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@@ -29,6 +29,28 @@ static u8 light_LUT[LIGHT_SUN + 1];
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// The const ref to light_LUT is what is actually used in the code
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const u8 *light_decode_table = light_LUT;
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+struct LightingParams {
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+ float a, b, c; // polynomial coefficients
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+ float boost, center, sigma; // normal boost parameters
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+ float gamma;
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+};
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+
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+static LightingParams params;
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+
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+float decode_light_f(float x)
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+{
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+ if (x >= 1.0f) // x is equal to 1.0f half the time
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+ return 1.0f;
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+ x = std::fmax(x, 0.0f);
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+ float brightness = ((params.a * x + params.b) * x + params.c) * x;
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+ brightness += params.boost * std::exp(-0.5f * sqr((x - params.center) / params.sigma));
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+ if (brightness <= 0.0f) // may happen if parameters are insane
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+ return 0.0f;
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+ if (brightness >= 1.0f)
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+ return 1.0f;
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+ return powf(brightness, 1.0f / params.gamma);
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+}
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+
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// Initialize or update the light value tables using the specified gamma
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void set_light_table(float gamma)
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{
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@@ -36,26 +58,29 @@ void set_light_table(float gamma)
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const float alpha = g_settings->getFloat("lighting_alpha");
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const float beta = g_settings->getFloat("lighting_beta");
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// Lighting curve coefficients
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- const float a = alpha + beta - 2.0f;
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- const float b = 3.0f - 2.0f * alpha - beta;
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- const float c = alpha;
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+ params.a = alpha + beta - 2.0f;
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+ params.b = 3.0f - 2.0f * alpha - beta;
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+ params.c = alpha;
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// Mid boost
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- const float d = g_settings->getFloat("lighting_boost");
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- const float e = g_settings->getFloat("lighting_boost_center");
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- const float f = g_settings->getFloat("lighting_boost_spread");
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+ params.boost = g_settings->getFloat("lighting_boost");
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+ params.center = g_settings->getFloat("lighting_boost_center");
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+ params.sigma = g_settings->getFloat("lighting_boost_spread");
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// Gamma correction
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- gamma = rangelim(gamma, 0.5f, 3.0f);
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-
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- for (size_t i = 0; i < LIGHT_SUN; i++) {
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- float x = i;
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- x /= LIGHT_SUN;
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- float brightness = a * x * x * x + b * x * x + c * x;
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- float boost = d * std::exp(-((x - e) * (x - e)) / (2.0f * f * f));
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- brightness = powf(brightness + boost, 1.0f / gamma);
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- light_LUT[i] = rangelim((u32)(255.0f * brightness), 0, 255);
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+ params.gamma = rangelim(gamma, 0.5f, 3.0f);
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+
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+// Boundary values should be fixed
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+ light_LUT[0] = 0;
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+ light_LUT[LIGHT_SUN] = 255;
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+
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+ for (size_t i = 1; i < LIGHT_SUN; i++) {
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+ float brightness = decode_light_f((float)i / LIGHT_SUN);
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+ // Strictly speaking, rangelim is not necessary here—if the implementation
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+ // is conforming. But we don’t want problems in any case.
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+ light_LUT[i] = rangelim((s32)(255.0f * brightness), 0, 255);
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+ // Ensure light brightens with each level
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if (i > 1 && light_LUT[i] <= light_LUT[i - 1])
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light_LUT[i] = light_LUT[i - 1] + 1;
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}
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- light_LUT[LIGHT_SUN] = 255;
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}
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+
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#endif
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