The issue of visible gaps or lines at character joints in Spine animations when using the Swift runtime could be related to how the attachments are rendered or how the meshes are set up. This problem might be due to "z-fighting" or incorrect attachment setup, which can cause rendering artifacts. To address this, you can try adjusting the rendering order or slightly offsetting the attachments on the z-axis to prevent z-fighting. Additionally, ensure that the meshes and attachments are correctly set up in the Spine editor, and check for any warnings or errors that might indicate issues with the mesh or bone setup.

A screenshot would help, but it's most likely a problem with premultiplied alpha. Eg, not using PMA, using PMA but not rendering with PMA enabled, applying PMA twice, etc. Xcode is notorious for applying PMA, you likely need to disable that.

Maybe you could use non-PMA images and let Xcode apply PMA, instead of using the Spine texture packer to apply PMA.

hechang Is there a process in the loading process that modifies the image files, such as making them lighter? If there is a process that resaves the texture atlas page after it has been exported from Spine, the color information of the translucent pixels may be lost, and it may cause artifacts in areas where translucent pixels are mixed, such as image borders.