Add a hook for blocks to suppress a neighboring fluid overlay

patches/net/minecraft/client/renderer/block/LiquidBlockRenderer.java.patch

@@ -1,15 +1,36 @@
 --- a/net/minecraft/client/renderer/block/LiquidBlockRenderer.java
 +++ b/net/minecraft/client/renderer/block/LiquidBlockRenderer.java
-@@ -37,6 +_,7 @@
+@@ -37,12 +_,17 @@
          this.waterIcons[0] = Minecraft.getInstance().getModelManager().getBlockModelShaper().getBlockModel(Blocks.WATER.defaultBlockState()).getParticleIcon();
          this.waterIcons[1] = ModelBakery.WATER_FLOW.sprite();
          this.waterOverlay = ModelBakery.WATER_OVERLAY.sprite();
 +        net.neoforged.neoforge.client.textures.FluidSpriteCache.reload();
      }
 
      private static boolean isNeighborSameFluid(FluidState p_203186_, FluidState p_203187_) {
-@@ -70,8 +_,9 @@
+         return p_203187_.getType().isSame(p_203186_.getType());
+     }
+
++    private static boolean isNeighborStateHidingOverlay(FluidState selfState, BlockState otherState, Direction neighborFace) {
++        return otherState.shouldHideAdjacentFluidFace(neighborFace, selfState);
++    }
++
+     private static boolean isFaceOccludedByState(Direction p_110980_, float p_110981_, BlockState p_110983_) {
+         VoxelShape voxelshape = p_110983_.getFaceOcclusionShape(p_110980_.getOpposite());
+         if (voxelshape == Shapes.empty()) {
+@@ -64,14 +_,20 @@
+         return isFaceOccludedByState(p_110963_.getOpposite(), 1.0F, p_110962_);
+     }
 
++    /** @deprecated Neo: use overload that accepts BlockState */
+     public static boolean shouldRenderFace(FluidState p_203169_, BlockState p_203170_, Direction p_203171_, FluidState p_203172_) {
+         return !isFaceOccludedBySelf(p_203170_, p_203171_) && !isNeighborSameFluid(p_203169_, p_203172_);
+     }
+
++    public static boolean shouldRenderFace(FluidState fluidState, BlockState selfState, Direction direction, BlockState otherState) {
++        return !isFaceOccludedBySelf(selfState, direction) && !isNeighborStateHidingOverlay(fluidState, otherState, direction.getOpposite());
++    }
++
      public void tesselate(BlockAndTintGetter p_234370_, BlockPos p_234371_, VertexConsumer p_234372_, BlockState p_234373_, FluidState p_234374_) {
          boolean flag = p_234374_.is(FluidTags.LAVA);
 -        TextureAtlasSprite[] atextureatlassprite = flag ? this.lavaIcons : this.waterIcons;
@@ -20,6 +41,25 @@
          float f = (float)(i >> 16 & 0xFF) / 255.0F;
          float f1 = (float)(i >> 8 & 0xFF) / 255.0F;
          float f2 = (float)(i & 0xFF) / 255.0F;
+@@ -87,12 +_,12 @@
+         FluidState fluidstate4 = blockstate4.getFluidState();
+         BlockState blockstate5 = p_234370_.getBlockState(p_234371_.relative(Direction.EAST));
+         FluidState fluidstate5 = blockstate5.getFluidState();
+-        boolean flag1 = !isNeighborSameFluid(p_234374_, fluidstate1);
+-        boolean flag2 = shouldRenderFace(p_234374_, p_234373_, Direction.DOWN, fluidstate) && !isFaceOccludedByNeighbor(Direction.DOWN, 0.8888889F, blockstate);
+-        boolean flag3 = shouldRenderFace(p_234374_, p_234373_, Direction.NORTH, fluidstate2);
+-        boolean flag4 = shouldRenderFace(p_234374_, p_234373_, Direction.SOUTH, fluidstate3);
+-        boolean flag5 = shouldRenderFace(p_234374_, p_234373_, Direction.WEST, fluidstate4);
+-        boolean flag6 = shouldRenderFace(p_234374_, p_234373_, Direction.EAST, fluidstate5);
++        boolean flag1 = !isNeighborStateHidingOverlay(p_234374_, blockstate1, Direction.DOWN);
++        boolean flag2 = shouldRenderFace(p_234374_, p_234373_, Direction.DOWN, blockstate) && !isFaceOccludedByNeighbor(Direction.DOWN, 0.8888889F, blockstate);
++        boolean flag3 = shouldRenderFace(p_234374_, p_234373_, Direction.NORTH, blockstate2);
++        boolean flag4 = shouldRenderFace(p_234374_, p_234373_, Direction.SOUTH, blockstate3);
++        boolean flag5 = shouldRenderFace(p_234374_, p_234373_, Direction.WEST, blockstate4);
++        boolean flag6 = shouldRenderFace(p_234374_, p_234373_, Direction.EAST, blockstate5);
+         if (flag1 || flag2 || flag6 || flag5 || flag3 || flag4) {
+             float f3 = p_234370_.getShade(Direction.DOWN, true);
+             float f4 = p_234370_.getShade(Direction.UP, true);
 @@ -180,15 +_,15 @@
                  float f57 = f4 * f;
                  float f29 = f4 * f1;

