 #define mediump
 #define highp
 #else
+// Default to high precision variables for the vertex shader.
+// Note that the fragment shader however may default to mediump on mobile for performance,
+// and thus shared uniforms should use a specifier to be consistent in both shaders.
 precision highp float;
 precision highp int;
 #endif

#define mediump
#define highp
#else
#if defined(USE_HIGHP_PRECISION)
precision highp float;
precision highp int;

uniform highp mat4 world_transform;

uniform highp float time;
uniform highp int view_index;

uniform highp vec2 viewport_size;

