# Completely vertical polygons not showing with GLMakie poly!()

**URL:** https://discourse.julialang.org/t/completely-vertical-polygons-not-showing-with-glmakie-poly/133350
**Category:** General Usage
**Tags:** plotting, makie
**Created:** [October 21, 2025, 11:21pm UTC](https://discourse.julialang.org/t/completely-vertical-polygons-not-showing-with-glmakie-poly/133350 "2025-10-21T23:21:52Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![Michael\_Wang](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/michael_wang/32/8535_2.png) [@Michael\_Wang](https://discourse.julialang.org/u/Michael_Wang)
#### Post date: [October 21, 2025, 11:21pm UTC](https://discourse.julialang.org/t/completely-vertical-polygons-not-showing-with-glmakie-poly/133350/1 "2025-10-21T23:21:52Z")

</div>

I’m trying to plot some polygons in 3D space with GLMakie and noticed that polygons that are complete vertical do not show up. Below is a script that plots a set of triangles where I drag one vertex along a line. Notice that the y = 0 triangle does not show up.

```julia-auto
using GLMakie

lscene = LScene(fig[1, 1])
for y = -10 : 2 : 10
    poly!(Point3f[[0.0, 0.0, 5.0], [10.0, 0.0, 5.0], [10.0, y, 0.0]], shading = true)
end

wait(display(fig))

```

 ![image](https://global.discourse-cdn.com/julialang/original/3X/4/9/49188902b8df400100a1057e6a5665149b2c716e.png)

If instead I add a tiny offset to the y values, all the triangles are displayed.

```julia-auto
using GLMakie

lscene = LScene(fig[1, 1])
for y = -10 : 2 : 10
    poly!(Point3f[[0.0, 0.0, 5.0], [10.0, 0.0, 5.0], [10.0, y+0.00001, 0.0]], shading = true)
end

wait(display(fig))

```

 ![image](https://global.discourse-cdn.com/julialang/original/3X/7/8/7804b87d2f28cbf06ff02284bb699c775c9a235d.png)

Is this a bug or am I missing something crucial?

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<div class="post-metadata">

### Author: ![asinghvi17](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/asinghvi17/32/8272_2.png) [@asinghvi17](https://discourse.julialang.org/u/asinghvi17)
#### Post date: [October 22, 2025, 1:18am UTC](https://discourse.julialang.org/t/completely-vertical-polygons-not-showing-with-glmakie-poly/133350/2 "2025-10-22T01:18:27Z")

</div>

It’s a bug in how we mesh the polygons for display since it currently just takes the x and y coordinates, and ignores the z coordinate.

I have a way to make the triangulation live in the plane of the polygon in 3D (by finding the plane of best fit to the set of vertices of the polygon) [here](https://github.com/MakieOrg/GeoMakie.jl/blob/master/src/triangulation3d.jl), which could be moved to Makie instead…what do you think @sdanisch?