Brush Tools Vertex

While Resize mode is about moving brushes within a scene, Vertex mode is about moving the parts of a brush. There is some overlap between Vertex mode and Resize mode, but Vertex mode offers more options, like creating sloped surfaces and other complex geometry.

Most interesting level geometry has more angles to it than are possible with Resize mode alone, which is why most of the work on a level past the earliest blocking phase will rely at least to some extent on Vertex mode.

Selecting and Deselecting

Selecting a brush in Vertex mode is similar to how selection works in Resize mode. You can select a brush behind another brush by clicking repeatedly and cycling through the brushes at that position. However, because Vertex mode let you select edges and vertices, if you try to cycle through multiple brushes, you may instead accidentally select part of a brush. Because of this, sometimes it is easier to move the camera and select a brush than to try cycling through a series of brushes to select the one you want. Sometimes it may also be faster to use Resize mode for selection, and then Vertex mode for editing. To deselect part of a brush without deselecting the brush, you can click one of the brush’s faces.

Once you have a brush selected, handles will appear at each vertex. Clicking a handle will select its vertex, and holding Shift while clicking will let you include more vertices in the selection. To remove a vertex from a selected group, you can hold Ctrl and click the handle.

Vertex mode also allows for marquee selection; click and drag, and the vertices within the marquee when you release will become a group selection. It is also possible to select vertices by clicking on the selected brush’s edges; this will select both vertices that produce the edge.

Marquee selection in Vertex mode

If your scene camera is set to isometric mode and is axis aligned—effectively creating a 2D view of the environment—then one vertex may be directly behind another. For example, if the camera is looking down on a cuboid, then it will appear to be a square. To select both the near and far vertices, you must marquee. Clicking a vertex in this view will only select the nearest one, which in this example would be on the top of the brush.

Vertex Movement

After one or more vertices are selected, a movement handle will appear, allowing you to move the selection. To build angled or sloped structures, it is typically best to modify a brush’s vertices in groups of two. For example, to make a ramp from a cuboid, you can select one of the bottom edges and move it away from the base. Trying to create ramps or other complex volumes by moving one vertex at a time adds more room for human error, and can make the brush concave.

Vertex Editing

Creating a ramp with Vertex mode

To move an entire brush in vertex mode, you can marquee all of its vertices, and then use the movement handle. Often, if you are already in Vertex mode, it is can be faster to move a brush this way than by switching to Resize mode and moving the brush there. The movement handle in Vertex mode is also an easy way to move a brush along one axis at a time.

Moving a brush in Vertex mode

Concave Warnings

Sometimes in vertex mode you may encounter a concave warning. This happens in two situations, when an edge creates a concavity in the brush (by making a C shape for example) or when one or more of the vertices that comprise a face no longer shares the same plane as the other vertices of that face (even if the face appears to be convex). When SabreCSG detects that a brush is concave, the brush will turn red and warning text will appear below the tool selection bar. SabreCSG does not currently support concave brushes, so trying to rebuild a level that has concave warnings may cause errors.

If the geometry you are building needs to be concave, such as an arch, you should build it from multiple brushes. A quick way to turn a concave brush into two convex brushes is to split it using the Clip tool.

Additionally if you need to move a specific vertex off the plane of the polygon, you should use vertex connection to split the face, as shown in this animation:

Making a concave brush convex

Snapping Vertices to Grid

Vertex mode also allows you to snap selected vertices to the global grid or the grid local to the brush. Both these tools are useful in certain situations and can be carried out by selecting vertices then clicking the Global Snap or Local Snap button respectively.

In typical vertex editing, you won’t need to use this button often, since vertices already snap to the grid. However, with more complicated brush work, or when adjusting the vertices of rotated brushes, this tool can help. For example, to build an approximate spiral staircase, you can use prisms as guides, where the vertices of the prism are snapped to a low grid setting, like 0.125.

If the grid setting is too high, snapping can move vertices to the same position. These vertices will be merged when you rebuild, so it’s important to make sure the positional snapping value is appropriate.

Creating Edges by Connecting Vertices

As shown in the concavity animation, you can create new edges between two vertices on the same polygon by selecting the two vertices and clicking the connect button. The vertices cannot be neighbours (that is there must be a vertex between them on the loop) as they already share an edge. This feature is particularly useful if you need to adjust specific vertices or split faces without the clip tool. Note that you can also create new edges by connecting the mid-points of two edges in the edge tool.

Welding vertices

Occasionally it’s useful to weld vertices together into single merged vertices. SabreCSG has a number of merge tools to achieve this, in the vertex tool there is a button for Weld Selection to Mid-Point which takes the selected vertices, calculates their averaged center then combines all the selected vertices into a single vertex at the averaged centre. One particular example of using this would be to convert a cube into a square-based-pyramid by selecting the top four vertices and clicking Weld Selection to Mid-Point.

Welding vertices to their mid-point

In addition you can also do a tolerance weld, which takes a distance then welds any of the selected vertices which are within the specified distance to each other.

Welding vertices with a tolerance

Finally you can merged vertices by moving them to overlap existing vertices and when you click rebuild the vertices will automatically be merged and extraneous polygons, edges and vertices will be stripped out.

In addition you can create new edges by selecting two edges and clicking the split button. This will split the edges at their mid-points and create a new edge connecting the two new points.

Splitting two edges to create a new edge

Chamfer Edges

The Chamfer tool allows you to create chamfered or beveled corners to brush geometry. A chamfer is an effect that smooths out edges and corners. Chamfers are useful for giving realism to non-organic models. In the real world, the blunt edges on objects catch the light and change the shading around the edges. This gives a solid, realistic look, as opposed to un-chamfered objects which can look too perfect.

You can right-click the "Chamfer" button to open a tool settings popup window. The distance defines how deep the chamfer digs into the brush. Having "0.1" means it will round the edge 10cm into the brush. The amount of iterations determines how detailed the chamfer is (e.g. 1 is a simple bevel).

Please keep in mind that this tool uses clipping planes to slice off corners. These cuts could possibly affect portions of the brush that are not directly related to the edge (for example, if you split an edge and chamfer one side of it, the other side will also be affected).

Chamfering some edges of a cube