message: 32-bit suffices
diff: #ifndef VSNRAY_DETAIL_WHITTED_INL
  #define VSNRAY_DETAIL_WHITTED_INL 1
  -#include <cstddef>
  #include <type_traits>
  #include <visionaray/array.h>
  @@ -172,7 +171,7 @@ inline auto specular_bounce(
  }
  template <
  - size_t N,
  + unsigned N,
  typename ...Ts,
  typename T,
  typename = typename std::enable_if<simd::is_simd_vector<T>::value>::type
  @@ -195,7 +194,7 @@ inline auto specular_bounce(
  float_array kr;
  float_array kt;
  - for (size_t i = 0; i < N; ++i)
  + for (unsigned i = 0; i < N; ++i)
  {
  auto res = specular_bounce(ms[i], vds[i], ns[i]);
  refl_dir[i] = res.reflected_dir;
  