Change Details

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71 **Blender Version** Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: `rB3e85bb34d0d7` Worked: (newest version of Blender that worked as expected) **Short description of error** The twist of a mesh deformed with the Particle Instance Modifier with the Along Path option seems broken, more noticeable with steep curvature in hairs. I compare it to the Curve Deform modifier as an example of proper deformation. Now, you may say it's an unfair comparison given that curves have an explicit twist that you can modify, unlike hairs. But even without controlling the initial twist of the hair, it's broken in a couple of ways. First, it deforms the mesh unevenly, with some vertices twisting more than others, even in a case where vertices are completely equidistant around the origin and both origins are aligned, like the cube in this image. The selected face and the edgeloop here should be squares but aren't, unlike in the curve deform modifier {F9487914} Second, when changing the length with the Position Slider, the whole thing seems to change twist at once. Instead of having a consistent twist on each point of the path {F9487901} As a side note, when using Along Path, finding how to orient your mesh to the hair is unintuitive, always using the global Y axis as the length axis in which I added subdivisions but then twisting weirdly when changing the Axis option in the modifier, I settled for Z in this example. **Exact steps for others to reproduce the error** Attached is the same file used in the video, you can open it and move the Position slider in the Particle Instance Modifier, the scale of the Curve Deform modifier example is driven by it so you can see both changing in real time. {F9487921} Why do I think this is happening? Well, if you select the object with the particle system, go to the particle properties, and change the length of the hair under the Render>Timing>End subpanel, you can see the problem is the same, basically the twist changes with length. Maybe the modifier should do something different and get the twist from the whole length particle and then scale the mesh before deforming or something like that, idk

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71 **Blender Version** Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: `rB3e85bb34d0d7` Worked: (newest version of Blender that worked as expected) **Short description of error** The twist of a mesh deformed with the Particle Instance Modifier with the Along Path option seems broken, more noticeable with steep curvature in hairs. I compare it to the Curve Deform modifier as an example of proper deformation. Now, you may say it's an unfair comparison given that curves have an explicit twist that you can modify, unlike hairs. But even without controlling the initial twist of the hair, it's broken in a couple of ways. First, it deforms the mesh unevenly, with some vertices twisting more than others, even in a case where vertices are completely equidistant around the origin and both origins are aligned, like the cube in this image. The selected face and the edgeloop here should be squares but aren't, unlike in the curve deform modifier {F9487914} Second, when changing the length with the Position Slider, the whole thing seems to change twist at once. Instead of having a consistent twist on each point of the path {F9487901} As a side note, when using Along Path, finding how to orient your mesh to the hair is unintuitive, always using the global Y axis as the length axis in which I added subdivisions but then twisting weirdly when changing the Axis option in the modifier, I settled for Z in this example. **Exact steps for others to reproduce the error** Attached is the same file used in the video, you can open it and move the Position slider in the Particle Instance Modifier, the scale of the Curve Deform modifier example is driven by it so you can see both changing in real time. {F9487921} Why do I think this is happening? Well, if you select the object with the particle system, go to the particle properties, and change the length of the hair under the Render>Timing>End subpanel, you can see the problem is the same, basically the twist changes with length. Maybe the modifier should do something different and get the twist from the whole length particle and then scale the mesh instance before deforming or something like that, idk

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71 **Blender Version** Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: `rB3e85bb34d0d7` Worked: (newest version of Blender that worked as expected) **Short description of error** The twist of a mesh deformed with the Particle Instance Modifier with the Along Path option seems broken, more noticeable with steep curvature in hairs. I compare it to the Curve Deform modifier as an example of proper deformation. Now, you may say it's an unfair comparison given that curves have an explicit twist that you can modify, unlike hairs. But even without controlling the initial twist of the hair, it's broken in a couple of ways. First, it deforms the mesh unevenly, with some vertices twisting more than others, even in a case where vertices are completely equidistant around the origin and both origins are aligned, like the cube in this image. The selected face and the edgeloop here should be squares but aren't, unlike in the curve deform modifier {F9487914} Second, when changing the length with the Position Slider, the whole thing seems to change twist at once. Instead of having a consistent twist on each point of the path {F9487901} As a side note, when using Along Path, finding how to orient your mesh to the hair is unintuitive, always using the global Y axis as the length axis in which I added subdivisions but then twisting weirdly when changing the Axis option in the modifier, I settled for Z in this example. **Exact steps for others to reproduce the error** Attached is the same file used in the video, you can open it and move the Position slider in the Particle Instance Modifier, the scale of the Curve Deform modifier example is driven by it so you can see both changing in real time. {F9487921} Why do I think this is happening? Well, if you select the object with the particle system, go to the particle properties, and change the length of the hair under the Render>Timing>End subpanel, you can see the problem is the same, basically the twist changes with length. Maybe the modifier should do something different and get the twist from the whole length particle and then scale the mesh instance before deforming or something like that, idk