src/main/java/net/neoforged/neoforge/common/extensions/IBlockExtension.java

@@ -1019,4 +1019,16 @@ default BubbleColumnDirection getBubbleColumnDirection(BlockState state) {
             return BubbleColumnDirection.NONE;
         }
     }
+
+    /**
+     * Determines if a fluid adjacent to the block on the given side should not be rendered.
+     * 
+     * @param state         the block state of the block
+     * @param selfFace      the face of this block that the fluid is adjacent to
+     * @param adjacentFluid the fluid that is touching that face
+     * @return true if this block should cause the fluid's face to not render
+     */
+    default boolean shouldHideAdjacentFluidFace(BlockState state, Direction selfFace, FluidState adjacentFluid) {
+        return state.getFluidState().getType().isSame(adjacentFluid.getType());
+    }
 }

src/main/java/net/neoforged/neoforge/common/extensions/IBlockStateExtension.java

@@ -755,4 +755,15 @@ default boolean isEmpty() {
     default BubbleColumnDirection getBubbleColumnDirection() {
         return self().getBlock().getBubbleColumnDirection(self());
     }
+
+    /**
+     * Determines if a fluid adjacent to the block on the given side should not be rendered.
+     * 
+     * @param selfFace      the face of this block that the fluid is adjacent to
+     * @param adjacentFluid the fluid that is touching that face
+     * @return true if this block should cause the fluid's face to not render
+     */
+    default boolean shouldHideAdjacentFluidFace(Direction selfFace, FluidState adjacentFluid) {
+        return self().getBlock().shouldHideAdjacentFluidFace(self(), selfFace, adjacentFluid);
+    }
 }

tests/src/generated/resources/assets/neotests_test_water_glass_face_removal/blockstates/water_glass.json

@@ -0,0 +1,7 @@
+{
+  "variants": {
+    "": {
+      "model": "neotests_test_water_glass_face_removal:block/water_glass"
+    }
+  }
+}

tests/src/generated/resources/assets/neotests_test_water_glass_face_removal/lang/en_us.json

@@ -0,0 +1,3 @@
+{
+  "block.neotests_test_water_glass_face_removal.water_glass": "Water Glass"
+}

tests/src/generated/resources/assets/neotests_test_water_glass_face_removal/models/block/water_glass.json

@@ -0,0 +1,7 @@
+{
+  "parent": "minecraft:block/cube_all",
+  "render_type": "minecraft:cutout",
+  "textures": {
+    "all": "minecraft:block/glass"
+  }
+}

tests/src/main/java/net/neoforged/neoforge/debug/fluid/ClientFluidTests.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) NeoForged and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.neoforged.neoforge.debug.fluid;
+
+import net.minecraft.client.renderer.block.LiquidBlockRenderer;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.gametest.framework.GameTest;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.TransparentBlock;
+import net.minecraft.world.level.block.state.BlockBehaviour;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.material.FluidState;
+import net.minecraft.world.level.material.Fluids;
+import net.neoforged.api.distmarker.Dist;
+import net.neoforged.neoforge.client.model.generators.BlockStateProvider;
+import net.neoforged.testframework.DynamicTest;
+import net.neoforged.testframework.annotation.ForEachTest;
+import net.neoforged.testframework.annotation.TestHolder;
+import net.neoforged.testframework.gametest.EmptyTemplate;
+import net.neoforged.testframework.registration.RegistrationHelper;
+
+@ForEachTest(groups = ClientFluidTests.GROUP, side = Dist.CLIENT)
+public class ClientFluidTests {
+    public static final String GROUP = "level.fluid.client";
+
+    static class WaterGlassBlock extends TransparentBlock {
+        private static final Direction HIDE_DIRECTION = Direction.NORTH;
+
+        public WaterGlassBlock(Properties p_309186_) {
+            super(p_309186_);
+        }
+
+        @Override
+        public boolean shouldHideAdjacentFluidFace(BlockState state, Direction selfFace, FluidState adjacentFluid) {
+            if (selfFace == HIDE_DIRECTION) {
+                return adjacentFluid.getFluidType() == Fluids.WATER.getFluidType();
+            } else {
+                return super.shouldHideAdjacentFluidFace(state, selfFace, adjacentFluid);
+            }
+        }
+    }
+
+    @GameTest
+    @EmptyTemplate
+    @TestHolder(description = "Tests if blocks can prevent neighboring fluids from rendering against them")
+    static void testWaterGlassFaceRemoval(final DynamicTest test, final RegistrationHelper reg) {
+        final var glass = reg.blocks().registerBlock("water_glass", WaterGlassBlock::new, BlockBehaviour.Properties.ofFullCopy(Blocks.GLASS)).withLang("Water Glass").withBlockItem();
+        reg.provider(BlockStateProvider.class, prov -> prov.simpleBlock(glass.get(), prov.models()
+                .cubeAll("water_glass", ResourceLocation.withDefaultNamespace("block/glass"))
+                .renderType("cutout")));
+        final var waterPosition = new BlockPos(1, 1, 2);
+        final var glassDirection = WaterGlassBlock.HIDE_DIRECTION.getOpposite();
+        final var glassPosition = waterPosition.relative(glassDirection);
+        test.onGameTest(helper -> helper.startSequence()
+                .thenExecute(() -> helper.setBlock(glassPosition, glass.get().defaultBlockState()))
+                .thenExecute(() -> helper.setBlock(waterPosition, Blocks.WATER.defaultBlockState()))
+                // Check that the north side of the water is not rendered
+                .thenExecute(() -> helper.assertFalse(
+                        LiquidBlockRenderer.shouldRenderFace(
+                                helper.getBlockState(waterPosition).getFluidState(),
+                                helper.getBlockState(waterPosition),
+                                glassDirection,
+                                helper.getBlockState(glassPosition)),
+                        "Fluid face rendering is not skipped"))
+                .thenSucceed());
+    }
+}