Viewport data not being sent to shader parameter in runtime

[AssjackGames]

Godot version:

3.0 RC2

OS/device including version:

Windows 10
AMD Radeon HD 7700 Series
Driver version: Adrenalin (17.12.1)

Issue description:

Viewports aren't properly sending their output to shaders (at least in 2D, haven't tested for 3D). While it appears to work fine in-editor, when the scene is ran the output is all black.

Steps to reproduce:

First I created an empty scene, root type node2D. I made a viewport, set it up, and added an image under it, setting the texture to a png. I then made a new sprite outside that viewport and set the texture to the viewport output to test if it was outputting fine. I ran the scene and all seemed to work, I saw the circle image.

I then replaced the texture of the output image with a blank png (Color(1, 1 ,1 ,1)) the size of the screen, and created a new shader, using this code:

shader_type canvas_item;

uniform sampler2D mask;

void fragment(){
	COLOR = texture(mask, UV);
}

Then I set the parameter mask to the viewport output, and I saw the results immediately in the editor, however when I run the scene the output is all black. I also tried sending the viewport data through gdScript using get_texture, and it too led to the black screen output.

Minimal reproduction project:

Test project attached. I created two output sprites for it, one direct from the viewport, one with the shader. With this bug any shader needing more than a single viewport won't work.

Viewport Bug.zip

[DoctorAlpaca]

Of note, when also using the same texture to a sprite the correct texture gets send to the shader. I'm guessing the shader handling code doesn't correctly tell the texture to update itself.

[AssjackGames]

Not that it was on the agenda, just thought I'd mention that the bug exists in 3.0 stable too.

[AssjackGames]

Not sure if this is related, but when I try to set an image texture to a new ViewportTexture via gdScript (changing the viewport_texture property too of course) it shows nothing when I run it. I know the viewport works fine, and oddly enough when I make the sprite through the editor, set it to the viewport, clear the path and set the path through gdScript it shows fine too. Problem seems to be initiating a new ViewportTexture through code. Should this be a new ticket?

[AssjackGames]

My tests have been completely in 2D, should that make any difference in diagnosis

[akien-mga]

Related to #7998.

[kubecz3k]

Related to #17651

[kiiada]

Confirming this issue exists in 3D as well.

My scene structure is:

-PlaneMesh (material settings: albedo viewport texture, transparent flag checked, billboard)
   '- Viewport (set to transparent bg, update mode to always)
       '- Control
           '-Label

As described, the label node text appears on the texture in the editor, but when a scene containing the node is run the texture is black without the label text

[reduz]

This is not a bug (Material was not set as local to scene), but usability was pretty bad to let you know what was going on.
Added warnings to avoid you when creating a ViewporTextures if most common conditions are not met instead.