Unable to setobject! in atframe

[dmillard]

MWE:

using MeshCat    
using GeometryTypes    
                                                                                                               
vis = Visualizer()    
open(vis)    
                                                                                                               
function test!(vis)                                                                                                               
  anim = Animation()    
  for i in 1:10                                                                                                                                         
    atframe(anim, i) do    
      marker = Sphere(Point3(0., 0., 0.), i/10)    
      setobject!(vis, marker)    
    end    
  end    
  setanimation!(vis, anim)    
end    
                                                                                                               
test!(vis)

Output:

ERROR: LoadError: type DataType has no field body
Stacktrace:
 [1] getproperty at ./Base.jl:15 [inlined]
 [2] call at /home/drm/.julia/packages/Cassette/YCOeN/src/context.jl:447 [inlined]
 [3] fallback at /home/drm/.julia/packages/Cassette/YCOeN/src/context.jl:445 [inlined]
 [4] overdub at /home/drm/.julia/packages/Cassette/YCOeN/src/context.jl:271 [inlined]
 [5] typename at ./essentials.jl:294 [inlined]
 [6] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(Base.typename), ::Type{ColorTypes.RGB}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [7] typename at ./essentials.jl:294 [inlined]
 [8] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(Base.typename), ::Type{ColorTypes.RGB}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [9] basetype at /home/drm/.julia/packages/ColorTypes/TvB32/src/traits.jl:156 [inlined]
 [10] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(ColorTypes.basetype), ::Type{ColorTypes.RGB}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [11] base_colorant_type at /home/drm/.julia/packages/ColorTypes/TvB32/src/traits.jl:157 [inlined]
 [12] eltypes_supported at /home/drm/.julia/packages/ColorTypes/TvB32/src/traits.jl:97 [inlined]
 [13] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(ColorTypes.eltypes_supported), ::Type{ColorTypes.RGB}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [14] issupported at /home/drm/.julia/packages/ColorTypes/TvB32/src/traits.jl:102 [inlined]
 [15] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(ColorTypes.issupported), ::Type{ColorTypes.RGB}, ::Type{Float32}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [16] pick_eltype at /home/drm/.julia/packages/ColorTypes/TvB32/src/traits.jl:296 [inlined]
 [17] ccolor at /home/drm/.julia/packages/ColorTypes/TvB32/src/traits.jl:279 [inlined]
 [18] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(ColorTypes.ccolor), ::Type{ColorTypes.RGB}, ::Type{ColorTypes.RGBA{Float32}}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [19] convert at /home/drm/.julia/packages/ColorTypes/TvB32/src/conversions.jl:7 [inlined]
 [20] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(convert), ::Type{ColorTypes.RGB}, ::ColorTypes.RGBA{Float32}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [21] lower at /home/drm/.julia/packages/MeshCat/GMobF/src/lowering.jl:215 [inlined]
 [22] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(MeshCat.lower), ::MeshCat.GenericMaterial) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [23] lower at /home/drm/.julia/packages/MeshCat/GMobF/src/lowering.jl:21 [inlined]
 [24] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(MeshCat.lower), ::Object{HyperSphere{3,Float64},MeshCat.GenericMaterial}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [25] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(MeshCat.lower), ::MeshCat.SetObject{Object{HyperSphere{3,Float64},MeshCat.GenericMaterial}}) at /home/drm/.julia/packages/MeshCat/GMobF/src/lowering.jl:265
 [26] send at /home/drm/.julia/packages/MeshCat/GMobF/src/visualizer.jl:110 [inlined]
 [27] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::typeof(MeshCat.send), ::MeshCat.CoreVisualizer, ::MeshCat.SetObject{Object{HyperSphere{3,Float64},MeshCat.GenericMaterial}}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [28] setobject! at /home/drm/.julia/packages/MeshCat/GMobF/src/visualizer.jl:164 [inlined]
 [29] setobject! at /home/drm/.julia/packages/MeshCat/GMobF/src/abstract_visualizer.jl:12 [inlined]
 [30] #3 at /tmp/MWE.jl:12 [inlined]
 [31] overdub(::Cassette.Context{nametype(AnimationCtx),Tuple{Animation,Int64},Nothing,getfield(Cassette, Symbol("##PassType#373")),Nothing,Nothing}, ::getfield(Main, Symbol("##3#4")){Visualizer,Int64}) at /home/drm/.julia/packages/Cassette/YCOeN/src/overdub.jl:0
 [32] atframe at /home/drm/.julia/packages/MeshCat/GMobF/src/atframe.jl:58 [inlined]
 [33] test!(::Visualizer) at /tmp/MWE.jl:10
 [34] top-level scope at /tmp/MWE.jl:18
 [35] include at ./boot.jl:328 [inlined]
 [36] include_relative(::Module, ::String) at ./loading.jl:1094
 [37] include(::Module, ::String) at ./Base.jl:31
 [38] exec_options(::Base.JLOptions) at ./client.jl:295
 [39] _start() at ./client.jl:464
in expression starting at /tmp/MWE.jl:18

[dmillard]

Really, I'm not sure that this is even a supported use-case, but I'm trying to update a LineSegment object once per frame, and can't think of a better way to do it than setobject! inside the atframe.

Thanks for meshcat, it's a pleasure to use.

[rdeits]

Hey, sorry for the late reply. Yes, you're right this doesn't work, but we should give a more helpful error message.

The problem is that, as far as I know, there's no way to cause Three.js to spawn an object as part of an animation. Instead, I think you should be able to get this to work by adding the object ahead of time and then setting the visible property at the relevant frame.

[dmillard]

Thanks for the feedback! For my use case, that seems like quite a lot of hidden objects sitting around, but I'll keep it in mind.

[rdeits]

The animation demo notebook now more explicitly talks about using setvisible! to create objects that appear to pop in and out of existence in an animation: https://github.com/rdeits/MeshCat.jl/blob/master/notebooks/animation.ipynb#Making-Objects-Appear-and-Disappear

[ga72kud]

@rdeits is this workaround also suitable for large datasets like visualizing huge LIDAR datasets? I come to the same error message with "> type DataType has no field body" and want to test it by changing my code with setvisible!...