Leveller(tm) - Daylon Graphics

If you're new to Leveller, or to pixel-based editors in general, then this tutorial is for you. It covers the basics of using the Leveller tools to sculpt a heightfield.

Leveller's user interface was influenced by Paint Shop Pro 4 and Adobe Photoshop. If you use either of those programs, you'll probably see the similarities. We wanted to make it easy for users of other graphics software to use Leveller.

A heightfield, like a bitmap, is composed of discrete point samples called pixels. Instead of a color, however, each pixel contains an elevation value. Heightfields are discussed in more depth here.

Most of Leveller's editing tools use a setting called the current brush size. This is simply a number which specifies how wide, in pixels, the region under the mouse pointer will be affected when a tool is used.

The spatial reference system used is based on simple cartography. In painting, one uses words like "top" to mean the first scanline of a bitmap. With heightfields, however, "top" could also mean the top of a peak. As the diagram below shows, the preferred nomenclature is to use compass directions.

The north-south distance is the heightfield's breadth, because using the word "height" could mean the elevation height. Speaking of which, the distance from the lowest elevation to the highest is called the span.

Like a paint program, Leveller makes extensive use of selection masks. These are simply user-defined regions of the heightfield that control where sculpting and filtering effects can occur. The picture below shows an example of a discontinuous selection mask, because the selected regions are not connected to each other.

Naturally, a selection mask is also composed of pixels. Since each such pixel has an 8-bit value, it is possible to make the mask behave as an alpha channel, where some regions are "more selected" than others. For example, if you "strongly selected" one area and "lightly selected" another, and then proceeded to use the Dig tool, the latter region wouldn't be dug as deeply as the former.

By default, Leveller documents start off with no selection mask, which means that every heightfield pixel is fully selected. As you use the editing tools, however, you will want to use masks to assert more control and make fine-tuned edits.

Selection masks are also used to support the Cut/Copy/Paste commands in the Edit menu. To copy the entire heightfield to the clipboard, for example, you would choose Selection, Select All, and then Edit, Copy.

Selections are also used to control object placement in the POV-Ray export. The forest tutorial explains how.

And finally, there is the colormap. This is simply how heightfields are colored so that you can tell (when looking from overhead, anyway), which parts have which elevations. You can use the View, Colormap... command to choose which colormap to use.

The primary editing tools are Dig, Raise, and Flatten (also, when you use the Delete key to flatten the currently selected area, it is the elevation setting of the Flatten tool that is used). These tools directly modify the elevation of heightfield pixels wherever the mouse is dragged over the map, between pushing the mouse button down and releasing it.

Every tool has a tool settings panel. This lets you customize the tool to work a certain way.

	Rectangular Select	Makes rectangular selections. Click and drag to define the rectangle's opposing corners. The tool settings let you constrain the rectangle to a square or to a line.
	Elliptical Select	Makes oval-shaped selections. Click and drag to define the containing rectangle's opposing corners. The tool settings let you constrain the oval to a circle or to an ellipse of specific thickness.
	Arbitrary Select	Makes irregular-shaped selections. Click and drag to define the border of the selected region. When the mouse is released, the starting/ending points of the mousedrag will be joined by a straight line.
	Magic Wand	Selects areas of similar elevation. Simply define the tool settings and click on a heightfield pixel to create the selection.

When selecting, hold the Shift key down to extend the current selection. Hold the Ctrl key down to subtract from the current selection.

All the selection tools create "fully selected" regions. To make the edges of the selection "lightly selected", use the Selection, Feather command. You can modify the current selection mask in more ways with the other commands in the Selection menu.

Filters are processes that work on all the pixels within the current selection at once. This makes them faster than doing the same process with the editing tools. Judicious mixing of filters, tools, and selection masks, of course, makes for very powerful modeling.

The filters are available in the Filter menu. The first bunch are "core" filters because they are built-in to Leveller itself; the rest are plug-in based, so their availability depends on which plug-ins have been installed.

The core filters do fundamental operations, such as inversion, flipping, scaling, rotation, clipping, combining, etc. The pictures below show the effects of the Clip, Slide, and Terrace filters.