[Libgdx] Flip character without updateWorldTransform() ?

Jamez0r

I have "reflective surfaces" in my game (water / ice), where I draw the Spine character upside-down and with a special shader for texture. Example:

When I render the reflections, I flip it by: skeleton.getRootBone().setScaleY(-skeleton.getRootBone().getScaleY());
After doing that, I have to call: skeleton.updateWorldTransform();

I've been doing some profiling on my game, and updateWorldTransform() is taking a pretty hefty chunk out of my CPU time (I'm guessing partially due to my characters having a decent number of meshes). I have to call updateWorldTransform() at least twice per frame for each character (once for normal rendering, and then once for the reflection).

Is there any way I could eliminate that extra updateWorldTransform() call when I flip the spine character upside down? (Without doing something like rendering the character to an FBO and flipping it, which I believe would be less efficient then the extra updateWorldTransform() call).

Thanks for any suggestions! :clap:

Jamez0r

Nate

Jamez0r wrote
I've been doing some profiling on my game, and updateWorldTransform() is taking a pretty hefty chunk out of my CPU time (I'm guessing partially due to my characters having a decent number of meshes).

Note that updateWorldTransform does calculations only for bones and constraints. Meshes won't affect the CPU time. VertexAttachment computeWorldVertices is where meshes will use CPU, and that happens when the skeleton is rendered.

You can manipulate your Batch matrices to render the skeleton flipped without needing updateWorldTransform, however VertexAttachment computeWorldVertices will still happen for both renders.

You could render to an FBO (see FrameBuffer in libgdx), then render the FBO texture as normal for your character, then again flipped. This is likely most efficient, though has the downsize that you need to size the FBO appropriately. It uses more texture memory, but you likely only need one FBO for your whole app.

Jamez0r

Thanks Nate for the in-depth reply!

Mario

Are you actually having performance issues, or is this a preemptive optimization? It is highly unlikley that calling updateWorldTransform() multiple times per frame will kill your frame rate. An FBO based solution complicates your entire setup, whereas a simple flip and re-render is easy to manage. If you use a profiler, understand that most of the JVM profilers are sampling profilers. Absolute times are not at all accurate, only relative timings should be looked at. And even then, the instrumentation might add overhead, so take profiling results with a grain of salt.