Y Axis Gizmo randomly disappears at some angles

[nathanfranke]

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Bugsquad note: This issue has been confirmed several times already. No need to confirm it further.

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Godot version:
951ecc4

OS/device including version:
Linux Mint 19.3

Issue description:
Y Axis (Maybe others) randomly disappear

Godot.Y.Axis.Gizmo.randomly.disappears.TqutiJX70xE.webm

Steps to reproduce:

Use mouse wheel to orbit the viewport

Minimal reproduction project:
I just made an empty project and saw this

[Calinou]

Can you reproduce this in 3.2.1 as well?

[nathanfranke]

No but it seems to shift around 1 pixel instead so shouldn't matter

[Zylann]

I got lines disappearing too in 2D with draw_line(), with a particular drawing transform.
Repro:
Graphing_line_disappears.zip
The value I entered in _view_scale is frequently coming up when zoom is used in my app.
Should I make this a separate issue?

[aaronfranke]

This might not be a good solution, but maybe we should just force the 3D viewport to be an odd number of pixels wide? This could be done in the Node3D EditorPlugin so that this restriction doesn't exist for the other main screen plugins.

[nathanfranke]

@aaronfranke while still not the best solution we should either fix the draw line call for the axis or round that to one pixel

[Calinou]

If all else fails, we could draw two lines to ensure one of them is always visible, but this may make it too thick.

[nathanfranke]

Someone should do a bisect from 3.2 since there it seems to shift instead (unless this is some problem with vulkan)

[Thane5]

I always used to have this bug, but in v4.0.dev.calinou [7188cb6] it looks fine now.

[Kemeros]

Still present.
Windows 10
v4.0.dev.custom_build [dc81583]

[aaronfranke]

I have an ad-hoc fix here, but it's not perfect: #37995

[Kemeros]

I have an ad-hoc fix here, but it's not perfect: #37995

@aaronfranke: Your ad-hoc fix seems to work indeed(Tested with artifact build).

[Kemeros]

Did more tests.

An empty project doesn't do the problem on version v4.0.dev.custom_build [92a2380]

However. if i load a project, the bug is there.

So i started testing a bit. It's quite easy to reproduce.

Step 1: Make an empty project.
Step 2: Switch to 3D editor.
Step 3: Notice that the bug is NOT present.
Step 4: Add a node. Any base type node will do but i suggest 3D Scene so the editor doesn't switch to 2D.
Step 5: Notice that the bug IS present.
Step 6: Delete the previously added node.
Step 7: The problem stops again.

So adding a node, any node, triggers this issue.

Edit: repro steps triggers the bug because removing all the nodes resizes the viewport. Nodes are not related to the problem.

[Calinou]

So adding a node, any node, triggers this issue.

This may be due to the 3D viewport having a slightly different size due to one of the docks being automatically resized. Try reproducing this after enabling distraction-free mode (Shift + F11 / Ctrl + Shift + F11).

[Kemeros]

This may be due to the 3D viewport having a slightly different size due to one of the docks being automatically resized. Try reproducing this after enabling distraction-free mode (Shift + F11 / Ctrl + Shift + F11).

Tested with both Shift + F11 and Ctrl + Shift + F11:

Same behavior.

Edit:

@Calinou: Now that i think about it. Wouldn't it also affect X and Z if it was the viewport size?

[aaronfranke]

@Kemeros The editor camera doesn't roll, so at the default camera position, the Y axis is always a vertical line on the screen. Then if the screen is a even number of pixels wide, it falls in-between two columns pixels so it disappears. The other axes are rarely perfectly straight and in-between two rows or columns of pixels on the screen, so they don't disappear.

Calinou is correct that whether this bug can be reproduced or not entirely depends on the size of the viewport. Try resizing it, carefully, one pixel at a time.

