I can't get my ship to move over the infinite star shader background?

docwhat

Hello! First time caller. New to Godot.

I have a project at https://github.com/docwhat/screams-into-the-void (the name is just a working title).

I you run it now (at commit bc7d869) and use wasd or the arrow keys, you will get print_rich() output showing the position.

However, the background doesn't move.

Ideally, the ship would remain in the center of the screen while the background moves past. I then plan to add a dynamically added "map" with things like asteroids, etc.

I designed the Shader (stars.gdshader) to cover an infinite plane.

I'm sure I'm just misunderstanding something. But, hey! I learned a bunch about things that didn't help! :smiling

Thanks in advance!

xyz

docwhat What's hash21()?

kuligs2

xyz https://www.shadertoy.com/view/4tXyWN

xyz

kuligs2 The question was meant for the OP to explain in his own words. But now you blew my attempt to determine if the project was vibe-coded 🙂

docwhat

Hah! It was not vibe-coded.

I got the idea from watching The Art of Coding's Starfield tutorial. I changed it so it wouldn't zoom forward but could be used as a parallax far-distant background.

The hash21 function is being used to generate a deterministic random number.

The code is overlabelled and overcommented, so I remember what is going on. It's been a few years since college math. 😁

Note, I do use Copilot to do completion in Neovim. It wasn’t useful at all for gdshader code.

If you look at my other repos, you'll see that I’ve been coding for a bit. 😃

xyz

docwhat Well for the stars to scroll, you need to translate the sampling uv with time.

docwhat

I’m not against having the stars always scrolling down. But then the left/right can’t go off the screen.

I thought there would be an infinite plane with the shader on it. Then the ship could be moved along it.

I thought it might be a UV vs a SCREEN_UV thing. As I understand it:

FRAGCOORD is relative to the visible Node.
SCREEN_UV is relative to the viewport.
I’m unsure about UV, but it seemed wrong.

That’s why I added world_vertex_coords as a render mode.

I’ve noodled around with POV-Ray, 3d Max, and Blender, but I’m not skilled at this.

xyz

docwhat What's an "infinite plane"? Any geometry inside the engine must be finite. If you're sampling some procedural noise, which can be considered almost infinite, just translate the sampling domain.

If you don't fully understand the concept, try it with something simple first. Try to slide some simple procedural strips, or even a seamless bitmap texture.

docwhat

Thanks for all y'all's help!

I went back to the beginning and decided to just have the stars continuously scroll. The point is the player is drifting, so it doesn't matter that they don't control the direction.

You can see my changes here: https://github.com/docwhat/screams-into-the-void/tree/9153219460a57a2d4ff18804f6808f8a3824f32f

I found out my shader had some math bugs, so I went back and re-read the documentation on what FRAGCOORD, UV, etc., actually are, and that helped. I also went back to re-read about OpenGL, since I only attended SIGGRAPH stuff in college.

The real problem, though, was that I had math going out into the weeds, which would eventually cause the shader to stop working.

I kinda wish there was a way to add assertions in the shader during development. I know it would be hard since they all run in parallel and there can be hundreds of millions of them... but still.

Ciao!