From 6c40adcc360b4971a031e52f0260ecc768ff110a Mon Sep 17 00:00:00 2001
From: Miguel Pozo <pragma37@gmail.com>
Date: Wed, 13 Dec 2023 17:46:55 +0100
Subject: [PATCH] Fix: GPU: from_up_axis

glsl sign can return 0.
Fixes surfels display when normal.z == 0.
---
 .../blender/gpu/shaders/common/gpu_shader_math_matrix_lib.glsl  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/blender/gpu/shaders/common/gpu_shader_math_matrix_lib.glsl b/source/blender/gpu/shaders/common/gpu_shader_math_matrix_lib.glsl
index adb600cb665..f521ef71605 100644
--- a/source/blender/gpu/shaders/common/gpu_shader_math_matrix_lib.glsl
+++ b/source/blender/gpu/shaders/common/gpu_shader_math_matrix_lib.glsl
@@ -1029,7 +1029,7 @@ mat4x4 from_loc_rot_scale(vec3 location, AxisAngle rotation, vec3 scale)
 mat3x3 from_up_axis(vec3 up)
 {
   /* Duff, Tom, et al. "Building an orthonormal basis, revisited." JCGT 6.1 (2017). */
-  float z_sign = sign(up.z);
+  float z_sign = up.z >= 0.0 ? 1.0 : -1.0;
   float a = -1.0 / (z_sign + up.z);
   float b = up.x * up.y * a;