Hi,
I am working on several 3D drawings and would like to control their position using azimuth and elevation. I studied the ortho function to create a custom version, but it relies on several non-exported functions.
So far, I have built a function without the ortho environment (see below). Am I on the right track? One feature I am still missing is the automatic sorting of drawables provided by ortho.
#let set-projection(azimuth:30deg, elevation:30deg) = {
import cetz.vector:*
(ctx => {
// save current translation
let pr = cetz.draw.ortho
let t1 = ctx.transform.at(0).at(3)
let t2 = ctx.transform.at(1).at(3)
let t3 = ctx.transform.at(2).at(3)
// get scale
let sx = len((ctx.transform.at(0).at(0), ctx.transform.at(1).at(0), ctx.transform.at(2).at(0)))
let sy = len((ctx.transform.at(0).at(1), ctx.transform.at(1).at(1), ctx.transform.at(2).at(1)))
let sz = len((ctx.transform.at(0).at(2), ctx.transform.at(1).at(2), ctx.transform.at(2).at(2)))
// orthographic projection matrix
let ortho-mat = (
(sx, 0, -0.01, 0),
(0, -sy, 0.01, 0),
(0, 0, 0, 0),
(0, 0, 0, 1),
)
let mat-1 = cetz.matrix.transform-rotate-x(-90deg) // rotate x -90deg to have z pointing up
let mat-2 = cetz.matrix.transform-rotate-z(-90deg - azimuth) // rotate z -90deg to have x pointing to the viewer then rotate by azimuth
let (l,m,n) = ( -calc.sin(azimuth), calc.cos(azimuth), 0) // new axis used for elevation
let (c, s) = (calc.cos(elevation), calc.sin(elevation))
let mat-elevation = ( ( l*l*(1-c) + c, l*m*(1-c) -n*s, l*n*(1-c) + m*s, 0 ),
( m*l*(1-c) + n*s, m*m*(1-c) + c, m*n*(1-c) - l*s, 0 ),
( n*l*(1-c) - m*s, n*m*(1-c) + l*s, n*n*(1-c) + c, 0 ),
(0,0,0,1) )
ctx.transform = cetz.matrix.mul-mat(ortho-mat, mat-1, mat-2, mat-elevation)
// restore translation
ctx.transform.at(0).at(3) = t1
ctx.transform.at(1).at(3) = t2
ctx.transform.at(2).at(3) = t3
return (ctx: ctx)
},)
}