make the sky loop around under the horizon

build.gradle.kts

@@ -85,7 +85,8 @@ subprojects {
 		runs.configureEach {
 			vmArg("-XX:+AllowEnhancedClassRedefinition")
 			vmArg("-XX:+IgnoreUnrecognizedVMOptions")
-			vmArg("-Dmixin.debug.export=true")
+			// Disabled by default: exports every mixin target to disk and can make startup hang for minutes.
+			// Enable manually when debugging mixins: -Dmixin.debug.export=true
 			vmArg("-Dmixin.env.remapRefMap=true")
 			vmArg("-Dmixin.env.refMapRemappingFile=${projectDir}/build/createSrgToMcp/output.srg")
 		}

common/src/main/java/io/github/slimeistdev/crystalline_sky/mixin/client/LevelRendererMixin.java

@@ -4,6 +4,7 @@ import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
 import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
 import com.mojang.blaze3d.pipeline.RenderTarget;
 import com.mojang.blaze3d.pipeline.TextureTarget;
+import com.mojang.blaze3d.systems.RenderSystem;
 import com.mojang.blaze3d.vertex.PoseStack;
 import io.github.slimeistdev.crystalline_sky.compat.Mods;
 import io.github.slimeistdev.crystalline_sky.compat.iris.IrisHelpers;
@@ -15,10 +16,12 @@ import net.minecraft.client.Camera;
 import net.minecraft.client.CloudStatus;
 import net.minecraft.client.DeltaTracker;
 import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.FogRenderer;
 import net.minecraft.client.renderer.GameRenderer;
 import net.minecraft.client.renderer.LevelRenderer;
 import net.minecraft.client.renderer.LightTexture;
 import net.minecraft.client.renderer.RenderType;
+import net.minecraft.util.Mth;
 import net.minecraft.world.phys.Vec3;
 import org.jetbrains.annotations.Nullable;
 import org.joml.Matrix4f;
@@ -48,6 +51,9 @@ public abstract class LevelRendererMixin implements LevelRenderer_Duck {
 	@Shadow
 	public abstract void renderClouds(PoseStack matrices, Matrix4f matrix4f, Matrix4f matrix4f2, float tickDelta, double cameraX, double cameraY, double cameraZ);
 
+	@Shadow
+	public abstract void renderSky(Matrix4f frustumMatrix, Matrix4f projectionMatrix, float partialTick, Camera camera, boolean isFoggy, Runnable skyFogSetup);
+
 	@Unique
 	@Nullable
 	private RenderTarget crystalline_sky$skyBuffer;
@@ -104,9 +110,15 @@ public abstract class LevelRendererMixin implements LevelRenderer_Duck {
 							  Matrix4f matrix4f, Matrix4f matrix4f2, CallbackInfo ci) {
 		var skyBuffer = crystalline_sky$getSkyFramebuffer();
 		skyBuffer.clear(Minecraft.ON_OSX);
-		var copiedFromIris = Mods.IRIS.runIfInstalled(() -> () -> IrisHelpers.copySkyToBuffer(skyBuffer));
-		if (!copiedFromIris.orElse(false))
-			((RenderTarget_Duck) skyBuffer).crystalline_sky$copyColorFrom(minecraft.getMainRenderTarget());
+
+		float partialTick = tickCounter.getGameTimeDeltaPartialTick(false);
+		if (crystalline_sky$isBelowHorizon(partialTick)) {
+			crystalline_sky$renderSkyBuffer(skyBuffer, tickCounter, camera, gameRenderer, matrix4f, matrix4f2);
+		} else {
+			var copiedFromIris = Mods.IRIS.runIfInstalled(() -> () -> IrisHelpers.copySkyToBuffer(skyBuffer));
+			if (!copiedFromIris.orElse(false))
+				((RenderTarget_Duck) skyBuffer).crystalline_sky$copyColorFrom(minecraft.getMainRenderTarget());
+		}
 
