Stairs have buggy ambient occlusion #721
Description
Describe the bug
Stairs which are not hit by block light have buggy ambient occlusion for me. I tested it in two environments: a one where I had 20 mods and one that had only VulkanMod.
Steps to reproduce
Place down any kind of stair far from a light source.
Log files
[14:43:54] [main/INFO]: Loading Minecraft 1.21.11 with Fabric Loader 0.18.4
[14:43:54] [main/INFO]: Fabric is preparing JARs on first launch, this may take a few seconds...
[14:43:54] [main/INFO]: Loading 27 mods:
- fabricloader 0.18.4
-- mixinextras 0.5.0
- java 21
- minecraft 1.21.11
- vulkanmod 0.5.8
|-- fabric-api-base 1.0.5+4ebb5c083e
|-- fabric-block-view-api-v2 1.0.39+4ebb5c083e
|-- fabric-lifecycle-events-v1 2.6.15+4ebb5c083e
|-- fabric-renderer-api-v1 8.0.0+f4ffd2e53e
|-- fabric-rendering-fluids-v1 3.1.43+4ebb5c083e
|-- fabric-rendering-v1 16.2.7+f4ffd2e53e
|-- fabric-resource-loader-v0 3.3.4+4fc5413f3e
|-- fabric-resource-loader-v1 1.0.10+78c8b4663e
|-- fabric-transitive-access-wideners-v1 7.0.8+0107c3da3e
|-- org_lwjgl_lwjgl-shaderc 3.3.3
|-- org_lwjgl_lwjgl-shaderc_natives-linux 3.3.3
|-- org_lwjgl_lwjgl-shaderc_natives-macos 3.3.3
|-- org_lwjgl_lwjgl-shaderc_natives-macos-arm64 3.3.3
|-- org_lwjgl_lwjgl-shaderc_natives-windows 3.3.3
|-- org_lwjgl_lwjgl-vma 3.3.3
|-- org_lwjgl_lwjgl-vma_natives-linux 3.3.3
|-- org_lwjgl_lwjgl-vma_natives-macos 3.3.3
|-- org_lwjgl_lwjgl-vma_natives-macos-arm64 3.3.3
|-- org_lwjgl_lwjgl-vma_natives-windows 3.3.3
|-- org_lwjgl_lwjgl-vulkan 3.3.3
|-- org_lwjgl_lwjgl-vulkan_natives-macos 3.3.3
-- org_lwjgl_lwjgl-vulkan_natives-macos-arm64 3.3.3
[14:43:54] [main/INFO]: SpongePowered MIXIN Subsystem Version=0.8.7 Source=file:/C:/Users/{COMPUTER_USERNAME}/AppData/Roaming/ModrinthApp/meta/libraries/net/fabricmc/sponge-mixin/0.17.0+mixin.0.8.7/sponge-mixin-0.17.0+mixin.0.8.7.jar Service=Knot/Fabric Env=CLIENT
[14:43:55] [main/INFO]: Compatibility level set to JAVA_21
[14:43:56] [main/INFO]: Initializing MixinExtras via com.llamalad7.mixinextras.service.MixinExtrasServiceImpl(version=0.5.0).
