fixed numerical artifacts in Nil

2019-08-08 00:09:06 +02:00 · 2019-08-08 00:09:06 +02:00 · 5a3a408831
parent 6ab7535088
commit 5a3a408831
1 changed files with 2 additions and 1 deletions
--- a/nonisotropic.cpp
+++ b/nonisotropic.cpp
@ -408,7 +408,8 @@ namespace nilv {

      "for(int it=0; it<50; it++) {"
        "float w = (wmin + wmax) / 2.;"
-        "float z = b * b * (s + (sin(w) - w)/(cos(w) - 1.)) + w;"
+        // the formula after ':' produces visible numerical artifacts for w~0
+        "float z = b * b * (s + (abs(w) < .1 ? w/3. + w*w*w/90. + w*w*w*w*w/2520.: (sin(w) - w)/(cos(w) - 1.))) + w;"
        "if(h[2] > z) wmin = w;"
        "else wmax = w;"
        "}"