Fix the rectilinear camera projection so it doesn't mirror points behind the camera.

This shouldn't be an issue normally as the visual mesh cuts off points that are outside of the camera's view

Author: TrentHouliston

cpp/visualmesh/engine/opencl/kernels/project_rectilinear.cl

@@ -15,6 +15,10 @@
  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#ifndef M_PI_2
+#define M_PI_2 1.57079632679489661923132169163975144
+#endif
+
 /**
  * Projects visual mesh points to a rectilinear camera
  *
@@ -52,7 +56,7 @@ kernel void project_rectilinear(global const Scalar4* points,
     // Calculate some intermediates
     const Scalar theta      = acos(ray.x);
     const Scalar rsin_theta = rsqrt((Scalar)(1.0) - ray.x * ray.x);
-    const Scalar r_u        = f * tan(theta);
+    const Scalar r_u        = f * tan(clamp(theta, 0.0, M_PI_2));
     const Scalar r_d        = r_u
                        * (1.0                                                                  //
                           + k.x * (r_u * r_u)                                                  //

cpp/visualmesh/utility/projection.hpp

@@ -50,7 +50,7 @@ namespace equisolid {
 namespace rectilinear {
     template <typename Scalar>
     inline Scalar r(const Scalar& theta, const Scalar& f) {
-        return f * std::tan(theta);
+        return f * std::tan(std::min(std::max(theta, Scalar(0.0)), Scalar(M_PI_2)));
     }
 
     template <typename Scalar>

training/projection/__init__.py

@@ -1,3 +1,5 @@
+import math
+
 import tensorflow as tf
 
 
@@ -26,7 +28,7 @@ def _equidistant_r(theta, f):
 
 
 def _rectilinear_r(theta, f):
-    return f * tf.math.tan(theta)
+    return f * tf.math.tan(tf.clip_by_value(theta, 0.0, math.pi * 0.5))
 
 
 def _equisolid_r(theta, f):