Implements #141 normals

Calculate and visualise smoothed normals. The smoothing could be improved to dynamically adjust the smoothing level.

components/renderers/cpp/include/ftl/cuda/normals.hpp

+#ifndef _FTL_CUDA_NORMALS_HPP_
+#define _FTL_CUDA_NORMALS_HPP_
+
+#include <ftl/cuda_common.hpp>
+#include <ftl/rgbd/camera.hpp>
+#include <ftl/cuda_matrix_util.hpp>
+
+namespace ftl {
+namespace cuda {
+
+void normals(ftl::cuda::TextureObject<float4> &output,
+        ftl::cuda::TextureObject<float4> &temp,
+        ftl::cuda::TextureObject<float4> &input, cudaStream_t stream);
+
+void normal_visualise(ftl::cuda::TextureObject<float4> &norm,
+        ftl::cuda::TextureObject<float> &output,
+        const ftl::rgbd::Camera &camera, const float4x4 &pose,
+        cudaStream_t stream);
+
+}
+}
+
+#endif  // _FTL_CUDA_NORMALS_HPP_