Decals

A decal projects a material onto the surfaces it reaches (GameObject > Chisel > Create Decal, or Add Component > Chisel > Decal).

• Box decals project their image through a box, in the direction its blue (forward) arrow points. Surfaces turned further than the Max Angle from the direction the image comes from don't take it.
• Projection: orthographic keeps the image's size at every depth; perspective projects it from a point behind the box, like a projector (with a field of view).
• Transparent decals are drawn over the surfaces they cover. Opaque decals replace the surface where they cover it; collisions aren't affected.
• Repeat (x and y) repeats the image across the box.
• Image: the whole texture, or a tile of the material's hotspot layout (an image in a trim sheet), picked from the layout. A tile can't repeat by wrapping, so a repeated tile becomes a tile of the box for every image, the last row and column cut short.
• Target limits a decal to one surface of a brush (or all of one brush's surfaces).
• A decal belongs to the model it is a child of; a decal outside any model draws on every model in its scene.
• Overlapping transparent decals are drawn in the order of the hierarchy.
• Decals become part of the level's surfaces, so they follow them when you change the shapes.

Polygon decals

A polygon decal fills an outline on one surface, any outline that doesn't cross itself. Set the decal's Shape to Polygon, or draw one:

• With the Surface Shape tool, click the shape's corners on a surface; they snap to its grid, and to the surface's corners and edges. Click the first corner again to close it. Escape drops the shape being drawn.
• The shape becomes a polygon decal of the surface's brush, limited to that surface, with the surface's material and texture coordinates until you give it its own.

Its settings:

• Brush and Surface: the surface the shape is on.
• Depth: how far the shape reaches either side of its surface, together.
• Surface UVs: the texture coordinates of the surface it is on instead of the image's, so its material lines up with the surface's texturing.
• Extrude Out makes the shape a brush on its surface, Extrude Height tall, that adds to its brush. Push In makes it a brush that cuts into its brush.

See also Trim Decals and Hotspot Mapping.