4.Animation

4.1. FBX sequence import

When importing animations, I divide them into two forms: alembic and FBX sequences. Among them, character animations are imported in the form of FBX sequences, while fabric simulation and fluid animations are imported through Alembic cache files.

When importing FBX animation sequences, I encountered a technical problem that I had never encountered before. Axial confusion occurred during the import of the animation sequence, and the characters moved along the wrong axis, causing the animation to be completely disordered. After extensive investigation and studying the tutorial, I understood where the problem lies:

Under the Advanced options for importing animations, there is an option called “Use T0 As Ref Pose,” which is not enabled by default. According to relevant tutorials, when exporting animation sequence frames that do not start from frame 0, Unreal Engine (UE) may use an incorrect reference pose. This can result in improper distortion and tearing of the animation. To address this issue, it is necessary to enable this option so that UE uses the first frame of the imported sequence as the model’s reference pose, ensuring the animation is displayed accurately.

4.2. Alembic Animation

For fabric and fluid animations, Alembic cache files must be imported. When synchronizing creature animations with fluid animations, it is crucial to ensure that the scaling ratio and position of both animations are aligned to accurately match the fluid simulation effect. After importing the liquid cache, I encountered challenges in creating the sea surface effect, as the extent of the Alembic cache was insufficient to represent the entire sea surface. Consequently, I utilized the BOSS Ocean plugin to generate an effect resembling an interactive ocean by overlaying fluid patches onto the surface of the Alembic liquid cache file.

Although the final liquid effect is slightly thick and somewhat like “petroleum”, this is also a compromise under the constraints of the production schedule and computer performance. Subsequently, I will continue to conduct research in the workflow of fluid simulation to create better fluid effects.