LibGDX, Box2D Lighting. Turning off Box2DLights for certain sprites, not bodies

Newbie & Debugging Questions
#1

Hi, I’ve been trying to find a way to disable Box2DLights for certain sprites, while still using Box2DLights for other bodies and sprites.

I have a starry background and a ship. It is a top down kinda game. The problem is where the lighting casts shadows over the background stars.
I can’t exactly set ambient lighting as I need the pitch black areas. I’ve looked around and bumped into a few things. Blending, filtering and shaders.
I have no idea how shaders/GLSL work but it seems to be what I should look more into :confused:
I’m actually already using filtering for certain bodies, the floor fixture for example.
Of course I don’t know what’s going on in the background, but to turn off Box2DLights for a texture seems like it would be a simple task ::slight_smile:

I think blending is a good option also. My guess, from what I’ve discovered is there might be a way to render the lighting to a buffer or something
and then use blending to hide lights and shadows on certain sprite textures.

Otherwise I might have missed something I dunno.

My render loop goes like this



	public void render(float delta){
		Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
		
		cam2D.update();
		camBG.update();
		
		batchBG.setProjectionMatrix(camBG.combined);
		batch2D.setProjectionMatrix(cam2D.combined);
		ship1.update(Main.cameraZoom);
		background.update();
		character.update(cam2D.position.x, cam2D.position.y);

		if(GameInputs.keyPressed(Keys.ESCAPE))
			main.setScreen(new LaunchScene(main));

		world.step(12, 80, 80);
		
		shipLight.setPosition(ship1.body.getWorldCenter().x, ship1.body.getWorldCenter().y);
		playerLight.setPosition(character.body.getWorldCenter().x+character.force.x*99999, character.body.getWorldCenter().y+character.force.y*99999);
		
		batchBG.begin();
		background.render(batchBG);
		batchBG.end();

		batch2D.begin();
		ship1.render(batch2D);
		character.render(batch2D);
		batch2D.end();
		
		rayHandler.updateAndRender();
		rayHandler.setCombinedMatrix(cam2D);
	}
#2

Yes you can, just set the RGB values to 0.0. It’ll be pitch black.

#3

Sorry, I meant I can’t have ambient lighting above 0. My question is how to turn off Box2DLights for certain textures. Right now it looks like this.

1268×763 71.2 KB

It is supposed to look more like this but not with the stars over the ship textures.

1268×761 76.5 KB

#4

Draw the stars after the rayHandler has been drawn? I don’t believe there is a way to select some “textures” to not be affected by the light.

#5

That is how I made the second image in my last response. There is a hacky way, like not drawing a star if over a ship texture. But there will be bigger sprites than stars in space eventually. I think I really have to learn some kind of blending or shader programming for proper results. I shall do more digging. Thanks for the replies btw!

#6

woa, is it just me or is there some kind of optical illusion in your first image? :slight_smile:

For your question: Maybe a stencil buffer will help you? You could draw the sprites you want light for in the stencil buffer and then you can draw the stars on top of that to everywhere where you didn’t draw the stencil.

Can’t articulate myself better right now - it’s late, I need to go to bed :wink: