X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=lift_gamma_gain_effect.h;h=533a7b2f22aee450c33eef9a41f4a42d657ce7a0;hp=622493491f79c865729542e97dc4eca08efe69a3;hb=0dc1dfe6444a700ebd2c9f006cba000b90c3a7b0;hpb=19a5a44c107dbba0e784ffb7ffcbcd8dd8e91119

diff --git a/lift_gamma_gain_effect.h b/lift_gamma_gain_effect.h
index 6224934..533a7b2 100644
--- a/lift_gamma_gain_effect.h
+++ b/lift_gamma_gain_effect.h
@@ -1,14 +1,30 @@
 #ifndef _LIFT_GAMMA_GAIN_EFFECT_H
 #define _LIFT_GAMMA_GAIN_EFFECT_H 1
 
+// A simple lift/gamma/gain effect, used for color grading.
+//
+// Very roughly speaking, lift=shadows, gamma=midtones and gain=highlights,
+// although all parameters affect the entire curve. Mathematically speaking,
+// it is a bit unusual to look at gamma as a color, but it works pretty well
+// in practice.
+//
+// The classic formula is: output = (gain * (x + lift * (1-x)))^(1/gamma).
+//
+// The lift is actually a case where we actually would _not_ want linear light;
+// since black by definition becomes equal to the lift color, we want lift to
+// be pretty close to black, but in linear light that means lift affects the
+// rest of the curve relatively little. Thus, we actually convert to gamma 2.2
+// before lift, and then back again afterwards. (Gain and gamma are,
+// up to constants, commutative with the de-gamma operation.)
+
 #include "effect.h"
 
 class LiftGammaGainEffect : public Effect {
 public:
 	LiftGammaGainEffect();
-	std::string output_glsl();
+	std::string output_fragment_shader();
 
-	void set_uniforms(GLhandleARB glsl_program_num, const std::string &prefix);
+	void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
 
 private:
 	RGBTriplet lift, gamma, gain;