Camera's matrix exported to alembic has swapped axis #80319

New Issue

Michał Kielak · 2020-09-01T11:29:05+02:00

Michał Kielak commented

2020-09-01 11:29:05 +02:00

System Information
Operating system: Linux-5.4.25-050425-lowlatency-x86_64-with-debian-bullseye-sid 64 Bits
Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 435.21

Blender Version
Broken: version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: 0330d1af29
Worked: (newest version of Blender that worked as expected)

Short description of error
Exported camera which is placed in (0, 0, 0) without any translation, rotation and scale doesn't have diagonal matrix.

Exact steps for others to reproduce the error

Create camera without any translation, rotation, scale
Export with alembic
Read matrix

When I import it in my software and read transformation matrix it looks like this:

0	0	0
0	1	0
-1	0	0
0	0	1

Exported mesh with same transformation has diagonal matrix with 1. As you can see Y and Z are swapped and one column is multiplied by -1. When I import this abc in Maya I can see in properties this swap and multiplication by -1 but it looks like camera is pointing correctly. Blender handles import properly because after importing this abc rotations are correct.

Why does it happen only with camera and not with other objects? Bledner 2.83/2.9 - same effect.

**System Information** Operating system: Linux-5.4.25-050425-lowlatency-x86_64-with-debian-bullseye-sid 64 Bits Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 435.21 **Blender Version** Broken: version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: `0330d1af29` Worked: (newest version of Blender that worked as expected) **Short description of error** Exported camera which is placed in (0, 0, 0) without any translation, rotation and scale doesn't have diagonal matrix. **Exact steps for others to reproduce the error** 1) Create camera without any translation, rotation, scale 2) Export with alembic 3) Read matrix When I import it in my software and read transformation matrix it looks like this: | 1 | 0 | 0 | 0 | | -- | -- | -- | -- | | 0 | 0 | 1 | 0 | | 0 | -1 | 0 | 0 | | 0 | 0 | 0 | 1 | Exported mesh with same transformation has diagonal matrix with 1. As you can see Y and Z are swapped and one column is multiplied by -1. When I import this abc in Maya I can see in properties this swap and multiplication by -1 but it looks like camera is pointing correctly. Blender handles import properly because after importing this abc rotations are correct. Why does it happen only with camera and not with other objects? Bledner 2.83/2.9 - same effect.

Michał Kielak commented

2020-09-01 11:29:05 +02:00

Added subscriber: @michal.kielak

Sybren A. Stüvel commented

2020-09-07 10:56:50 +02:00

Added subscriber: @dr.sybren

Sybren A. Stüvel commented

2020-09-07 10:56:50 +02:00

Changed status from 'Needs Triage' to: 'Archived'

Sybren A. Stüvel closed this issue

2020-09-07 10:56:50 +02:00

Sybren A. Stüvel self-assigned this 2020-09-07 10:56:50 +02:00

Sybren A. Stüvel commented

2020-09-07 10:56:50 +02:00

Maya and Blender have different default camera orientations. See 7c5a44c71f for more details.

Maya and Blender have different default camera orientations. See 7c5a44c71f for more details.

Sybren A. Stüvel commented

2020-09-07 10:59:34 +02:00

To elaborate a bit more: a Blender camera without transformation points straight down. The Alembic file is written in such a way that when Maya (or other software, they seem to expect Maya-orientation too) loads it, it still points straight down.

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Camera's matrix exported to alembic has swapped axis #80319