PlotlyJS doesn't implement orthographic projection option

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1

PlotlyJS has an option for orthographic projection rather than the default “perspective” projection. It is described in the docs here:

https://docs.juliaplots.org/stable/gallery/plotlyjs/generated/plotlyjs-ref060/

The orthographic example is actually using perspective.

The options work as intended with GR.

Code to reproduce (based on the example in the docs):

x = [[-1, 1], [-1, -1], [-1, 1], [1, 1], [1, 1], [-1, -1], [-1, -1], [1, 1], [-1, 1], [-1, -1], [-1, 1], [1, 1]]
y = [[1, 1], [-1, 1], [-1, -1], [-1, 1], [1, 1], [1, 1], [-1, -1], [-1, -1], [1, 1], [-1, 1], [-1, -1], [-1, 1]]
z = [[1, 1], [1, 1], [1, 1], [1, 1], [-1, 1], [-1, 1], [-1, 1], [-1, 1], [-1, -1], [-1, -1], [-1, -1], [-1, -1]]
kw = (aspect_ratio = :equal, label = :none, xlabel = "x", ylabel = "y", zlabel = "z", xlims = (-1.1, 1.1), ylims = (-1.1, 1.1), zlims = (-1.1, 1.1))

plotlyjs()

plot(plot(x, y, z; proj_type = :ortho, title = "PlotlyJS incorrect ortho", camera = (45, round(atand(1 / √2); digits = 3)), kw...),
     plot(x, y, z; proj_type = :persp, title = "PlotlyJS perspective", camera = (45, round(atand(1 / √2); digits = 3)), kw...))

gr()

plot(plot(x, y, z; proj_type = :ortho, title = "GR correct orthographic", camera = (45, round(atand(1 / √2); digits = 3)), kw...),
     plot(x, y, z; proj_type = :persp, title = "GR perspective", camera = (45, round(atand(1 / √2); digits = 3)), kw...))

(Am trying to figure out how to add graphics files…)

In the absence of graphics, the orthogonal projection of a cube at this angle should yield a regular hexagon, whereas perspective projection yields a hexagon that is appropriately distorted. PlotlyJS produces similar irregular hexagons for both cases, whereas GR does it right.

2

The GR docs and the PlotlyJS docs on the issue show the problem clearly

https://docs.juliaplots.org/stable/gallery/gr/generated/gr-ref060/#gr_ref060

vs

https://docs.juliaplots.org/stable/gallery/plotlyjs/generated/plotlyjs-ref060/

3

Using direct PlotlyJS, not via Plots, the two projections are distinct:
perspective
orthographic

2 Likes
4

OK, that helps localise the problem. Thanks!

Could you please show how to do that? I can plot using PlotlyJS without Plots, but I can’t figure out how to pass the projection parameter.

5

Set in Layout, scene_camera_projection_type="othographic"

6

Thanks,

I can’t get that to work exactly in that form, but using it as a starting point I arrived at this snippet which works, and generates an orthographic projection (which from this angle reduces to a 2-D X-Y view):

using PlotlyJS

rw() = cumsum(randn(400))
trace1 = scatter3d(;x=rw(),y=rw(), z=rw(), mode="lines")
layout=Layout(scene=attr(camera=attr(eye=attr(x=0.0, y=0.0, z=10.0),
                                     projection=attr(type="orthographic"))))
plot([trace1], layout)

pjstest
pjstest700×500 7.13 KB

This is a solution for me, but the problem remains that the example in the docs at 3D projection · Plots doesn’t work as advertised. Who should I tell?

7

What I posted is a path in a nested Dict interpreted as a tree with the root, scene. But finally you realized how to write it to have effect.
You may open an issue on the PlotlyJS.jl.repo or better, a PR to improve the docs related to projection type.