[geom] Render a mesh (or similar) to SVG

[timothypratley]

Hi! 👋

My goal is to define a basic shape in 3D coords, and turn it into an SVG from an isometric perspective. I'm hoping the result will be something like:
[:polygon {:points ...}]
That is to say, I want to define a simple 3D scene and convert it to 2D SVG shapes.

I think I've overcomplicated things but this is what I tried (copying from examples):

(ns my-ns
  (:require
            [thi.ng.geom.core :as g]
            [thi.ng.geom.matrix :as mat]
            [thi.ng.geom.svg.core :as svg]
            [thi.ng.geom.svg.adapter :as adapt]
            [thi.ng.geom.quad :as q]
            [thi.ng.geom.svg.renderer :as render]
            [thi.ng.geom.svg.shaders :as shader]
            [thi.ng.math.core :as m]))

(def width  640)
(def height 480)
(def model  (-> (mat/matrix44) (g/rotate-x m/HALF_PI) (g/rotate-z m/SIXTH_PI)))
(def view   (apply mat/look-at (mat/look-at-vectors 0 0 -2 0 0 0)))
(def proj   (mat/perspective 60 (/ width height) 0.1 2))
(def mvp    (->> model (m/* view) (m/* proj)))
(def col-tx (g/rotate-x (mat/matrix44) (- m/HALF_PI)))
(def mesh (g/as-mesh (q/quad3 10)))
(def screen (mat/viewport-matrix width height))
(def shader
  (shader/shader
    {:fill     (shader/phong
                 {:model     model
                  :view      view
                  :light-pos [0 -2 1]
                  :light-col [1 1 1]
                  :diffuse   (shader/normal-rgb col-tx)
                  :ambient   [0.1 0.1 0.2]
                  :specular  1.0
                  :shininess 6.0})
     :uniforms {:stroke "black" :stroke-width 0.25}
     :flags    {:solid true}}))

(render/mesh mesh mvp screen nil)
;;=>  [:g {:stroke "black", :stroke-width 0.25} ()]

It made a group, which is great, but the contents are empty.
Probably the mesh here is the issue?
Maybe it is missing a material or something to make it visible?

I'm not attached to using a shader, it was a required argument (fails when nil), so I copied it from an example.

Any pointers would help, thank you!

[timothypratley]

Messing around a bit more...

(defn render-mesh
  [mesh mvp screen]
  (let [faces (render/project-faces mvp screen (map #(g/vertices % mesh) (g/faces mesh false)))
        faces (->> faces
                   (render/z-map-faces)
                   (render/z-sort-faces first))]
    (map (fn [face] (svg/polygon (second face))) faces)))
(render-mesh mesh mvp screen)
;;=> ([:polygon {:points "0.00,0.00 10.00,0.00 10.00,10.00 0.00,10.00"}])

Which I think sets me on the path to victory. 🤔

[timothypratley]

Also just curious if there is a way to go from data to objects:

{:vertices #{[0.0 10.0 0.0]
             [10.0 0.0 0.0]
             [10.0 10.0 0.0]
             [0.0 0.0 0.0]},
 :faces #{[0.0 0.0 0.0] [10.0 0.0 0.0] [10.0 10.0 0.0] [0.0 10.0 0.0]]}}

or similar and create a #thi.ng.geom.types.BasicMesh

[timothypratley]

thinking about it a bit more, a tree walk would do it conveniently.
edit: oh right there are tagged literals for everything, so it is data