geo/TextureTrace

Draws the outline of every shape in a 2D texture as closed curves, for a logo in relief, a cut-out or a stamp. Send the curves into geo/SDFCreate and geo/SDFExtrude for the shape in relief.

Point `texturePath` at the TEX node showing the picture: a tex/Image, a tex/Text, a tex/Builder. A 3D texture is refused: geo/VolumeFromTexture is the node for those.

**Pick what to trace.** `channel` says which number of each texel is read: red, green, blue, alpha, or the luminance (how bright the texel looks). `level` is where the outline passes, and `inside` says which side of it is the shape. A dark logo on white is luminance, BELOW. A white one on black is ABOVE. A tex/Text over a transparent background is alpha, ABOVE. Colours are read as linear values, the way the renderer reads them, so a mid grey of 128 in the file is about 0.2 here.

**Every curve closes**, even where a shape runs into the edge of the picture: the outline then follows the edge. An outer outline runs counter-clockwise and the outline of a hole clockwise.

**Up in the picture is up in the scene.** The curves lie in the XY plane, with the picture's top towards +Y. `size` is the length of the picture's longest side in world units, and `center` is where its middle sits.

**Method.** Dual contouring keeps the corners of a hard-edged picture, a QR code or pixel art, square. Marching squares cuts each of those corners at 45 degrees, but follows a soft, blurred picture a little more smoothly. Both follow a smooth anti-aliased logo closely.

**Resolution** is how many samples the trace takes along the picture's longest side, 256 by default. A larger picture is averaged down to it first, which keeps the trace quick and the outlines smooth; a smaller one is traced at its own size, since samples between its texels would add nothing. Raise it for fine detail, lower it for a simpler outline. Pixel art keeps its corners exactly square only when traced at its own size.

**Tolerance** removes points that lie within that distance of a straight line through their neighbours, measured in samples so it does not change with `size`. It keeps a traced picture small: on a QR code it leaves only the corners. At 0 every point is kept.

A picture where nothing crosses the level is an error naming the range of values the channel holds, so you can set the level inside it.

**A texture made on the GPU is read back to the CPU.** In a browser the copy lands a tick or more later, and the nodes below this one wait for it. Changing only this node's params reuses the copy already made.

Tracing the Outline of a Leaf

geo/TextureTrace

Modeling