projection: Add flatten Option to Ortho

Author: johannes-wolf

CHANGES.md

@@ -27,6 +27,8 @@
 - Fixed a bug with cetz creating invalid stroke objects for `stroke: none` (#1059).
 - Increased the rounding digits from 8 to 10, fixing some rounding bugs
   with `ortho`.
+- Added a `flatten: (bool)` argument to `ortho`, that allows setting all z
+  components to zero.
 
 # 0.4.2
 - The `tree` element now has a `anchor:` argument to position the tree (#929)

gallery/paciolis.png

@@ -7,7 +7,7 @@
   import draw: *
   let phi = (1 + calc.sqrt(5)) / 2
 
-  ortho({
+  ortho(flatten: true, {
     hide({
       line(
         (-phi, -1, 0), (-phi, 1, 0), (phi, 1, 0), (phi, -1, 0), close: true, name: "xy",
@@ -33,11 +33,11 @@
     line("a.0", (0, -phi, 1), "b.2")
 
     anchor("A", (0, phi, 1))
-    content("A", [$A$], anchor: "north", padding: .1)
+    content("A", [$A$], anchor: "south", padding: .1)
     anchor("B", (-1, 0, phi))
-    content("B", [$B$], anchor: "south", padding: .1)
+    content("B", [$B$], anchor: "east", padding: .1)
     anchor("C", (1, 0, phi))
-    content("C", [$C$], anchor: "south", padding: .1)
+    content("C", [$C$], anchor: "north", padding: .1)
     line("A", "B", stroke: (dash: "dashed"))
     line("A", "C", stroke: (dash: "dashed"))
   })

gallery/paciolis.typ

@@ -246,12 +246,14 @@
 /// - cull-face (none,str): Enable back-face culling if set to `"cw"` for clockwise
 ///   or `"ccw"` for counter-clockwise. Polygons of the specified order will not get drawn.
 /// - reset-transform (bool): Ignore the current transformation matrix
+/// - flatten (bool): Set all z-components to 0.
 /// - body (element): Elements to draw
-#let ortho(x: 35.264deg, y: 45deg, z: 0deg, sorted: true, cull-face: none, reset-transform: false, body) = scope(ctx => {
+#let ortho(x: 35.264deg, y: 45deg, z: 0deg, sorted: true, cull-face: none, reset-transform: false, flatten: false, body) = scope(ctx => {
   _projection(body, ortho-matrix(x, y, z), ortho-projection-matrix,
     sorted: sorted,
     cull-face: cull-face,
-    reset-transform: reset-transform)
+    reset-transform: reset-transform,
+    flatten: flatten)
 })
 
 /// Draw elements on the xy-plane with optional z offset.