Viewport doesn't render at default size [512,512]

[robojeb]

Godot version

4.0-beta1

System information

Windows 10, NVIDIA GeForce RTX 3050 Ti Laptop GPU

Issue description

When creating a SubViewport that renders to a texture if the default viewport size of (512,512) is used the texture renders as all pink, but if the Viewport size is changed (514, 514) it will render properly.

Weirdly, when set to (512,512) it doesn't throw any errors, but when set to another size it throws a bunch of errors:

ERROR: Attempted to use the same texture in framebuffer attachment and a uniform (set: 3, binding: 1), this is not allowed.
   at: (drivers/vulkan/rendering_device_vulkan.cpp:7679)

Steps to reproduce

Create a scene with the following:

• Node3d
  • SubViewport
    • Camera3d
  • MeshInstance [Like a cube, scooch it down the Z axis so the camera(s) can see it]
  • MeshInstance [Plane facing the Z axis and scooted off to the side so it doesn't block the cube]
  • Camera3d [Probably want to scoot it back a bit so you can tell the angle is different from the camera rendering to texture]

Add a script on the root (because of #66247 ) with the following:

extends Node3D

@onready var vp = $SubViewport
@onready var screen = $MeshInstance3d2

# Called when the node enters the scene tree for the first time.
func _ready():
	screen.get_active_material(0).albedo_texture = vp.get_texture()

Minimal reproduction project

OpenTest.zip

[robojeb]

A few updates, on Linux (Manjaro) running Nvidia proprietary drivers for a 1080ti I don't see any size which results in correct rendering.

I also built Godot and ran it under a debugger.
As far as I can tell the Texture is created successfully (rendering_device_vulkan.cpp:1875 returns VK_SUCCESS).
I don't have enough familiarity with the rest of the rendering pipeline to dig further tonight.

[Calinou]

Is the viewport's Update mode set to Always? This is currently required for viewport textures to be generated correctly.

[robojeb]

Setting the value to "Always" makes the texture render in the editor but still shows up as the pink non-Texture when running the scene.
Changing the size does work when running the scene.

Quick Edit: Setting the mode to "Always" also seems to resolve #66247 in the editor (so you get a live texture preview which is nice) but doesn't fix the issue when running the scene.

Second Edit: I re-tested on Linux and now I am also getting the pink texture at the default size, I may have made a mistake in my earlier test.

[robojeb]

I ran Godot built from source in a debugger.

It looks like when the Viewport texture size is default it never goes through texture_create() in the Vulkan renderer.
But when the texture size is non-standard it does hit texture_create().

So the underlying issue may be with how Godot is trying to detect changes in texture size.

[Calinou]

It looks like when the Viewport texture size is default it never goes through texture_create() in the Vulkan renderer.
But when the texture size is non-standard it does hit texture_create().

This sounds similar to what's happening with ReflectionProbes when their extents are set to the default value (which #55178 should incindentally resolve).

[robojeb]

I spent some more time tracing the issue through the debugger.

The issue is that when the RendererViewport is initially created it has a size [0,0].
This means that during creation when executing TextureStorage::_update_render_target() it will early return at rendering_server_default.cpp:2157.

This also happens for the main viewport but as soon as the Window receives a size update it triggers _set_size() on the Viewport which in turn calls TextureStorage::_update_render_target().

Theoretically setting the "Transparent BG" or "MSAA" options to non-defaults should trigger the TextureStorage::_update_render_target() function, but even with one of those settings nothing ever updates the RendererViewport size parameters so it still hits that early return.

This same thing could theoretically happen to the main viewport if it was initialized to a window size [512,512] (and hiDPI is disabled), but in practice it seems like a Window event comes in which has a different p_stretch_transform which is enough to actually cause the size of the main window texture to get set.

The fix probably involves triggering RS::get_singleton()->viewport_set_size(viewport, size.width, size.height) manually as part of a post instantiation step for all Viewport objects, though this is a little wasteful if during scene initialization we end up reducing the size.

[conradax]

The bug is still there in Godot4.0 Beta3.
The SubViewport is always pink with the DEFAULT size of (512,512), But everything works fine after size changed.

Here's my minimal reproduction project: subviewport_bug.zip

If anyone got problem with this bug, Here're some workaround:

• In Editor, set SubViewport Size to anything else then set it back to (512,512)
• In Runtime, add extra line of code like Subviewport.size = Vector2i(512,512)

[alfredbaudisch]

Currently, with Beta3, it seems that no matter the size of the SubViewport, it renders ONLY if it's inside a SubViewportContainer, otherwise it's always pink.

Should this be a new bug report @Calinou?

[Calinou]

Currently, with Beta3, it seems that no matter the size of the SubViewport, it renders ONLY if it's inside a SubViewportContainer, otherwise it's always pink.

Is the viewport's update mode set to Always? See #55471.

[alfredbaudisch]

Currently, with Beta3, it seems that no matter the size of the SubViewport, it renders ONLY if it's inside a SubViewportContainer, otherwise it's always pink.

Is the viewport's update mode set to Always? See #55471.

Only Clear Mode was Always, setting Update Mode to Always made it work again. Thanks.

[marcarneg]

Tried it with Godot 4 beta 17, "Mobile" renderer preset on Win10, dedicated graphics card (not a notebook).
RenderingportBug.zip

Can't get the SubViewPort to work properly. When it works, it doesn't update Material changes, sometimes it just shows a pink texture.

Edit: I just realized, that this ticket was closed already. Sorry!!

[Chevifier]

Tried it with Godot 4 beta 17, "Mobile" renderer preset on Win10, dedicated graphics card (not a notebook). RenderingportBug.zip

Can't get the SubViewPort to work properly. When it works, it doesn't update Material changes, sometimes it just shows a pink texture.

Edit: I just realized, that this ticket was closed already. Sorry!!

Im here trying to use it too. This hasnt been fixed it looks like. Shows up fine in editor but either Pink or Blank at runtime.