fx: move tonemap shaders to engine art dir

demos/06-material.c

@@ -28,7 +28,7 @@ int main() {
 
     // fx: load all post fx files in all subdirs.
     fx_load("fx**.fs");
-    fx_enable(fx_find("fxAces.fs"), 1);
+    fx_enable(fx_find("fxTonemapACES.fs"), 1);
 
     // load video, RGB texture, no audio
     video_t *v = video( "pexels-pachon-in-motion-17486489.mp4", VIDEO_RGB | VIDEO_NO_AUDIO | VIDEO_LOOP ); video_seek(v, 30);

demos/art/fx/fxAces.fs

@@ -1,16 +0,0 @@
-out vec4 color;
-
-void main(void) {
-    vec2 uv = TEXCOORD.st;
-    vec3 src = texture2D(iChannel0, uv).rgb;
-    vec3 x = src;
-
-    // aces film (CC0, src: https://knarkowicz.wordpress.com/2016/01/06/aces-filmic-tone-mapping-curve/)
-    float a = 2.51f;
-    float b = 0.03f;
-    float c = 2.43f;
-    float d = 0.59f;
-    float e = 0.14f;
-    src = clamp((x*(a*x+b))/(x*(c*x+d)+e), 0.0, 1.0);
-    color = vec4(src, 1.0);
-}

engine/art/fx/fxTonemapUchimura.fs

@@ -0,0 +1,41 @@
+// Uchimura 2017, "HDR theory and practice"
+// Math: https://www.desmos.com/calculator/gslcdxvipg
+// Source: https://www.slideshare.net/nikuque/hdr-theory-and-practicce-jp
+vec3 uchimura(vec3 x, float P, float a, float m, float l, float c, float b) {
+  float l0 = ((P - m) * l) / a;
+  float L0 = m - m / a;
+  float L1 = m + (1.0 - m) / a;
+  float S0 = m + l0;
+  float S1 = m + a * l0;
+  float C2 = (a * P) / (P - S1);
+  float CP = -C2 / P;
+
+  vec3 w0 = vec3(1.0 - smoothstep(0.0, m, x));
+  vec3 w2 = vec3(step(m + l0, x));
+  vec3 w1 = vec3(1.0 - w0 - w2);
+
+  vec3 T = vec3(m * pow(x / m, vec3(c)) + b);
+  vec3 S = vec3(P - (P - S1) * exp(CP * (x - S0)));
+  vec3 L = vec3(m + a * (x - m));
+
+  return T * w0 + L * w1 + S * w2;
+}
+
+vec3 uchimura(vec3 x) {
+  const float P = 1.0;  // max display brightness
+  const float a = 1.0;  // contrast
+  const float m = 0.22; // linear section start
+  const float l = 0.4;  // linear section length
+  const float c = 1.33; // black
+  const float b = 0.0;  // pedestal
+
+  return uchimura(x, P, a, m, l, c, b);
+}
+
+out vec4 color;
+
+void main(void) {
+    vec2 uv = TEXCOORD.st;
+    vec4 src = texture2D(iChannel0, uv);
+    color = vec4( uchimura(src.xyz), src.a);
+}