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[Gerrard]

Hello !
I'm new here and I speak french usually, so I hope my post will be fine

I'm working on a game called Pankapu, a 2D platformer. Maybe you already heard about it.
In the game, we have a level in the darkness, and there is a light that follows the character in order to see something.

My shader is simple, it renders all dark except where I put these lights. I use the alpha channel to know how dark it must be (1 => no darkess, 0 => full darkness). It works fine but I have a little problem : when two lights overlap themselves, I take the highest value (seems logical) but as you can see in the screenshot, it looks a little bit weird.

How do you think I can improve that ?
By taking the average around the pixel rendered ?
Or maybe I need to use another alpha blending method than taking the max value ?

Thanks !

[zilluss]

Add the values of the light so two lights will merge into a brighter one.

[Gerrard]

Thanks, but I already tried that (i forgot to mention it) and it's really not the kind of rendering I want... It doesn't seem natural at all if I add the two lights.

[zilluss]

How do you render the lights? Do you pass them as attributes/uniforms to your shader? Then you know for each pixel how near the closest light is. If there are multiple lights nearby increase the light value of the pixel a little bit, to simulate overlapping lights without the hard look of additive blending.

[Gerrard]

For now, I render all the lights in a RenderTexture, and after that I use that texture to darken or not the scene.
Your approach seems great, I'll see if I can do something like that ! Thanks.

[epcc]

Additive blending is correct. If it looks weird, it's probably because your light texture is linear instead of quadratic.
It's hard to explain, so see the example textures instead.
Linear:


Quadratic:


Here's the code I generated these images with:
https://gist.github.com/johann2/5ff1546548cc7b2d3144#file-light-py

[Trent]

Quadratic:

Think you can generate a large version of this? I don't feel like learning the python setup. 

[Polly]

Think you can generate a large version of this? I don't feel like learning the python setup.

You might want to generate the texture in your engine rather than importing a bitmap ( and use dithering ). Regardless .. here you go.

[Trent]

Thanks man.