Fix experimental lighting pipeline breaking vanilla's emissive rendering. Closes #9552 (#9582)

src/main/java/net/minecraftforge/client/model/lighting/FlatQuadLighter.java

@@ -38,9 +38,10 @@ public class FlatQuadLighter extends QuadLighter
         isFullCube = Block.isShapeFullBlock(state.getCollisionShape(level, pos));
         for (Direction side : SIDES)
         {
-            packedLight[side.ordinal()] = LevelRenderer.getLightColor(level, pos.relative(side));
+            packedLight[side.ordinal()] = getLightColor(level, pos.relative(side), state);
         }
-        packedLight[6] = LevelRenderer.getLightColor(level, pos);
+        //Note: We can just use the LevelRenderer method as we know the state is the state at the given position
+        packedLight[6] = LevelRenderer.getLightColor(level, state, pos);
     }
 
     @Override

src/main/java/net/minecraftforge/client/model/lighting/QuadLighter.java

@@ -8,9 +8,11 @@ package net.minecraftforge.client.model.lighting;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.mojang.blaze3d.vertex.VertexConsumer;
 import net.minecraft.client.color.block.BlockColors;
+import net.minecraft.client.renderer.LightTexture;
 import net.minecraft.client.renderer.block.model.BakedQuad;
 import net.minecraft.core.BlockPos;
 import net.minecraft.world.level.BlockAndTintGetter;
+import net.minecraft.world.level.LightLayer;
 import net.minecraft.world.level.block.state.BlockState;
 import org.joml.Vector3f;
 
@@ -150,4 +152,20 @@ public abstract class QuadLighter
         float yFactor = constantAmbientLight ? 0.9F : ((3.0F + normalY) / 4.0F);
         return Math.min(normalX * normalX * 0.6F + normalY * normalY * yFactor + normalZ * normalZ * 0.8F, 1.0F);
     }
+
+    /**
+     * Note: This method is subtly different than {@link net.minecraft.client.renderer.LevelRenderer#getLightColor(BlockAndTintGetter, BlockState, BlockPos)}
+     * as it only uses the state for querying if the state has emissive rendering but instead looks up the state at the given position for checking the
+     * light emission.
+     */
+    protected static int getLightColor(BlockAndTintGetter level, BlockPos pos, BlockState state)
+    {
+        if (state.emissiveRendering(level, pos))
+        {
+            return LightTexture.FULL_BRIGHT;
+        }
+        int skyLight = level.getBrightness(LightLayer.SKY, pos);
+        int blockLight = Math.max(level.getBrightness(LightLayer.BLOCK, pos), level.getBlockState(pos).getLightEmission(level, pos));
+        return skyLight << 20 | blockLight << 4;
+    }
 }

src/main/java/net/minecraftforge/client/model/lighting/SmoothQuadLighter.java

@@ -50,7 +50,7 @@ public class SmoothQuadLighter extends QuadLighter
                     pos.setWithOffset(origin, x - 1, y - 1, z - 1);
                     BlockState neighborState = level.getBlockState(pos);
                     t[x][y][z] = neighborState.getLightBlock(level, pos) < 15;
-                    int brightness = LevelRenderer.getLightColor(level, pos);
+                    int brightness = getLightColor(level, pos, state);
                     s[x][y][z] = LightTexture.sky(brightness);
                     b[x][y][z] = LightTexture.block(brightness);
                     ao[x][y][z] = neighborState.getShadeBrightness(level, pos);