From 83c5e81a8b50c29b6b98577791444b2090068d8f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Foucault?= <foucault.clem@gmail.com>
Date: Tue, 5 Aug 2025 11:01:03 +0200
Subject: [PATCH] Fix #143857: View3D smooth interpolation produces invalid
 rv3d.dist values

In the particular case of the report it creates a rv3d with `dist == 0`.

This causes EEVEE to create an invalid projection matrix when
calling `RE_GetWindowMatrixWithOverscan` with a zero `viewplane`.

To avoid this, we check if `rv3d->dist == 0` and don't compute overscan
in this case. This avoid many issues down the line.

Candidate for backporting to 4.5 LTS.

Pull Request: https://projects.blender.org/blender/blender/pulls/143946
---
 .../draw/engines/eevee/eevee_camera.cc        | 24 +++++++++++--------
 .../view3d_navigate_smoothview.cc             |  2 +-
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/source/blender/draw/engines/eevee/eevee_camera.cc b/source/blender/draw/engines/eevee/eevee_camera.cc
index 79833641c24..ddbc4d76db7 100644
--- a/source/blender/draw/engines/eevee/eevee_camera.cc
+++ b/source/blender/draw/engines/eevee/eevee_camera.cc
@@ -145,19 +145,23 @@ void Camera::sync()
       BKE_camera_params_from_view3d(&params, inst_.depsgraph, inst_.v3d, inst_.rv3d);
     }
 
-    BKE_camera_params_compute_viewplane(&params, UNPACK2(display_extent), 1.0f, 1.0f);
+    if (inst_.rv3d->dist > 0.0f && params.lens > 0.0f) {
+      BKE_camera_params_compute_viewplane(&params, UNPACK2(display_extent), 1.0f, 1.0f);
 
-    BKE_camera_params_crop_viewplane(&params.viewplane, UNPACK2(display_extent), &film_rect);
+      BLI_assert(BLI_rctf_size_x(&params.viewplane) > 0.0f);
+      BLI_assert(BLI_rctf_size_y(&params.viewplane) > 0.0f);
 
-    RE_GetWindowMatrixWithOverscan(params.is_ortho,
-                                   params.clip_start,
-                                   params.clip_end,
-                                   params.viewplane,
-                                   overscan_,
-                                   data.winmat.ptr());
+      BKE_camera_params_crop_viewplane(&params.viewplane, UNPACK2(display_extent), &film_rect);
 
-    if (params.lens == 0.0f) {
-      /* Can happen for the case of XR.
+      RE_GetWindowMatrixWithOverscan(params.is_ortho,
+                                     params.clip_start,
+                                     params.clip_end,
+                                     params.viewplane,
+                                     overscan_,
+                                     data.winmat.ptr());
+    }
+    else {
+      /* Can happen for the case of XR or if `rv3d->dist == 0`.
        * In this case the produced winmat is degenerate. So just revert to the input matrix. */
       data.winmat = inst_.drw_view->winmat();
     }
diff --git a/source/blender/editors/space_view3d/view3d_navigate_smoothview.cc b/source/blender/editors/space_view3d/view3d_navigate_smoothview.cc
index 1e7f842c27b..3b20a14324d 100644
--- a/source/blender/editors/space_view3d/view3d_navigate_smoothview.cc
+++ b/source/blender/editors/space_view3d/view3d_navigate_smoothview.cc
@@ -304,7 +304,7 @@ void ED_view3d_smooth_view_ex(
       Object *ob_camera_old_eval = DEG_get_evaluated(depsgraph, sview->camera_old);
       if (sview->ofs != nullptr) {
         sms.src.dist = ED_view3d_offset_distance(
-            ob_camera_old_eval->object_to_world().ptr(), sview->ofs, 0.0f);
+            ob_camera_old_eval->object_to_world().ptr(), sview->ofs, 0);
       }
       ED_view3d_from_object(
           ob_camera_old_eval, sms.src.ofs, sms.src.quat, &sms.src.dist, &sms.src.lens);