add path tracing and loop rendering option to animations

docs/src/examples/pendulum.md

@@ -220,14 +220,15 @@ end
 model = complete(model)
 ssys = structural_simplify(IRSystem(model))
 
-prob = ODEProblem(ssys, [model.shoulder_joint.phi => 0.0, model.elbow_joint.phi => 0.1], (0, 12))
+prob = ODEProblem(ssys, [model.shoulder_joint.phi => 0.0, model.elbow_joint.phi => 0.1], (0, 10))
 sol = solve(prob, Rodas4())
 plot(sol, layout=4)
 ```
 
+In the animation below, we visualize the path that the origin of the pendulum tip traces by providing the tip frame in a vector of frames passed to `traces`
 ```@example pendulum
 import GLMakie
-Multibody.render(model, sol, filename = "furuta.gif")
+Multibody.render(model, sol, filename = "furuta.gif", traces=[model.tip.frame_a])
 nothing # hide
 ```
 ![furuta](furuta.gif)

docs/src/rendering.md

@@ -24,6 +24,10 @@ Many components allows the user to select with which color it is rendered. This
 ## Rendering the world frame
 The display of the world frame can be turned off by setting `world.render => false` in the variable map.
 
+## Tracing the path of a frame in 3D visualizations
+The path that a frame traces out during simulation can be visualized by passing a vector of frames to the `render` function using the `traces` keyword, e.g., `render(..., traces=[frame1, frame2])`.
+See the Furuta-pendulum demonstration [Going 3D](@ref) for an example of this.
+
 
 ## Rendering API
 

ext/Render.jl

@@ -1,11 +1,11 @@
 module Render
 using Makie
 using Multibody
-import Multibody: render, render!, encode, decode, get_rot, get_trans, get_frame
+import Multibody: render, render!, loop_render, encode, decode, get_rot, get_trans, get_frame
 using Rotations
 using LinearAlgebra
 using ModelingToolkit
-export render
+export render, loop_render
 using MeshIO, FileIO
 using StaticArrays
 
@@ -129,6 +129,9 @@ function render(model, sol,
  up = Vec3f(0,1,0),
  show_axis = false,
  timescale = 1.0,
+ traces = nothing,
+ display = false,
+ loop = 1,
  kwargs...
  )
  scene, fig = default_scene(x,y,z; lookat,up,show_axis)
@@ -139,30 +142,85 @@ function render(model, sol,
  t = Observable(timevec[1])
 
  recursive_render!(scene, complete(model), sol, t)
- fn = record(fig, filename, timevec; framerate) do time
- t[] = time/timescale
+
+ if traces !== nothing
+ tvec = range(sol.t[1], stop=sol.t[end], length=500)
+ for frame in traces
+ (frame.metadata !== nothing && get(frame.metadata, :frame, false)) || error("Only frames can be traced in animations.")
+ points = get_trans(sol, frame, tvec) |> Matrix
+ Makie.lines!(scene, points)
+ end
+ end
+ if loop > 1
+ timevec = repeat(timevec, loop)
+ end
+ if display
+ Base.display(fig)
+ sleep(2)
+ fnt = @async begin
+ record(fig, filename, timevec; framerate) do time
+ if time == timevec[1]
+ Base.display(fig)
+ end
+ t[] = time/timescale
+ sleep(max(0, 1/framerate))
+ end
+ end
+ fn = fetch(fnt)
+ else
+ fn = record(fig, filename, timevec; framerate) do time
+ t[] = time/timescale
+ end
  end
+
  fn, scene, fig
 end
 
 function render(model, sol, time::Real;
+ traces = nothing,
+ x = 2,
+ y = 0.5,
+ z = 2,
  kwargs...,
  )
 
  # fig = Figure()
  # scene = LScene(fig[1, 1]).scene
  # cam3d!(scene)
- scene, fig = default_scene(0,0,10; kwargs...)
+ scene, fig = default_scene(x,y,z; kwargs...)
  # mesh!(scene, Rect3f(Vec3f(-5, -3.6, -5), Vec3f(10, 0.1, 10)), color=:gray) # Floor
 
  steps = range(sol.t[1], sol.t[end], length=3000)
 
  t = Slider(fig[2, 1], range = steps, startvalue = time).value
-
  recursive_render!(scene, complete(model), sol, t)
+
+ if traces !== nothing
+ tvec = range(sol.t[1], stop=sol.t[end], length=500)
+ for frame in traces
+ (frame.metadata !== nothing && get(frame.metadata, :frame, false)) || error("Only frames can be traced in animations.")
