightLut.buildLut(section2ArenaIndex);
}

private enum SectionEdge {
LOW(15, -1, -1),
HIGH(0, 16, 1),
;

/**
* The position in the section to collect.
*/
private final int pos;
/**
* The position relative to the main section.
*/
private final int relative;
/**
* The offset to the neighboring section.
*/
private final int sectionOffset;

SectionEdge(int pos, int relative, int sectionOffset) {
this.pos = pos;
this.relative = relative;
this.sectionOffset = sectionOffset;
}
}
}

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