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Half-Life level design: Vertex manipulation

Vertex manipulation can easily lead to unexpected compiler errors when used without some practice. This tutorial shows how the tool works and how the common errors can be avoided.

Basics

  1. Create a normal cube brush.
  2. Enable the vertex manipulation mode by clicking on its icon vertex_icon1.gif. The cube changes its appearance to suit this mode.
    vertex_basics1.png
  3. Click down your left mouse button on a dot at any corner and drag it sideways. When you're done moving it a bit, the result should show up as something like this:
    vertex_basics2.png
  4. Finalize your changes by selecting the cursor icon vertex_icon2.gif. The brush now takes its manipulated form.
    vertex_basics3.png

Adding more vertices

  1. Use the clip tool vertex_icon3.gif to a corner of your brush.
    vertex_adding1.png
  2. You'll instantly have one more vertex to play with. You might want to move one of the new vertices back to where the original one used to be. Here's a quick rounded corner made with just two steps:
    vertex_adding2.png

Creating a foolproof brush

This kind of brush can be used to create bumpy terrain or other complex objects without causing compiler errors. Using a foolproof brush can make things a lot easier for you if you're not very experienced with vertex manipulation.

  1. Use the clip tool or just vertex manipulate a cube into an object that has a total of 5 faces and looks like a triangle when you look at it in the top viewport.
    vertex_foolproof1.png
  2. Move two of the vertices together over a third vertex on the same plane. See the image below for guidance, and note that you'll need to select the vertices separately, not just by directly moving them in the top viewport. To do this, use the 3D view to select a vertex and then you can move it around separately in the top view. Remember to answer Yes to the "Merge vertices?" dialog that pops up for both.
    vertex_foolproof2.png
  3. After doing all this, finalize your modifications. The brush should look like a triangle in each of the 2D viewports, and as a quarter of a pyramid in 3D.

Common errors and troubleshooting

It's important to realize that all corners of a vertex manipulated face have to be on the same plane, and faces shouldn't intersect with other faces of the same brush. So something like this isn't going to work:
vertex_errors1.png

Error in VIS: Leaf saw into leaf

Warning: Leaf portals saw into leaf Problem at portal between leaves 1027 and 1059:
(1324.923 2172.988 -40.000)
(1325.000 2173.000 -39.833)
(1325.000 2173.000 -34.133)
(1318.000 2171.923 -27.097)
(1318.000 2171.923 -40.000)

This error is almost exclusively caused by vertex manipulations that went wrong. This happens when a brush can "see" into itself by having a concave part in it, like shown here:

vertex_errors2-1.png

You can easily replicate this shape with two brushes placed like this:

vertex_errors2-2.png

Error in CSG: Coplanar plane

Entity 0, Brush 99, Side 3: has a coplanar plane at (-64, -64, -64), texture AS

This error comes up when you have a brush that has been vertex manipulated to have more than one of its faces on the same plane, similar to this example:

vertex_errors3.png

You can fix this by moving the extra vertices over to either side and answering Yes when the editor prompts you with the question "Merge Vertices?"

Error in CSG: Outside world

Error: Entity 0, Brush 152: outside world(+/-4096): (-9907,-614,-247)-(-1927,7865,-208)

Vertex manipulation can also cause this error when a vertex is not on the same plane as the rest of the face's vertices. A telltale sign of this is that some of the coordinates in the error message are way beyond +/- 4096. The problem you're looking for in a brush looks something like this:

vertex_errors4.png

Problems like this cause the compilers to compensate and recalculate the vertices' positions, making the brush stretch far beyond the normal boundaries.

If the problematic shape was created on purpose, it's better to try redoing it with two or more brushes.