Normal maps

Source, result, knobs

Open a height map and run :set editor normalmap. Three windows come up: the source you started from, the result split to its right at the same zoom, and the form as a sidebar down the right edge — the mirror of where the file tree goes. Focus lands on the form, because the knobs are the point.

height.png The normal map generator 1 / 6 play

1. start A height map: grey, and not what a shader wants.
2. 1 :set editor normalmapEnter The result appears beside the source, with a form of knobs at the right edge.
3. 2 jl j and k pick a knob, h and l turn it — the map redraws as you go.
4. 3 :tool normalmap strength 3Enter Every knob is an ex command too.
5. 4 Ctrl-W h:wEnter Ctrl-W h from the form onto the result, then :w. The window was named height_normal.png from the moment the tool opened, so a bare :w puts the map beside its height map. :w in the form has no file to write and says no file name for %.
6. 5 Ctrl-W h:set editor imageEnter Ctrl-W h again onto the source, and :set editor image closes the result and the form together. The height map has the window to itself, unchanged — the tool never wrote into it.

Source and result sit side by side deliberately: every knob is recomputed synchronously and the picture re-uploads, so turning Strength shows its effect immediately. A large sheet with a wide blur will feel that; it is the honest cost of a live picture.

The knobs

Map        ‹ normal ›            what the result shows: normal | displacement
Strength   ━━━━━●━━━━   2.5      slope scale, 0.1..20
Level      ━━━━━━●━━━   1.0      gamma on the height, 0.1..10
Blur       ●━━━━━━━━━   0        gaussian sigma on the height, 0..32 pixels
Filter     ‹ sobel ›             sobel | scharr | prewitt
Height     ‹ luma ›              luma | r | g | b | a
Invert R   [ ]
Invert G   [ ]
Invert H   [ ]                   the height itself
Z range    ‹ -1..1 ›             -1..1 | 0..1

The form takes the keys every form takes: j and k pick a field, h and l turn it, H and L by ten, Space toggles a bool or cycles a choice, Enter puts the field on the ex line, and u undoes a change. Tab anywhere in the form flips which map the result shows.

Every field is also a command, and reports without a value, so a preset is a line in a script:

What it computes

1. Height from the source — luma, or one channel, as 0..1 floats; inverted if asked; blurred by the Blur sigma.
2. Level is a gamma on that height, so the same slopes can be pushed toward the peaks or the floor.
3. Gradient by the chosen 3×3 filter — Sobel, Scharr or Prewitt — with the edges clamped.
4. Normal is normalize(-dx·strength, -dy·strength, 1), with R or G flipped if asked, encoded as rgb = n·0.5 + 0.5. With Z range at 0..1, blue is z itself.
5. Displacement is the levelled height as grey, alpha opaque.

Ambient occlusion and specular are not built yet; they are the next maps and slot into the same form.

Writing the result

The result window’s image is named for its output from the start — atlas_normal.png beside atlas.png, atlas_disp.png for displacement — so :w there writes the map where you would expect it, and :w other.png names another place.

Run :w from the result, not from the form: the form is a window with no file behind it, and it answers no file name for %.

A result is never dirty — it is derived, so :q on it asks nothing. The source is dirty only if you edit the source.

Leaving

q in the form closes the result and the form and forgets the tool, and so does :set editor image on the source. Closing either of those windows by hand does the same. Closing the source leaves them standing as a plain picture and a plain form, since what they show is still on screen and taking it away would be a surprise. :set editor normalmap on a window that already has the tool just focuses its form.