ref: f476e77f1216de039a19dc1849ddda3971332c34
parent: d9d02c1e3bfea2805a241fec8f6036389da47fb1
author: qwx <qwx@sciops.net>
date: Wed Oct 7 08:03:04 EDT 2020
grp: adjust alpha curve for better sprite rendition scv engine glow looks slightly better this way
--- a/utils/grp.c
+++ b/utils/grp.c
@@ -106,9 +106,13 @@
switch(npal){case 63:
if(i > 47)
- a = (0xff + 1) / (1 + exp(-i + 48 - 3.4) / 0.75);
+ a = 0xff / (1 + exp(-i + 48 - 3.4) / 0.75);
+ /* logistic growth function
+ * max / (1 + exp(-x + xofs) / slope) + yofs
+ * fplot -r '0:47 0:255' '255 / (1 + exp((20 - x) / 4)) + 0'
+ */
else
- a = (0xff + 1) / (1 + exp(-i + 10.0) / 2.2);
+ a = (0xff + 1) / (1 + exp((16 - i) / 3.5)) + 0;
break;
/* FIXME */
case 40: a = i < 33 ? 0xff * i / 32 : 0xff * (6 - (i - 33)) / 6; break;