Understanding Vertex Transforms and Performance
There isn't a specific universal limit for vertex transforms - it depends heavily on your target hardware and frame rate. However, the correlation you're observing between vertex transform count and frame times is expected behavior.
What's Happening
Vertex transforms represent the CPU work needed to calculate each vertex position based on bone influences. With 6,000-9,000 vertex transforms, your CPU is performing thousands of calculations every frame. For a 120 FPS target, you have only 8.3ms per frame total, so 22-28ms processing time would indeed cause significant stuttering.
Optimization Strategies
To reduce vertex transforms, focus on these areas in the Spine Editor:
Use the Prune feature in the Weights view to remove very small bone influences that don't visibly affect the mesh: https://esotericsoftware.com/spine-weights#Prune
Reduce mesh vertex counts - Check if your meshes have more vertices than necessary for the desired visual quality: https://esotericsoftware.com/spine-meshes#Vertex-count
Check the Metrics view in Spine Editor to identify which meshes contribute most to vertex transforms and focus optimization efforts there: https://esotericsoftware.com/spine-metrics
Review bone influences - Meshes influenced by many bones require more calculations per vertex. Reducing the number of bones affecting each vertex helps significantly.
Additional Considerations
- Animation changes shouldn't inherently cause loading delays - the spike you're seeing is likely the CPU work from vertex transforms during complex poses
- Path constraints can also add processing overhead if you're using them
- For 120 FPS targets with complex skeletons, you may need to be quite aggressive with optimization to stay under the frame budget
The performance improvements you've already seen (13k → 6k transforms reducing process time) confirm you're on the right track. Continue optimizing using the tools mentioned above.
