plane
A plane in space, drawn as its exact intersection with the box. plane(z: 4x + 2y - 3) is a height over the floor; plane(equation: x + 2y + 3z = 6) is any plane, a vertical slicing plane x = c among them. Either must be linear in x, y and z — a product or a power of them is refused — though a parameter may be a coefficient. A plane cuts every surface it passes through exactly, so a tangent plane meets its surface cleanly. Space only (graph:xyz).
plane

#Attributes
zThe height over the floor, linear in x and y:
4x + 2y - 3.plane-heightCan be written as shorthand:
plane:valueequationAny plane as an equation in x, y and z:
x + 2y + 3z = 6, x = c.plane-equationAlso written:
eqmeshRule the plane into a hairline grid.
Default
truecolourIts colour — green when not given. Faces are shaded in steps of the hue by how squarely they face a light fixed to the camera.
bluelight-bluedark-blueredlight-reddark-redorangelight-orangedark-orangeyellowlight-yellowdark-yellowteallight-tealdark-tealgreenlight-greendark-greenpinklight-pinkdark-pinkpurplelight-purpledark-purplegreylight-greydark-greyneutralhex(…)rgb(…)colorDefault
greenopacityHow solid it is, 0 to 1.
Default
0.45labelWords drawn beside it, over everything.
hiddenDeclared but not drawn — animatable, so
hidden: true !cue.to{false}(at: 2) is its reveal.Default
falselockA reader may not edit it.
Also written:
lockedDefault
falselayerAccepted for parity with the flat marks; in space the paint order is depth.
#Examples


graph:xyz{
surface(expression: 2 * x^2 + y^2)
plane(z: 4x + 2y - 3)
point(x: 1; y: 1; z: 3; label: $P$)
}(
x domain: [-2, 2]
y domain: [-2, 2]
z domain: [0, 12]
view: (35, 25)
)

graph:xyz{
plane(equation: x + 2y + 3z = 6)
plane(equation: x = 1; colour: orange)
}(
x domain: [-3, 3]
y domain: [-3, 3]
z domain: [-3, 3]
)