 		// render clouds
 		CloudStatus cloudRenderMode = this.minecraft.options.getCloudsType();
@@ -143,4 +155,60 @@ public abstract class LevelRendererMixin implements LevelRenderer_Duck {
 		renderSectionLayer(CrystallineRenderTypes.SKY, x, y, z, matrix4f, positionMatrix);
 		renderSectionLayer(CrystallineRenderTypes.SKYBOX, x, y, z, matrix4f, positionMatrix);
 	}
+
+	@Unique
+	private boolean crystalline_sky$isBelowHorizon(float partialTick) {
+		var level = minecraft.level;
+		var player = minecraft.player;
+		if (level == null || player == null) {
+			return false;
+		}
+
+		double eyeY = player.getEyePosition(partialTick).y;
+		double horizon = level.getLevelData().getHorizonHeight(level);
+		return eyeY < horizon;
+	}
+
+	@Unique
+	private void crystalline_sky$renderSkyBuffer(
+		RenderTarget skyBuffer,
+		DeltaTracker tickCounter,
+		Camera camera,
+		GameRenderer gameRenderer,
+		Matrix4f frustumMatrix,
+		Matrix4f projectionMatrix
+	) {
+		float partialTick = tickCounter.getGameTimeDeltaPartialTick(false);
+		Vec3 cameraPos = camera.getPosition();
+		float renderDistance = gameRenderer.getRenderDistance();
+		boolean isFoggy = minecraft.level.effects().isFoggyAt(Mth.floor(cameraPos.x), Mth.floor(cameraPos.y))
+			|| minecraft.gui.getBossOverlay().shouldCreateWorldFog();
+
+		skyBuffer.bindWrite(false);
+		SharedRenderVariables.pushSkipVoidSky();
+		try {
+			FogRenderer.setupColor(
+				camera,
+				partialTick,
+				minecraft.level,
+				minecraft.options.getEffectiveRenderDistance(),
+				gameRenderer.getDarkenWorldAmount(partialTick)
+			);
+			FogRenderer.levelFogColor();
+			RenderSystem.clear(16640, Minecraft.ON_OSX);
+			FogRenderer.setupFog(camera, FogRenderer.FogMode.FOG_SKY, renderDistance, isFoggy, partialTick);
+			RenderSystem.setShader(GameRenderer::getPositionShader);
+			this.renderSky(
+				frustumMatrix,
+				projectionMatrix,
+				partialTick,
+				camera,
+				isFoggy,
+				() -> FogRenderer.setupFog(camera, FogRenderer.FogMode.FOG_SKY, renderDistance, isFoggy, partialTick)
+			);
+		} finally {
+			SharedRenderVariables.popSkipVoidSky();
+			minecraft.getMainRenderTarget().bindWrite(false);
+		}
+	}
 }

common/src/main/java/io/github/slimeistdev/crystalline_sky/mixin/client/LevelRendererRenderSkyMixin.java

@@ -0,0 +1,32 @@
+package io.github.slimeistdev.crystalline_sky.mixin.client;
+
+import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
+import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
+import io.github.slimeistdev.crystalline_sky.util.SharedRenderVariables;
+import net.minecraft.client.multiplayer.ClientLevel;
+import net.minecraft.client.renderer.LevelRenderer;
+import net.minecraft.world.level.LevelHeightAccessor;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+
+@Mixin(value = LevelRenderer.class, remap = false)
+public class LevelRendererRenderSkyMixin {
+	@WrapOperation(
+		method = "renderSky",
+		at = @At(
+			value = "INVOKE",
+			target = "Lnet/minecraft/client/multiplayer/ClientLevel$ClientLevelData;getHorizonHeight(Lnet/minecraft/world/level/LevelHeightAccessor;)D"
+		)
+	)
+	private double crystalline_sky$skipVoidSkyWhenCapturing(
+		ClientLevel.ClientLevelData levelData,
+		LevelHeightAccessor level,
+		Operation<Double> original
+	) {
+		if (SharedRenderVariables.shouldSkipVoidSky()) {
+			return Double.NEGATIVE_INFINITY;
+		}
+
+		return original.call(levelData, level);
+	}
+}

common/src/main/java/io/github/slimeistdev/crystalline_sky/util/SharedRenderVariables.java

