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https://github.com/simon-lc/glvisualizer.jl

Robot visualization tools using OpenGL backend.
https://github.com/simon-lc/glvisualizer.jl

depth point-cloud visualization

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Robot visualization tools using OpenGL backend.

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# GLVisualizer.jl

Robot visualization tool using OpenGL backend. The API proposed in this package is heavily inspired from [MeshCat.jl](https://github.com/rdeits/MeshCat.jl). The reason for developing this package was to access depth information from a camera view. A tutorial on doing just this is provided below.



## Quick start

#### create and open a visualizer



```

resolution = (600, 400)

vis = GLVisualizer(resolution=resolution)

open(vis)

```

#### set a floor object

```

set_floor!(vis, color=RGBA(0.4, 0.4, 0.4, 0.2))

```

#### create two objects

```

object1 = HyperRectangle(Vec(0,0,0), Vec(0.2, 0.9, 1))

object2 = HyperRectangle(Vec(0,0,0), Vec(0.6, 0.2, 2.0))

```



#### add both objects to the scene, this defines a tree representation: root -> object1 -> object2. Moving the frame of object1 will move object2 accordingly.

```

setobject!(vis, :root, :object1, object1, color=RGBA(0,0,1,0.4))

setobject!(vis, :object1, :object2, object2, color=RGBA(1,0,0,0.4))

```



#### set the camera position, the point we are looking at and the upward direction of the camera.

```

eyeposition = [0,2,5.0]

lookat = [1,0,0.0]

up = [0,0,1.0]



set_camera!(vis;

		eyeposition=eyeposition,

		lookat=lookat,

		up=up,

		far=100.0,

		near=0.1,

		zoom=1.0,

		)

```



#### set the pose of both objects

```

settransform!(vis, :object1, [0,0,0.50], Makie.Quaternion(0,0,0,1.0))

settransform!(vis, :object2, [0,0,0.25], Makie.Quaternion(0,0,0,1.0))

```



#### compute depth for each pixel in the image generated by the camera

```

depth = depth_buffer(vis)

maximum(depth)

minimum(depth)

```



#### in-place version of the depth query, this still allocates memory though

```

depth = depth_buffer!(depth, vis)

maximum(depth)

minimum(depth)

```



#### convert depth pixels to 3D coordinates in the world frame and sotre them in wolrd_coordinates

```

p1 = Vector(range(200, step=32, length=10))

p2 = Vector(range(100, step=32, length=10))

n1 = length(p1)

n2 = length(p2)

world_coordinates = zeros(3, n1 * n2)

depthpixel_to_world!(world_coordinates, depth, p1, p2, vis)

```



#### create a pixel object to visualize where it is positioned in 3D space, then position all the pixels

```

pixel_object = HyperSphere(Point{3}(0,0,0.0), 0.05)

for i = 1:size(world_coordinates, 2)

	setobject!(vis, :root, Symbol(:pixel, i), pixel_object, color=RGBA(0.0,0.0,0.0,1.0))

	settransform!(vis, Symbol(:pixel, i), world_coordinates[:,i], Makie.Quaternion(0,0,0,1.0))

end

```



#### camera view from the front




#### camera view from the side




#### plot the depth image and visualize the pixels that have been extracted from it

```

linear_depth = (depth .- minimum(depth)) ./ (maximum(depth) - minimum(depth))

point_depth = deepcopy(linear_depth)

for i in p1

	for j in p2

		point_depth[i .+ (-4:4), j .+ (-4:4)] .= 1.0

	end

end

```



#### depth image

```

Plots.plot(Gray.(1 .- rotl90(linear_depth)))

```




#### depth image with pixel highlighted

```

Plots.plot(Gray.(1 .- rotl90(point_depth)))

```