From a92f2d1f9fdf04f64790390ae18050b9b80dd453 Mon Sep 17 00:00:00 2001
From: Gavin Ridley <gavin.keith.ridley@gmail.com>
Date: Wed, 5 Apr 2023 11:50:45 -0400
Subject: [PATCH] avoid segfault with idiomatic thresholding, rays through
 pixel centers

---
 src/plot.cpp                                         | 12 +++++++-----
 .../plot_projections/results_true.dat                |  2 +-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/plot.cpp b/src/plot.cpp
index 8912bb9b0..1f629e901 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -1273,8 +1273,10 @@ void ProjectionPlot::create_output() const
 
           // Generate the starting position/direction of the ray
           if (orthographic_width_ == 0.0) { // perspective projection
-            double this_phi = -horiz_fov_radians / 2.0 + dphi * horiz;
-            double this_mu = -vert_fov_radians / 2.0 + dmu * vert + M_PI / 2.0;
+            double this_phi =
+              -horiz_fov_radians / 2.0 + dphi * horiz + 0.5 * dphi;
+            double this_mu =
+              -vert_fov_radians / 2.0 + dmu * vert + M_PI / 2.0 + 0.5 * dmu;
             Direction camera_local_vec;
             camera_local_vec.x = std::cos(this_phi) * std::sin(this_mu);
             camera_local_vec.y = std::sin(this_phi) * std::sin(this_mu);
@@ -1436,9 +1438,9 @@ void ProjectionPlot::create_output() const
             if (i * i + j * j < wireframe_thickness_ * wireframe_thickness_) {
 
               // Check if wireframe pixel is out of bounds
-              int w_i = std::max(std::min(horiz + i, pixels_[0]), 0);
-              int w_j = std::max(std::min(vert + j, pixels_[1]), 0);
-              data(i, j) = wireframe_color_;
+              int w_i = std::max(std::min(horiz + i, pixels_[0] - 1), 0);
+              int w_j = std::max(std::min(vert + j, pixels_[1] - 1), 0);
+              data(w_i, w_j) = wireframe_color_;
             }
       }
     }
diff --git a/tests/regression_tests/plot_projections/results_true.dat b/tests/regression_tests/plot_projections/results_true.dat
index 64410ac93..a2cb57b1e 100644
--- a/tests/regression_tests/plot_projections/results_true.dat
+++ b/tests/regression_tests/plot_projections/results_true.dat
@@ -1 +1 @@
-a8c00451d0766c73a1c03769a12524fa4e08246e253fedd9f75c1b81889d3a71ff7782197090ca3aff4f58d8c863203028347338b3a1e3d78af14e3716482b96
\ No newline at end of file
+6448093f8acaa2af02452ec1b29461ffaf89628bb002cc8873a3a6831fe5d613645a197033597e5a064896388f19d0782f05e78ce474354ae2a76c35ff4551d7
\ No newline at end of file