@@ -8,6 +8,7 @@ public class SharedRenderVariables {
 	// because chunk meshing is multithreaded :(
 	public static final ThreadLocal<MutableInt> shadeFullBright = ThreadLocal.withInitial(() -> new MutableInt(0));
 	private static int blockIrisShaderFramebufferBind = 0;
+	private static int skipVoidSky = 0;
 
 	public static boolean shouldShadeFullBright() {
 		return shadeFullBright.get().intValue() > 0;
@@ -32,4 +33,16 @@ public class SharedRenderVariables {
 	public static void popBlockIrisShaderFramebufferBind() {
 		blockIrisShaderFramebufferBind--;
 	}
+
+	public static boolean shouldSkipVoidSky() {
+		return skipVoidSky > 0;
+	}
+
+	public static void pushSkipVoidSky() {
+		skipVoidSky++;
+	}
+
+	public static void popSkipVoidSky() {
+		skipVoidSky--;
+	}
 }

common/src/main/resources/crystalline_sky-common.mixins.json

@@ -22,6 +22,7 @@
     "client.GameRendererMixin",
     "client.LevelRenderer_NoSodium_Mixin",
     "client.LevelRendererMixin",
+    "client.LevelRendererRenderSkyMixin",
     "client.ModelBlockRendererMixin",
     "client.RenderTargetMixin",
     "client.TextureAtlasAccessor",

gradle.properties

@@ -2,7 +2,10 @@
 org.gradle.jvmargs=-Xmx2G -XX:MaxMetaspaceSize=512m -Dfile.encoding=UTF-8
 # -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5006
 org.gradle.caching=true
-org.gradle.configureondemand=true
+# Disabled: with configure-on-demand, :fabric is not configured when running :neoforge:runClient,
+# but prepareArchitecturyTransformer queries all Loom projects and fails with
+# "Cannot get MappingsProvider before it has been setup".
+org.gradle.configureondemand=false
 # IntelliJ's run configs don't work with the configuration cache
 org.gradle.configuration-cache=false
 # Loom
@@ -26,7 +29,11 @@ modVersion=0.2.0
 branchName=1.21.1
 compatibleVersions=1.21.1
 
-# mod compat
+# mod compat (compileOnly)
 enable_sodium=true
 enable_iris=true
+# modLocalRuntime for Sodium/Iris hangs NeoForge dev startup for minutes (mixin stalls on RenderTarget).
+# For in-game Sodium/Iris testing, copy the jars into neoforge/run/mods/ instead.
+enable_sodium_runtime=false
+enable_iris_runtime=false
 enable_axiom=false

neoforge/build.gradle.kts

@@ -32,12 +32,12 @@ dependencies {
 
 	modCompileOnly(libs.ffapi.renderer) // only for sodium compat
 	modCompileOnly(libs.sodium.neoforge)
-	if (!inCI && "enable_sodium"().toBoolean()) { // this doesn't work, because of jar-in-jar. Sodium must be placed in the mods folder
+	if (!inCI && "enable_sodium_runtime"().toBoolean()) { // Sodium must be in run/mods for jar-in-jar; modLocalRuntime stalls dev startup
 		modLocalRuntime(libs.sodium.neoforge)
 	}
 
 	modCompileOnly(libs.iris.neoforge)
-	if (!inCI && "enable_iris"().toBoolean()) { // this doesn't work, because of jar-in-jar. Iris must be placed in the mods folder
+	if (!inCI && "enable_iris_runtime"().toBoolean()) { // Iris must be in run/mods for jar-in-jar; modLocalRuntime stalls dev startup
 		modLocalRuntime(libs.iris.neoforge)
 		/*modLocalRuntime("org.antlr:antlr4-runtime:4.13.1")
 		modLocalRuntime("io.github.douira:glsl-transformer:2.0.1")