[14:43:56] [Datafixer Bootstrap/INFO]: 287 Datafixer optimizations took 362 milliseconds
[14:44:00] [Render thread/INFO]: Environment: Environment[sessionHost=https://sessionserver.mojang.com, servicesHost=https://api.minecraftservices.com, profilesHost=https://api.mojang.com, name=PROD]
[14:44:00] [Render thread/INFO]: Setting user: {MINECRAFT_USERNAME}
[14:44:00] [Render thread/INFO]: == VulkanMod ==
[14:44:00] [Render thread/INFO]: Selecting Platform: WIN32
[14:44:00] [Render thread/INFO]: GLFW: 3.4.0 Win32 WGL Null EGL OSMesa VisualC DLL
[14:44:00] [Render thread/INFO]: Backend library: LWJGL version 3.3.3-snapshot
[14:44:01] [Render thread/INFO]: Using optional rendering extensions:
[14:44:01] [Render thread/INFO]: Reloading ResourceManager: vanilla, fabric-api-base, fabric-block-view-api-v2, fabric-lifecycle-events-v1, fabric-renderer-api-v1, fabric-rendering-fluids-v1, fabric-rendering-v1, fabric-resource-loader-v0, fabric-resource-loader-v1, fabric-transitive-access-wideners-v1, fabricloader, vulkanmod
[14:44:01] [Worker-Main-2/ERROR]: Invalid path in mod resource-pack vulkanmod: vulkanmod:shaders/basic/terrain_earlyZ/terrain_earlyZ.json, ignoring
[14:44:01] [Worker-Main-2/ERROR]: Invalid path in mod resource-pack vulkanmod: vulkanmod:shaders/basic/terrain_earlyZ/terrain_earlyZ.fsh, ignoring
[14:44:01] [Worker-Main-13/INFO]: Found unifont_all_no_pua-17.0.01.hex, loading
[14:44:01] [Worker-Main-3/INFO]: Found unifont_pua-17.0.01.hex, loading
[14:44:01] [Worker-Main-12/INFO]: Found unifont_jp_patch-17.0.01.hex, loading
[14:44:02] [Render thread/INFO]: OpenAL initialized on device OpenAL Soft on Speakers (Razer BlackShark V2 HS 2.4)
[14:44:02] [Render thread/INFO]: Sound engine started
[14:44:02] [Render thread/INFO]: Created: 512x256x0 minecraft:textures/atlas/particles.png-atlas
[14:44:02] [Render thread/INFO]: Created: 128x128x0 minecraft:textures/atlas/decorated_pot.png-atlas
[14:44:02] [Render thread/INFO]: Created: 2048x1024x0 minecraft:textures/atlas/armor_trims.png-atlas
[14:44:02] [Render thread/INFO]: Created: 512x256x0 minecraft:textures/atlas/paintings.png-atlas
[14:44:02] [Render thread/INFO]: Created: 1024x512x0 minecraft:textures/atlas/shield_patterns.png-atlas
[14:44:02] [Render thread/INFO]: Created: 2048x2048x4 minecraft:textures/atlas/blocks.png-atlas
[14:44:02] [Render thread/INFO]: Created: 512x512x0 minecraft:textures/atlas/chest.png-atlas
[14:44:02] [Render thread/INFO]: Created: 256x128x0 minecraft:textures/atlas/celestials.png-atlas
[14:44:02] [Render thread/INFO]: Created: 1024x512x0 minecraft:textures/atlas/banner_patterns.png-atlas
[14:44:02] [Render thread/INFO]: Created: 512x512x0 minecraft:textures/atlas/beds.png-atlas
[14:44:02] [Render thread/INFO]: Created: 1024x512x0 minecraft:textures/atlas/items.png-atlas
[14:44:02] [Render thread/INFO]: Created: 1024x1024x0 minecraft:textures/atlas/gui.png-atlas
[14:44:02] [Render thread/INFO]: Created: 128x64x0 minecraft:textures/atlas/map_decorations.png-atlas
[14:44:02] [Render thread/INFO]: Created: 512x256x0 minecraft:textures/atlas/signs.png-atlas
[14:44:02] [Render thread/INFO]: Created: 512x512x0 minecraft:textures/atlas/shulker_boxes.png-atlas
[14:44:32] [Render thread/INFO]: Loaded 1470 recipes
[14:44:32] [Render thread/INFO]: Loaded 1584 advancements
[14:44:40] [Server thread/INFO]: Starting integrated minecraft server version 1.21.11
[14:44:40] [Server thread/INFO]: Generating keypair
[14:44:42] [Server thread/INFO]: Selecting global world spawn...
