Transparent Rendering

Dschoonmaker

I have two transparent objects, water and a waterfall. Unfortunately, the waterfall is not visible from underwater and the water is invisible from behind the waterfall. I know this is because I use SCREEN_TEXTURE in the shaders, but is there any way to work around this?

TwistedTwigleg

If you are not already, maybe try using Opaque Pre-pass on one or both of the transparent objects?

In 2D, I know you can use the BackBufferCopy node (documentation) to make a copy of SCREEN_TEXTURE, which you can use to allow both objects to access the SCREEN_TEXTURE, but I'm not sure how you would go about this in 3D.

Dschoonmaker

Opaque pre-pass makes the screen texture black.

TwistedTwigleg

Hmm, so I guess that will not work then.

I have no idea if this would work, or what the performance would look like, but maybe you can pass the Viewport texture to each object, and then use that instead of SCREEN_TEXTURE? One issue I can see with this potential solution is that UI elements would potentially be included, meaning you might need to have a Viewport that is dedicated just to rendering the 3D scene.

I'll keep a look out for better/different solutions.

Dschoonmaker

Yeah, that could work(would probably have some flaws, though).

Dschoonmaker

Is there a way to access the depth texture in the same way?

TwistedTwigleg

@Dschoonmaker said: Is there a way to access the depth texture in the same way?

I do not think so, unfortunately. I think the depth texture can only be accessed once. You could have a separate Viewport that is just used for retrieving the depth texture by having a simple TextureRect node that grabs the depth texture and displays it in the Viewport, allowing it to be used.

That said, there might be a better way. I know in Godot 4.0 there will be more low-level access to the rendering stuff, which probably would make this process easier, but that doesn't help too much with Godot 3. Each Viewport might have its own depth texture separate from the main Viewport's depth texture though.

Dschoonmaker

Oh, yeah that would work. Accessing the depth buffer in 2D would be very useful, e.g. a quad in front of the camera for underwater fog makes the water surface invisible, but that could be worked around with a separate viewport for depth textures.