(This has been composed by ChatGPT.) I am creating a candle flame for a mod in Medieval Engineers: Community Edition, using a CPU particle emitter and a transparent flame material.

The flame looks correct when viewed from approximately one metre away or further. When the camera moves closer than approximately one metre, the flame gradually rotates around its vertical axis as the viewing angle changes. From some viewing directions (i.e.from the front and from the right of the model), it becomes noticeably narrower or nearly edge-on.

The change is smooth rather than a sudden transition. The flame's height remains approximately the same, but its apparent orientation changes. The behaviour is most noticeable from the front and right viewing sectors; from the left or behind, the flame appears correctly oriented.

Tests performed

Disabled the candle's point light: the behaviour remained.

Tested different emitter angle and rotation settings: no improvement.

Tested RotationReference values: alternatives either distorted the flame or made it disappear.

Tested DirToCamera both enabled and disabled: no apparent difference.

Tested several material settings, including NeedSort, AlphaMistingEnable, and IgnoreDepth: no improvement.

Checked the candle model's LOD distances (25 m, 50 m and 125 m), which are much greater than the distance at which the problem occurs.

Corrected the model's flame attachment height separately; this resolved the height issue but did not address the close-range orientation behaviour.

Expected behaviour The flame should maintain a consistent, natural-looking orientation and shape as the camera moves around the candle and approaches it.

Actual behaviour At close range, the flame progressively rotates with the viewing angle and can appear almost edge-on.

Request Could this be investigated as a possible CPU particle billboard orientation or camera-facing behaviour issue?

The effect is being tested in an isolated mod folder, with only the test mod enabled.

I can provide the particle definition, material definition and model for reproduction, and any other information if required.