# thi-ng/geom

Switch branches/tags
Nothing to show
Fetching contributors…
Cannot retrieve contributors at this time
311 lines (270 sloc) 10.5 KB

# thi.ng.geom.types.utils.ptf

## Parallel Transport Frames

```(defn compute-tangents
[points]
(let [t (mapv (fn [[p q]] (g/normalize (g/- q p))) (d/successive-nth 2 points))]
(conj t (peek t))))

(defn compute-frame
[tangents norms bnorms i]
(let [ii (dec i)
p  (tangents ii)
q  (tangents i)
a  (g/cross p q)
n  (if-not (m/delta= 0.0 (g/mag-squared a))
(let [theta (Math/acos (m/clamp-normalized (g/dot p q)))]
(g/transform-vector (g/rotate-around-axis M44 (g/normalize a) theta) (norms ii)))
(norms ii))]
[n (g/cross q n)]))

(defn compute-first-frame
[t]
(let [t' (g/abs t)
i  (if (< (t' 0) (t' 1)) 0 1)
i  (if (< (t' 2) (t' i)) 2 i)
n  (g/cross t (g/normalize (g/cross t (assoc V3 i 1.0))))]
[n (g/cross t n)]))

(defn compute-frames
[points]
(let [tangents (compute-tangents points)
[n b]    (compute-first-frame (first tangents))
num      (count tangents)]
(loop [norms [n], bnorms [b], i 1]
(if (< i num)
(let [[n b] (compute-frame tangents norms bnorms i)]
(recur (conj norms n) (conj bnorms b) (inc i)))
[points tangents norms bnorms]))))

(defn align-frames
[[points tangents norms bnorms]]
(let [num   (count tangents)
a     (first norms)
b     (peek norms)
theta (-> (g/dot a b) (m/clamp-normalized) (Math/acos) (/ (dec num)))
theta (if (> (g/dot (first tangents) (g/cross a b)) 0.0) (- theta) theta)]
(loop [norms norms, bnorms bnorms, i 1]
(if (< i num)
(let [t (tangents i)
n (-> M44
(g/rotate-around-axis t (* theta i))
(g/transform-vector (norms i)))
b (g/cross t n)]
(recur (assoc norms i n) (assoc bnorms i b) (inc i)))
[points tangents norms bnorms]))))

(defn sweep-point
"Takes a path point, a PTF normal & binormal and a profile point.
Returns profile point projected on path (point)."
[p n b [qx qy]]
(vec3
(mm/madd qx (n 0) qy (b 0) (p 0))
(mm/madd qx (n 1) qy (b 1) (p 1))
(mm/madd qx (n 2) qy (b 2) (p 2))))

(defn sweep-profile
[profile [points _ norms bnorms]]
(let [frames (map vector points norms bnorms)
tx     (fn [[p n b]] (mapv #(sweep-point p n b %) profile))
frame0 (tx (first frames))]
(->> (next frames) ;; TODO transducer
(reduce
(fn [[faces prev] frame]
(let [curr  (tx frame)
curr  (conj curr (first curr))
faces (->> (mapcat
(fn [a b] [(vector (a 0) (a 1) (b 1) (b 0))])
(d/successive-nth 2 prev)
(d/successive-nth 2 curr))
(concat faces))]
[faces curr]))
[nil (conj frame0 (first frame0))])
(first))))

(defn sweep-mesh
[points profile & [{:keys [mesh align?]}]]
(let [frames (compute-frames points)
frames (if align? (align-frames frames) frames)]
(->> frames
(sweep-profile profile)
(g/into (or mesh (bm/basic-mesh))))))

(defn sweep-strand
[[p _ n b] r theta delta profile]
(-> (mapv
#(->> (vec2 r (mm/madd % delta theta))
(g/as-cartesian)
(sweep-point (p %) (n %) (b %)))
(range (count p)))
(sweep-mesh profile {:align? true})))

(defn sweep-strands
[base r strands twists profile]
(let [delta (/ (* twists TWO_PI) (dec (count (first base))))]
(->> (m/norm-range strands)
(butlast)
(#?(:clj pmap :cljs map) #(sweep-strand base r (* % TWO_PI) delta profile)))))

(defn sweep-strand-mesh
[base r strands twists profile & [{:as opts}]]
(->> (sweep-strands base r strands twists profile)
(reduce g/into (or (:mesh opts) (bm/basic-mesh)))))```

## Luxor torus knot examples

The following brief examples demonstrate usage of the `sweep-mesh` and `sweep-strand-mesh` functions in combination with thi.ng/luxor’s test scene setup. The first example computes a Cinquefoil knot (a (5,2)-torus knot) and sweeps a circle along the path using PTF. The second demo also uses the same knot as basis, but instead of sweeping it directly, first computes N strands, each rotating around the path at given radius and each strand swept as mesh individually (then combined into a single mesh using `g/into`). Both examples are tangled into the `/babel/examples` directory, but will only work in a REPL which has both the `geom` and `luxor` libs on its classpath.

