Question about MT light source

[crazy_baboon]

Hi,

I have been learning about MT's lighting system and I struggle to understand what the lighting curve "light_LUT" does. It is defined in https://github.com/minetest/minetest/bl ... /light.cpp. If I compile the code without modification, I get the following:



However, If I zero "light_LUT", i.e. change the "set_light_table" function to:

Code: Select all

void set_light_table(float gamma){
// Lighting curve derivatives
	const float alpha = g_settings->getFloat("lighting_alpha");
	const float beta  = g_settings->getFloat("lighting_beta");
// Lighting curve coefficients
	const float a = alpha + beta - 2.0f;
	const float b = 3.0f - 2.0f * alpha - beta;
	const float c = alpha;
// Mid boost
	const float d = g_settings->getFloat("lighting_boost");
	const float e = g_settings->getFloat("lighting_boost_center");
	const float f = g_settings->getFloat("lighting_boost_spread");
// Gamma correction
	gamma = rangelim(gamma, 0.5f, 3.0f);

	for (size_t i = 0; i < LIGHT_SUN; i++) {
		float x = i;
		x /= LIGHT_SUN;
		float brightness = a * x * x * x + b * x * x + c * x;
		float boost = d * std::exp(-((x - e) * (x - e)) / (2.0f * f * f));
		brightness = powf(brightness + boost, 1.0f / gamma);
		light_LUT[i] = 0;
		if (i > 1 && light_LUT[i] <= light_LUT[i - 1])
			light_LUT[i] = 0; 
	}
	light_LUT[LIGHT_SUN] = 0;
}

I still get some light which appears to be centered on my character and moves with it. I was expecting everything to be dark (notice as well: the axe as gone black):



What is happening here?

Does the lighting curve "light_LUT" only affect sort of ambient light?

What is the light source which appears to be centered on the player?

Thanks

ps:
What does light_LUT stand for?
Wouldn't it be great is instead of having a 20 line copyright header on every single file we had an actually useful description/summary of what that file does? I know copyright notices are important, but they could be moved to the bottom section of every file.

[rubenwardy]

LUT means look up table

The copyright licenses at the top is a legal requirement

[paramat]

There isn't light moving with the player, all you're seeing is fog turning black.
The light curve defines the visual brightness that results from each of the possible node light values 0-15.

[crazy_baboon]

There isn't light moving with the player, all you're seeing is fog turning black.
The light curve defines the visual brightness that results from each of the possible node light values 0-15.

Thanks paramat!

I presume that the light curves only affect the fog.

[paramat]

No the light curve affects the visual brightness of all nodes.
Fog colour is determined by sky or skybox colour so that it always blends into the distance. So i expect you made some kind of mistake.