1 files changed, 13 insertions, 18 deletions
diff --git a/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl
index 04eb135c90..d1a380bf94 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl
@@ -1,24 +1,24 @@
-/** 
+/**
  * @file class1\deferred\pbrterrainUtilF.glsl
  *
  * $LicenseInfo:firstyear=2023&license=viewerlgpl$
  * Second Life Viewer Source Code
  * Copyright (C) 2023, Linden Research, Inc.
- * 
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation;
  * version 2.1 of the License only.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
- * 
+ *
  * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
  * $/LicenseInfo$
  */
@@ -233,17 +233,12 @@ float terrain_mix(TerrainMix tm, vec4 tms4)
 // Triplanar mapping
 
 // Pre-transformed texture coordinates for each axial uv slice (Packing: xy, yz, (-x)z, unused)
-#define TerrainCoord vec4[2]
+#define TerrainCoord vec4[3]
 
-vec2 _t_uv(vec2 uv_unflipped, float sign_or_zero)
+// If sign_or_zero is positive, use uv_unflippped, otherwise use uv_flipped
+vec2 _t_uv(vec2 uv_unflipped, vec2 uv_flipped, float sign_or_zero)
 {
-    // Handle case where sign is 0
-    float sign = (2.0*sign_or_zero) + 1.0;
-    sign /= abs(sign);
-    // If the vertex normal is negative, flip the texture back
-    // right-side up.
-    vec2 uv = uv_unflipped * vec2(sign, 1);
-    return uv;
+    return mix(uv_flipped, uv_unflipped, max(0.0, sign_or_zero));
 }
 
 vec3 _t_normal_post_1(vec3 vNt0, float sign_or_zero)
@@ -298,9 +293,9 @@ PBRMix terrain_sample_pbr(
 {
     PBRMix mix = init_pbr_mix();
 
-#define get_uv_x() _t_uv(terrain_coord[0].zw, sign(vary_vertex_normal.x))
-#define get_uv_y() _t_uv(terrain_coord[1].xy, sign(vary_vertex_normal.y))
-#define get_uv_z() _t_uv(terrain_coord[0].xy, sign(vary_vertex_normal.z))
+#define get_uv_x() _t_uv(terrain_coord[0].zw, terrain_coord[1].zw, sign(vary_vertex_normal.x))
+#define get_uv_y() _t_uv(terrain_coord[1].xy, terrain_coord[2].xy, sign(vary_vertex_normal.y))
+#define get_uv_z() _t_uv(terrain_coord[0].xy, vec2(0),             sign(vary_vertex_normal.z))
     switch (tw.type & SAMPLE_X)
     {
     case SAMPLE_X:
@@ -379,7 +374,7 @@ PBRMix terrain_sample_pbr(
     default:
         break;
     }
-    
+
     return mix;
 }