Lightning 2D - Change black to white - Godot Community Forums

Lightning 2D - Change black to white

Nano-95

Hi everyone,

I've been messing around with shaders a tiny bit, and decided to make a shader where all of the black pixels in my game turn white, if a boolean is set to true. (I plan on using an animation player to toggle the param between false and true a few times. to give it that lightning feel.)

This is what I got, and actually works nicely!

BUT, it only works for the sprite that I attach this shader script to.

I was hoping to make a screen sized sprite that contains this shader, and everything behind it would react to it.

Here for an example, I added a skull to the sprite texture, and made the rect_size huge, hoping that everything within the rect_size will also react. This sprite contains the script. The boolean is currently false. When i set it to true:

So i was hoping that the things within the rect_size of the sprite would also have the same behavior. Here is what I have.

shader_type canvas_item;

uniform bool lightning = false;

void fragment() {
	vec4 curr_color = texture(TEXTURE,UV); // Get current color of pixel

	if (lightning && curr_color == vec4(0,0,0,1)){
		COLOR = vec4(1, 1, 1, 1);
	}else{
		COLOR = curr_color;
	}
}

I understand that this is happening because of my script, i just dont know how to expand it to things that are underneath the rect_size of the sprite containing the shader.

Any help would be greatly appreciated!

TwistedTwigleg

I'm not sure how performance heavy this would be, but you can use a screen-space shader to handle this. Just make a ColorRect node, set its layout to "full rect", and the try something like the following for the shader:

shader_type canvas_item;
uniform bool lightning = false;
uniform vec4 color_to_replace = vec4(0, 0, 0, 1);
uniform vec4 color_to_use = vec4(1, 1, 1, 1);

void fragment() {
	vec4 curr_color = texture(SCREEN_TEXTURE, SCREEN_UV);
	if (lightning && curr_color == color_to_replace) {
		COLOR = color_to_use;
	} else {
		COLOR = curr_color;
	}
}

On the shader, the only thing I changed was using the screen texture and screen UV coordinates. I also moved the black color to a uniform, so a new vec4 doesn't need to be defined for each fragment call, as it may be a slight optimization, but I'm not sure it was really necessary.

Nano-95

@TwistedTwigleg said: I'm not sure how performance heavy this would be, but you can use a screen-space shader to handle this. Just make a ColorRect node, set its layout to "full rect", and the try something like the following for the shader:
shader_type canvas_item;
uniform bool lightning = false;
uniform vec4 color_to_replace = vec4(0, 0, 0, 1);
uniform vec4 color_to_use = vec4(1, 1, 1, 1);

void fragment() {
	vec4 curr_color = texture(SCREEN_TEXTURE, SCREEN_UV);
	if (lightning && curr_color == color_to_replace) {
		COLOR = color_to_use;
	} else {
		COLOR = curr_color;
	}
}
On the shader, the only thing I changed was using the screen texture and screen UV coordinates. I also moved the black color to a uniform, so a new vec4 doesn't need to be defined for each fragment call, as it may be a slight optimization, but I'm not sure it was really necessary.

Hey thanks so much for the response! I also appreciate your explanation, as it actually helps me understand why you did what you've shown.

So i added your code to a ColorRect and made sure the boolean was true... but it isn't doing anything. I also tried setting the layout to full rect, but no luck :L It seems like it should work from what you explained though...

TwistedTwigleg

Hmm, I probably wrote something wrong. I'll test it and see if I can get it working on a minimal project.

TwistedTwigleg

Okay, I think I found the issue. You don't want to do a direct comparison using == due to floating point precision errors, and instead just want to check if the difference is under a certain amount. After doing this, the shader appears to be working correctly. I attached the project I used :smile:

Nano-95

@TwistedTwigleg said: Okay, I think I found the issue. You don't want to do a direct comparison using == due to floating point precision errors, and instead just want to check if the difference is under a certain amount. After doing this, the shader appears to be working correctly. I attached the project I used :smile:

Aw yes! Thank you!. As a matter of fact, i thought it might be that maybe the == was causing it, so i tried something using <= but after seeing your project, i can see why i was still unable to get it.

Thanks for taking the time to help <3