```(ns ptf-knot
(:require
[thi.ng.geom.core :as g]
[thi.ng.geom.core.vector :as v]
[thi.ng.geom.aabb :as a]
[thi.ng.geom.circle :as c]
[thi.ng.geom.types.utils.ptf :as ptf]
[thi.ng.math.core :as m :refer [THIRD_PI TWO_PI]]
[thi.ng.luxor.scenes :as scene]
[thi.ng.luxor.io :as lio]))

(defn cinquefoil
[t]
(let [t  (* t m/TWO_PI)
pt (* 2.0 t)
qt (* 5.0 t)
qc (+ 3.0 (Math/cos qt))]
(v/vec3 (* qc (Math/cos pt)) (* qc (Math/sin pt)) (Math/sin qt))))

(-> (scene/base-scene {:width 640 :height 360})
(ptf/sweep-mesh
(mapv cinquefoil (m/norm-range 400))
(g/vertices (c/circle 0.5) 20)
{:align? true})
{:id :knot :bounds (a/aabb 1.5) :target [0 0.5 -2] :rx (- m/THIRD_PI)})
(lio/serialize-scene "ptf-knot" false)
(lio/export-scene)
(dorun))```

Some example renders to illustrate the `weave-mesh` approach/function with different parameters:

```(ns ptf-knot2
(:require
[thi.ng.geom.core :as g]
[thi.ng.geom.core.vector :as v]
[thi.ng.geom.aabb :as a]
[thi.ng.geom.circle :as c]
[thi.ng.geom.types.utils.ptf :as ptf]
[thi.ng.math.core :as m]
[thi.ng.luxor.scenes :as scene]
[thi.ng.luxor.io :as lio]))

(defn cinquefoil
[t]
(let [t  (* t m/TWO_PI)
pt (* 2.0 t)
qt (* 5.0 t)
qc (+ 3.0 (Math/cos qt))]
(v/vec3 (* qc (Math/cos pt)) (* qc (Math/sin pt)) (Math/sin qt))))

(def knot
(-> (mapv cinquefoil (m/norm-range 400))
(ptf/compute-frames)
(ptf/align-frames)))

(-> (scene/base-scene {:width 640 :height 360})
(ptf/sweep-strand-mesh knot 0.5 10 7 (g/vertices (c/circle 0.1) 20))
;;(ptf/sweep-strand-mesh knot 0.8 6 12 (g/vertices (c/circle 0.1) 20))
{:id :knot-weave :bounds (a/aabb 1.5) :target [0 0.5 -2] :rx (- m/THIRD_PI)})
(lio/serialize-scene "ptf-knot-weave" false)
(lio/export-scene)
(dorun))```

```(ns ptf-knot3
(:require
[thi.ng.geom.core :as g]
[thi.ng.geom.core.vector :as v]
[thi.ng.geom.circle :as c]
[thi.ng.geom.types.utils.ptf :as ptf]
[thi.ng.math.core :as m]
[thi.ng.luxor.core :as lux]
[thi.ng.luxor.scenes :as scene]
[thi.ng.luxor.io :as lio]
[thi.ng.color.core :as col]))

(defn cinquefoil
[t]
(let [t  (* t m/TWO_PI)
pt (* 2.0 t)
qt (* 5.0 t)
qc (+ 3.0 (Math/cos qt))]
(v/vec3 (* qc (Math/cos pt)) (* qc (Math/sin pt)) (Math/sin qt))))

[scene meshes opts]
(let [hue (/ 1.0 (count meshes))]
(reduce
(fn [scene [i mesh]]
(let [mat (str "matte-hue-" i)]
(-> scene
(lux/material-matte mat {:diffuse (col/hsva (* i hue) 1.0 0.9)})
(scene/add-mesh mesh (assoc opts :material mat :id (str "strand-" i))))))
scene (zipmap (range) meshes))))

(def knot
(-> (mapv cinquefoil (m/norm-range 400))
(ptf/compute-frames)
(ptf/align-frames)))

(-> (scene/base-scene {:width 640 :height 360})
(ptf/sweep-strands knot 0.5 10 7 (g/vertices (c/circle 0.1) 20))
{:tx {:translate [0 0.5 -2] :scale 0.175 :rx -65}})
(lio/serialize-scene "ptf-knot-weave-spectrum" false)
(lio/export-scene)
(dorun))```

```(ns ptf-spline
(:require
[thi.ng.geom.core :as g]
[thi.ng.geom.core.vector :as v]
[thi.ng.geom.aabb :as a]
[thi.ng.geom.bezier :as b]
[thi.ng.geom.circle :as c]
[thi.ng.geom.types.utils.ptf :as ptf]
[thi.ng.math.core :as m]
[thi.ng.luxor.core :as lux]
[thi.ng.luxor.scenes :as scene]
[thi.ng.luxor.io :as lio]))

(-> (scene/base-scene {:width 640 :height 360})
(assoc-in [:camera "perspective" :focaldistance 1] 1.4)
(ptf/sweep-mesh
(-> (for [i (range 100)] (v/randvec3))
(b/auto-spline3)
(g/vertices))
(g/vertices (c/circle 0.025) 10))
{:id :spline :bounds (a/aabb 1.25) :target [0 0.625 -1.75] :rx (- m/THIRD_PI)})
(lio/serialize-scene "ptf-spline" false)
(lio/export-scene)
(dorun))```

## Namespace declaration

```(ns thi.ng.geom.types.utils.ptf
#?(:cljs (:require-macros [thi.ng.math.macros :as mm]))
(:require
[thi.ng.geom.core :as g]
[thi.ng.geom.core.vector :refer [vec2 vec3 V3]]
[thi.ng.geom.core.matrix :refer [matrix44 M44]]
[thi.ng.geom.basicmesh :as bm]
[thi.ng.dstruct.core :as d]
[thi.ng.math.core :as m :refer [*eps* TWO_PI]]
#?(:clj [thi.ng.math.macros :as mm])))

<<ptf>>```