Fix incorrect crystal geometry

Two triangles in the crystal geometry used for raytracing were
incorrect, leaving two small holes in the crystal. This manifested as
slightly asymmetric brightness distribution of halos with Parry
crystals.

CHANGELOG.md

@@ -20,6 +20,8 @@ and this project adheres to
 - Fixed bug where sky was shown a second time outside field of view with
   equidistant and equal area camera projections
 - Fixed missing prism face distances from save files
+- Fixed bug with slightly incorrect crystal geometry causing uneven brightness
+  distribution with Parry crystal halos
 
 ## 3.2.0 - 2021-03-24
 

src/haloray-core/resources/shaders/raytrace.glsl

@@ -130,11 +130,11 @@ ivec3 triangles[] = ivec3[](
     ivec3(15, 16, 10),
 
     // Face 7 (prism)
-    ivec3(10, 16, 17),
+    ivec3(10, 16, 11),
     ivec3(16, 17, 11),
 
     // Face 8 (prism)
-    ivec3(11, 17, 12),
+    ivec3(11, 17, 6),
     ivec3(17, 12, 6)
 );