From fc886e3f8d34f7da164cb101588ace34189eaa74 Mon Sep 17 00:00:00 2001
From: Filip Sykala - NTB T15p <Filip.Sykala@prusa3d.cz>
Date: Thu, 24 Nov 2022 11:40:38 +0100
Subject: [PATCH] Fix for adding object with ortho camera

---
 src/slic3r/GUI/CameraUtils.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/slic3r/GUI/CameraUtils.cpp b/src/slic3r/GUI/CameraUtils.cpp
index 7c5616594..c99616b34 100644
--- a/src/slic3r/GUI/CameraUtils.cpp
+++ b/src/slic3r/GUI/CameraUtils.cpp
@@ -104,6 +104,18 @@ Vec2d CameraUtils::get_z0_position(const Camera &camera, const Vec2d & coor)
 {
     Vec3d dir = CameraUtils::create_ray(camera, coor);
     Vec3d p0  = camera.get_position();
+    if (camera.get_type() == Camera::EType::Ortho) { 
+        Matrix4d modelview  = camera.get_view_matrix().matrix();
+        Matrix4d projection = camera.get_projection_matrix().matrix();
+        Vec4i    viewport(camera.get_viewport().data());
+        igl::unproject(Vec3d(coor.x(), viewport[3] - coor.y(), 0.), modelview, projection, viewport, p0);
+    }
+
+    // is approx zero
+    if ((fabs(dir.z()) - 1e-4) < 0)
+        return Vec2d(std::numeric_limits<double>::max(), 
+                     std::numeric_limits<double>::max());
+
     // find position of ray cross plane(z = 0)
     double t  = p0.z() / dir.z();
     Vec3d p = p0 - t * dir;