Canvas background in camera environment always drawn on top of 3d geometry

xyz

I'd like to have a shaded color rect as a backdrop for some 3d geometry. According to docs this can be done by setting the background mode of camera's environment to "Canvas" (BG_CANVAS), and adjust Canvas Max Layer property to determine which canvas layers will be drawn in background.

However, when I do that and create a CanvasLayer with a ColorRect child, the rect is always drawn on top of 3d geometry. Curiously, all 3d stuff is drawn as if framebuffer is never cleared inbetween frames.

I tried to play with CanvasLayer's Layer property and Canvas Max Layer property in the environment, as well as moving the CanvasLayer node around in the scene hierarchy, but can't get it to work. It's always drawn over 3d.

cybereality

It doesn't work for me either. Seems broken. You can accomplish the same result using a 2D scene with a 3D viewport, but I'm not sure if that's what you're going for.

xyz

That's unfortunate. Documentation is vague and I couldn't find much on the web. There's something on this very forum from back in 2018 but I'm not quite sure I actually get it.

Anyway, I need full spherical environment for my main scene. Should be a space/starfield type of thing; bunch of stars and maybe some nebulas. Figured to do it procedurally so it's just a shader run on background pixels. I'll probably use a large faraway sprite and let it face the camera... it's somewhat clunky but don't have any better ideas.

Having something like "shader" type of environment background would be nice. A custom procedural could then easily be used instead of default sky.

cybereality

You can do this. Just put a large sphere in the background and do your own shader.

Calinou

Sky shaders will be supported in Godot 4.0, but they can't be backported to Godot 3.x as they rely on new backwards-incompatible rendering features.

xyz

@Calinou So, just to clarify, canvas background is in fact not properly implemented in 3.x, despite the fact that it's listed in docs and appears as an option in the gui?

Calinou

@xyz said: @Calinou So, just to clarify, canvas background is in fact not properly implemented in 3.x, despite the fact that it's listed in docs and appears as an option in the gui?

I think the Canvas background option is really designed for 2D usage first and foremost. For instance, you need to use it to have glow working in a 2D game.

xyz

@cybereality said: You can do this. Just put a large sphere in the background and do your own shader.

Implemented it. Didn't even need a sphere. Simple quad is enough as there are no bitmaps to map. Just 3d noise lookups using pixel world space positions.

It's worth mentioning here that sky background (panorama) lets you equirectangularly map a texture onto an implicit sphere. But texture needs to be enormous in order for stars to look crisp. I instead opted for shader that generates just what is visible in the current frame and projects it onto a backdrop quad parented to camera system.

xyz

@Calinou said:

@xyz said: @Calinou So, just to clarify, canvas background is in fact not properly implemented in 3.x, despite the fact that it's listed in docs and appears as an option in the gui?

I think the Canvas background option is really designed for 2D usage first and foremost. For instance, you need to use it to have glow working in a 2D game.

Right. I guess it'd be in order to add a warning to Environment node reference (under BGMode enum description) saying that BG_CANVAS works only in 2d.

cybereality

Oh yes. Canvas mode does work in 2D, I've tried it for other stuff. I guess 3D is not supported then.

cybereality

@xyz said:

@cybereality said: You can do this. Just put a large sphere in the background and do your own shader.

Implemented it. Didn't even need a sphere. Simple quad is enough as there are no bitmaps to map. Just 3d noise lookups using pixel world space positions.

It's worth mentioning here that sky background (panorama) lets you equirectangularly map a texture onto an implicit sphere. But texture needs to be enormous in order for stars to look crisp. I instead opted for shader that generates just what is visible in the current frame and projects it onto a backdrop quad parented to camera system.

Yes, that is one way. Using a sphere makes it easier if your game has a free camera (like an FPS or flying game). You don't actually need to use the UVs on the sphere, as that would not give you enough resolution. But you can project your own UVs using screen space and map it to any resolution you want. The mesh is just there to provide a continuous backdrop.