This article relates to the game "Half-Life: Alyx". Click here for more information.
This article relates to the workshop tools for "Half-Life: Alyx". Click here for more information.
This article's documentation is for Source 2. Click here for more information.


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This tutorial will teach you how to create doors for HL:A based mods. This doors will can be opened by grabbing the door knob and moving it forward or backwards.


Create two rooms, with a height of at least 128 units, and separated by 8 units.

HLA SDK Doors Img1.png

Insert a prop_static entity and, for this tutorial, select the model models/architecture/doors_1/door_frame_basic_001.vmdl.

HLA SDK Doors Img2.png

Select the two faces that connect the rooms and clip them using the door frame as a reference. Remove the faces inside the frame. (Note: If you want to prevent issues with texture alignment when subdividing later on, select the faces you plan on cutting holes in, and separate them from the rest of the room with Alt+N. Then, when cutting, cut along the entire length and height of the face, instead of just along the edge of the doorframe.)

HLA SDK Doors Img3.png

Insert a prop_door_rotating_physics entity and, for this tutorial, select the model models/architecture/doors_1/door_1a_40_92.vmdl.

HLA SDK Doors Img4.png

Switch the grid size to 2 units and align the door with the frame. For realism, change the property Open Direction to either Open Forward Only or Open Backward Only, since real life doors don't open both ways.

HLA SDK Doors Img5.png

Finishing up

Compile and run your map, and you should have a working door.

You can download the example map here [[1]].

HLA SDK Doors Img6.png

Broken subdivisions, and what causes them

When you subdivide faces later on in development, (For example, if you want to use a texture that supports Blend Painting,) if faces were cut without being extracted first, you'll notice that the textures will be warped slightly. This is caused by extra vertices added to the affected face during cutting, turning it from a quad with four vertices to an n-gon that has five or more. You can fix this by deleting the extra vertices.

An example of faces with subdivision, with correct subdivision on the left, vs broken on the right. Note how the face with broken subdivision has a slightly warped texture.

Select the face with broken subdivision, and extract it from the room (Either with the 'Extract Faces' button on the sidebar or by doing Alt+N,) then do Ctrl+H to hide everything but the selected face.

HLA SDK Doors Subdivision Img2.png

Then, in the Vertices selection mode, select and delete any vertices that aren't on the four corners.

HLA SDK Doors Subdivision Img3.png

Press U to unhide the rest of the room, and, in the Meshes selection mode, select both the newly fixed face and the room with Shift+Left-click, then press M (Or click on the 'Merge Meshes' button on the sidebar to the left.)

HLA SDK Doors Subdivision Img4.png

Repeat the process with any other affected faces, and your textures should be aligned properly again.

HLA SDK Doors Subdivision Img5.png