Make sure sorts are deterministic.

3d-viewer/3d_rendering/opengl/render_3d_opengl.cpp

@@ -1137,7 +1137,10 @@ void RENDER_3D_OPENGL::renderTransparentModels( const glm::mat4 &aCameraViewMatr
             [&]( std::pair<const MODELTORENDER *, float>& a,
                  std::pair<const MODELTORENDER *, float>& b )
             {
-                return a.second > b.second;
+                if( a.second != b.second )
+                    return a.second > b.second;
+
+                return a.first > b.first;   // use pointers as a last resort
             } );
 
     // Start rendering calls

3d-viewer/3d_rendering/raytracing/render_3d_raytrace.cpp

@@ -1910,9 +1910,19 @@ void RENDER_3D_RAYTRACE::initializeBlockPositions()
 
     const SFVEC2UI center( m_realBufferSize.x / 2, m_realBufferSize.y / 2 );
     std::sort( m_blockPositions.begin(), m_blockPositions.end(),
-            [&]( const SFVEC2UI& a, const SFVEC2UI& b ) {
+            [&]( const SFVEC2UI& a, const SFVEC2UI& b )
+            {
                 // Sort order: inside out.
-                return distance( a, center ) < distance( b, center );
+                float distanceA = distance( a, center );
+                float distanceB = distance( b, center );
+
+                if( distanceA != distanceB )
+                    return distanceA < distanceB;
+
+                if( a[0] != b[0] )
+                    return a[0] < b[0];
+
+                return a[1] < b[1];
             } );
 
     // Create m_shader buffer