[Kemeros]

@Kemeros The editor camera doesn't roll, so at the default camera position, the Y axis is always a vertical line on the screen. Then if the screen is a even number of pixels wide, it falls in-between two columns pixels so it disappears. The other axes are rarely perfectly straight and in-between two rows or columns of pixels on the screen, so they don't disappear.

Calinou is correct that whether this bug can be reproduced or not entirely depends on the size of the viewport. Try resizing it, carefully, one pixel at a time.

Ah yes i see. You are both correct. Removing the node actually resize the viewport in a position that the bug doesn't appear. If i play with the viewport, the bug comes back depending on the angle of the camera.

Should the axis lines be a 1 or 2 pixels thicker so it doesn't happen?

[Calinou]

Should the axis lines be a 1 or 2 pixels thicker so it doesn't happen?

We could draw two axis lines close to each other to ensure that at least one of them is always visible. However, I think this will make the origin lines a bit too thick. It's worth trying nonetheless.

[Zylann]

Making lines thicker are just workarounds, they dont seem to adress the root cause. I dont understand how lines are disappearing when lines is a rendering mode where this just can't happen like that Oo
If this is caused by the viewport being stretched such that rendered pixels don't match exactly the area (which can cause aliasing/throttle), then that must be fixed.

[Jasuse]

It seems to be dependent on project config
If renderer/rendering_method="gl_compatibility" (under [rendering]) is present in project,godot, the Y axis just flickers(relatively unnoticable), but if not, it will dissapear at certain angles

[Calinou]

the Y axis just flickers(relatively unnoticable), but if not, it will dissapear at certain angles

This likely means OpenGL and Vulkan have different ways of rounding line widths when drawing lines. OpenGL prefers rounding up (meaning the line goes from 1 to 2 pixels wide), while Vulkan prefers rounding down (meaning the line goes from 1 to 0 pixels wide).

[HeraldOD]

I can reproduce this on a blank project with v4.0.stable.official [92bee43], Windows 10, Nvidia GTX 1650, Forward+ renderer
It seems to only happen around the normal zoom level, it gradually stops flickering when zooming out past ~500u, or in past ~1.8u
My monitor is 1680x1050 if that matters at all

[krummja]

Not sure if this is useful information but I just noticed that the line stops disappearing when the viewport camera's angle is as high or low as it's able to go -- meaning that the Y axis that intersects the XZ plane is no longer visible.

Flickering:

No flickering:

Only difference between the first and second is a minute adjustment in camera angle.

[andersmmg]

This is still an issue, and I've seen it mentioned by people trying out the engine and being confused, notably here. It seems like it would be good to at least work around it soon

[Kemeros]

Still present in 4.1 RC3

[PixelDrennen]

458f17f0fa8bc0a88def6a99227d431f.mp4

Still present in Godot v4.1.1.stable.mono.
I wanted to note something that nobody else has said. The axis only disappears if you're looking at world origin.

Windows 10.0.19045 - Vulkan (Forward+)
dedicated NVIDIA GeForce RTX 2070 SUPER (NVIDIA; 31.0.15.3734)
AMD Ryzen 7 3700X 8-Core Processor (16 Threads)

[aaronfranke]

For those experiencing this issue, please test this PR, which should fix it: #83895

[mahmoudmagdy-7]

I experienced this issue as a new godot user and indeed slightly resizing the left or right panel fixes it

edit: I'm using a nvidia card, as said below that it's related to it

[Calinou]

Do you guys think it could be related to the driver/gpu?

Yes, this issue only occurs on NVIDIA GPUs as described above.

[IGame4FUN]

why not add some red and blue in there and make it subpixel? would solve the issue and make it look better
btw, for me resizing the viewport fixed it as well (nvidia gpu, godot 4.2.1)

[Calinou]

why not add some red and blue in there and make it subpixel? would solve the issue and make it look better btw, for me resizing the viewport fixed it as well (nvidia gpu, godot 4.2.1)

A solution has already been found: #83895