wip

Author: 375gnu

shaders/star_frag.glsl

@@ -2,10 +2,10 @@ const float degree_per_px = 0.05;
 const float br_limit = 1.0 / (255.0 * 12.92);
 
 varying vec3 v_color;
-varying vec3 v_max_tetha_hk;
+varying vec3 v_tetha_k;
 varying float pointSize;
 
-float psf_square(float theta, float min_theta, float max_theta, float h, float k, float b)
+float psf_square(float theta, float min_theta, float max_theta, float k)
 {
     // Human eye's point source function, optimized to fit a square.
     // Lower limit on brightness and angular size: 1 Vega and 0.05 degrees per pixel.
@@ -16,44 +16,28 @@ float psf_square(float theta, float min_theta, float max_theta, float h, float k
 
     if (theta < max_theta)
     {
-        float brackets = b / (theta - h) - 1.0;
-        return brackets * brackets / k;
+        float brackets = max_theta / theta - 1.0;
+        return k * brackets * brackets;
     }
 
-    return 0.0; // after max_theta function starts to grow again
+    return 0.0;
 }
 
-/*
-float psf_fullscreen(float theta, float min_theta):
-{
-    // Human eye's point source function, optimized to be a full-screen shader.
-    // The price to pay for simplification is a brightness reduction compared to the original PSF.
-
-    if (theta2 < min_theta)
-        return 1; // overexposed
-
-    return 4.43366571e-6 / theta;
-}
-*/
-
 void main(void)
 {
-    float max_theta = v_max_tetha_hk.x;
+    float max_theta = v_tetha_k.x;
     if (max_theta == -1.0)
     {
         gl_FragColor = vec4(v_color, 1.0);
     }
     else
     {
-        float h = v_max_tetha_hk.y;
-        float k = v_max_tetha_hk.z;
-
-        float b = max_theta - h;
-        float min_theta = h + b / (sqrt(k) + 1.0);
-
+        float min_theta = v_tetha_k.y;
+        float k = v_tetha_k.z;
+        // Option 2: glare square render
         vec2 offset = (gl_PointCoord.xy - vec2(0.5)) * pointSize;
-        float theta = length(offset) * degree_per_px;
+        float theta = length(offset) * degree_per_px;    
 
-        gl_FragColor = vec4(v_color * psf_square(theta, min_theta, max_theta, h, k, b), 1.0);
+        gl_FragColor = vec4(v_color * psf_square(theta, min_theta, max_theta, k), 1.0);
     }
 }

shaders/star_vert.glsl

@@ -3,7 +3,7 @@ const float degree_per_px = 0.05;
 const float br_limit = 1.0 / (255.0 * 12.92);
 
 varying vec3 v_color; // 12
-varying vec3 v_max_tetha_hk; // 24
+varying vec3 v_tetha_k; // 24
 varying float pointSize; // 28
 
 uniform vec2 viewportSize;
@@ -23,16 +23,16 @@ void main(void)
     if (check == 0.0)
     {
         pointSize = 1.0;
-        v_max_tetha_hk = vec3(-1.0);
+        v_tetha_k = vec3(-1.0);
     }
     else
     {
-        float max_theta = 0.33435822702992773 * sqrt(max(color0.r, max(color0.g, color0.b))); // glare radius
-        pointSize =  2.0 * ceil(max_theta / degree_per_px);
-
-        float h = 0.0082234880783653 * pow(max_theta, 0.7369983254906639); // h, k, b - common constants, depending originally on star brightness
-        float k = 38581.577272697796 * pow(max_theta, 2.368787717957141);
-        v_max_tetha_hk = vec3(max_theta, h, k);
+        float max_br = sqrt(max(color0.r, max(color0.g, color0.b)));
+        float max_theta = 0.33435822702992773 * sqrt(max_br); // glare radius
+        float k = 3.3e-5 * pow(max_theta, -2.5); // common constant, depending originally on star brightness
+        float min_theta = max_theta / (pow(k, -0.5) + 1.0);
+        pointSize = floor(max_theta / (sqrt(0.5 * br_limit / (k * max_br)) + 1.0) / degree_per_px);
+        v_tetha_k = vec3(max_theta, min_theta, k);
     }
 
     gl_PointSize = pointSize;