[14:44:44] [Server thread/INFO]: Loading 0 persistent chunks...
[14:44:44] [Server thread/INFO]: Preparing spawn area: 16%
[14:44:44] [Server thread/INFO]: Loading 47 chunks for player spawn...
[14:44:44] [Server thread/INFO]: Preparing spawn area: 16%
[14:44:45] [Server thread/INFO]: Preparing spawn area: 16%
[14:44:45] [Server thread/INFO]: Preparing spawn area: 16%
[14:44:45] [Server thread/INFO]: Preparing spawn area: 16%
[14:44:45] [Server thread/INFO]: Preparing spawn area: 29%
[14:44:45] [Server thread/INFO]: Preparing spawn area: 57%
[14:44:46] [Server thread/INFO]: Time elapsed: 3214 ms
[14:44:46] [Server thread/INFO]: {MINECRAFT_USERNAME}[local:E:91888d26] logged in with entity id 9 at (3.5, 70.0, -2.5)
[14:44:46] [Server thread/INFO]: {MINECRAFT_USERNAME} joined the game
[14:44:46] [Server thread/INFO]: Changing view distance to 16, from 10
[14:44:46] [Server thread/INFO]: Changing simulation distance to 12, from 0
[14:44:46] [Render thread/INFO]: Loaded 2 advancements
[14:44:46] [Render thread/INFO]: Resizing Dynamic Transforms UBO, capacity limit of 2 reached during a single frame. New capacity will be 4.
[14:44:46] [Render thread/INFO]: Resizing Dynamic Transforms UBO, capacity limit of 4 reached during a single frame. New capacity will be 8.
[14:44:51] [Render thread/INFO]: Resizing Dynamic Transforms UBO, capacity limit of 8 reached during a single frame. New capacity will be 16.
[14:45:03] [Render thread/INFO]: [System] [CHAT] Saved screenshot as 2026-01-25_14.45.03.png
[14:45:08] [Render thread/INFO]: [System] [CHAT] Saved screenshot as 2026-01-25_14.45.07.png
[14:45:10] [Server thread/INFO]: Saving and pausing game...
[14:45:10] [Server thread/INFO]: Saving chunks for level 'ServerLevel[New World]'/minecraft:overworld
[14:45:10] [Server thread/INFO]: Saving chunks for level 'ServerLevel[New World]'/minecraft:the_end
[14:45:10] [Server thread/INFO]: Saving chunks for level 'ServerLevel[New World]'/minecraft:the_nether
[14:45:13] [Server thread/INFO]: {MINECRAFT_USERNAME} lost connection: Disconnected
[14:45:13] [Server thread/INFO]: {MINECRAFT_USERNAME} left the game
[14:45:13] [Server thread/INFO]: Stopping singleplayer server as player logged out
[14:45:13] [Server thread/INFO]: Stopping server
[14:45:13] [Server thread/INFO]: Saving players
[14:45:13] [Server thread/INFO]: Saving worlds
[14:45:13] [Server thread/INFO]: Saving chunks for level 'ServerLevel[New World]'/minecraft:overworld
[14:45:14] [Server thread/INFO]: Saving chunks for level 'ServerLevel[New World]'/minecraft:the_end
[14:45:14] [Server thread/INFO]: Saving chunks for level 'ServerLevel[New World]'/minecraft:the_nether
[14:45:14] [Server thread/INFO]: ThreadedAnvilChunkStorage (New World): All chunks are saved
[14:45:14] [Server thread/INFO]: ThreadedAnvilChunkStorage (DIM1): All chunks are saved
[14:45:14] [Server thread/INFO]: ThreadedAnvilChunkStorage (DIM-1): All chunks are saved
[14:45:14] [Server thread/INFO]: ThreadedAnvilChunkStorage: All dimensions are saved
[14:45:17] [Render thread/INFO]: Stopping!
rver
[14:45:13] [Serv