+ points = get_trans(sol, frame, tvec) |> Matrix
+ Makie.lines!(scene, points)
+ end
+ end
  fig, t
 end
 
+function Multibody.loop_render(model, sol; timescale = 1.0, framerate = 30, max_loop = 5, kwargs...)
+ fig, t = render(model, sol, sol.t[1]; kwargs...)
+ sleeptime = 1/framerate
+ timevec = range(sol.t[1], sol.t[end]*timescale, step=sleeptime)
+ display(fig)
+ @async begin
+ for i = 1:max_loop
+ for ti in timevec
+ execution_time = @elapsed t[] = ti
+ sleep(max(0, sleeptime - execution_time))
+ end
+ end
+ end
+end
+
 """
 Internal function: Recursively render all subsystem components of a multibody system. If a particular component returns `true` from its `render!` method, indicating that the component performaed rendering, the recursion stops.
 """

src/Multibody.jl

@@ -11,8 +11,8 @@ export Rotational, Translational
 export render, render!
 
 """
- scene, time = render(model, sol, t::Real; framerate = 30)
- path = render(model, sol, timevec = range(sol.t[1], sol.t[end], step = 1 / framerate); framerate = 30, timescale=1)
+ scene, time = render(model, sol, t::Real; framerate = 30, traces = [])
+ path = render(model, sol, timevec = range(sol.t[1], sol.t[end], step = 1 / framerate); framerate = 30, timescale=1, display=false, loop=1)
 
 Create a 3D animation of a multibody system
 
@@ -23,7 +23,9 @@ Create a 3D animation of a multibody system
 - `timevec`: If a vector of times is provided, an animation is created and the path to the file on disk is returned.
 - `framerate`: Number of frames per second.
 - `timescale`: Scaling of the time vector. This argument can be made to speed up animations (`timescale < 1`) or slow them down (`timescale > 1`). A value of `timescale = 2` will be 2x slower than real time.
+- `loop`: The animation will be looped this many times. Please note: looping the animation using this argument is only recommended when `display = true` for camera manipulation purposes. When the camera is not manipulated, looping the animation by other means is recommended to avoid an increase in the file size.
 - `filename` controls the name and the file type of the resulting animation
+- `traces`: An optional array of frames to show the trace of.
 
 # Camera control
 The following keyword arguments are available to control the camera pose:
@@ -32,9 +34,19 @@ The following keyword arguments are available to control the camera pose:
 - `z = 2`
 - `lookat = [0,0,0]`: a three-vector of coordinates indicating the point at which the camera looks.
 - `up = [0,1,0]`: A vector indicating the direction that is up.
+- `display`: if `true`, the figure will be displayed during the recording process and time will advance in real-time. This allows the user to manipulate the camera options using the mouse during the recording.
+
+See also [`loop_render`](@ref)
 """
 function render end
 
+"""
+ loop_render(model, sol; framerate = 30, timescale = 1, max_loop = 5, kwargs...)
+
+Similar to the method of [`render`](@ref) that produces an animation, but instead opens an interactive window where the time is automatically advanced in real time. This allows the user to manually manipulate the camera using the mouse is a live animation.
+"""
+function loop_render end
+
 """
  did_render::Bool = render!(scene, ::typeof(ComponentConstructor), sys, sol, t)
 

src/orientation.jl

@@ -381,9 +381,8 @@ end
 Extract the translational part of a frame from a solution at time `t`.
 See also [`get_rot`](@ref), [`get_frame`](@ref), [Orientations and directions](@ref) (docs section).
 """
-function get_trans(sol, frame, t)
- SVector{3}(sol(t, idxs = collect(frame.r_0)))
-end
+get_trans(sol, frame, t::Number) = SVector{3}(sol(t, idxs = collect(frame.r_0)))
+get_trans(sol, frame, t::AbstractArray) = sol(t, idxs = collect(frame.r_0))
 
 """
  T_W_F = get_frame(sol, frame, t)