Next pass in CanvasItemMaterial seems to do nothing?

[magpie514]

Godot version:
eceba5a

OS/device including version:
OS: Ubuntu Linux 17.10 64b.
OpenGL version string: 4.6.0 NVIDIA 387.34
OpenGL shading language version string: 4.60 NVIDIA
Video device: GeForce GT 630/PCIe/SSE2

Issue description:
I am not entirely sure if this is human error, since the documentation is sparse, but setting a ShaderMaterial as next_step of a CanvasItemMaterial seems to have no effect. I included a little test displaying the shader working when set as material directly, and a "_wrong" version where it's set as the next step.

Steps to reproduce:
Set a shader material as the next_step of a CanvasItemMaterial.

Minimal reproduction project:
b.zip

[eon-s]

When I create a shader and set as canvas_item type, next pass option disappears, I wonder if it works.

[magpie514]

It shows properly for me if setting the material directly. Wanted to have a shader that could be toggled between mix and add blending without having to make another shader file with just that minimal change, as it seems it's not a thing you can change dynamically, but since the whole thing is undocumented I just don't know if I am doing it wrongly, or the feature isn't fully implemented.

[samdze]

Still happens in 3.1 alpha 8dd00ed
The ShaderMaterial in next_pass is ignored.

[kvonspiczak]

version: 3.0.6 stable
windows 10
not entirely sure if my issue is related but i was trying to archieve this effect in my topdown 2d game : https://www.youtube.com/watch?v=_8xqz7LpbTs couldnt get it to work though. i tried adding the SpatialMaterials on the CanvasMaterials of my KinematicBody2D and on a sprite of an object thats rendered in front of my player's kinematicbody. felt like all the settings had no effect at all in my 2d game.

[nobuyukinyuu]

Still happening in 3.1 stable. This is problematic for animated Particle2Ds that used a ShaderMaterial, because CanvasItemMaterial is now required to set animation parameters.

[viktor-ferenczi]

Still happens with Godot 3.1.1. Wanted to pulse the alpha of fireworks particles, but the next_pass shader put into the ParticlesMaterial does nothing.

[LionH]

I confirm. I wanted to stack canvas_item shaders and the next_pass property disappears.

[ghost]

Can confirm! I just started learning shaders and was confused why my shader didn't show up in neither the editor nor the game.

[magpie514]

Seems it's not user error then. Can't wait until it's fixed.

[KoBeWi]

Still valid in 3.2.3

In f733746 both reproduction scenes seem to be broken, so it's impossible to test.