Animation Blending

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PlayAnimation demo with animation blending

Animation blending means that the transition between animations is smooth. Without animation blending, the old animation instantly stops and the new animation plays. With animation blending, there is a short time during which the old animation “fades out” (it’s applied with decreasing strength) and the new animation “fades in” (analogously, it’s applied with increasing strength).

The movie below shows this technique in action in new Castle Game Engine. Notice how animation changes are sharp when TransitionDuration is zero, but they are smooth when TransitionDuration is larger. This is especially visible when switching between “Idle” and “Attack” animations on the 3D knight model.

This feature was implemented thanks to Castle Game Engine supporters on Patreon, in particular thanks to Robert Daniel Murphy who wished for it. Thank you! Please support me to see more cool features 🙂

How to use this

Use TCastleSceneCore.PlayAnimation with TPlayAnimationParameters, and set TPlayAnimationParameters.TransitionDuration. TransitionDuration is the time (in seconds) when when previous animation fades-out and new animation fades-in, usually values around 0.1-0.5 make sensible smooth effect. TransitionDuration = 0 (default) means that no animation blending occurs.

We have a new demo examples/play_animation/ to test the PlayAnimation method, including Loop, Forward and TransitionDuration.

Additional cool features of our animation blending

  1. Note that animation blending happens even when you restart the same animation. We show this in the movie by restarting the “Walk” animation — note that “old Walk” blends smoothly into “new, restarted Walk” when Transition is non-zero.
  2. Animation blending works for any field that can be linearly interpolated. So it works for animating translations, rotations, coordinate sets and everything else. It works for mesh deformations, or bone animations produced by Spine. It works for 3D or 2D.

Caveats (aka “things that, sadly, do not work yet”)

  1. For now, the animation blending doesn’t work for animations defined by castle-anim-frames (which you probably use to export animations from Blender). Fixing this requires improving the castle-anim-frames loading a bit.

    Background: Animation blending only works when the same mesh is used by all animation frames, but in case of castle-anim-frames we cheat a little and we have many (precalculated) copies of the mesh. This was supposed to be fixed one day anyway, to decrease memory usage (see the TODO here). It turns out that this fix is also needed to enable animation blending.

  2. For now, there is no way to define TransitionDuration for animations run by our TCreature system (using resource.xml) files. The resources animations (like TCreature) are done a little differently, without directly calling PlayAnimation, and they require a bit different code to make use of animation blending.

Both of these will be fixed one day (AD 1 is a work for ~2 days, AD 2 is a work for ~0.5 day). Let me know if any of this is critical for your project, and I’ll try to make it rather sooner than later! 🙂

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Thoughts about X3D (our scene graph), including PBR (physically-based rendering)

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Castle Game Engine is using X3D as our scene graph. This means that we have a huge number of nodes (like Transform, Shape, IndexedFaceSet) that are nicely documented in the X3D standard. And you use these nodes throughout the engine (by loading files, like X3D files, or constructing the scene using these nodes from Pascal code — see example here or (2D) here).

As our engine grows, and we get more features, I also propose some extensions to X3D, to add more features both to X3D and to Castle Game Engine. I decided to summarize them in the wiki:

Some of these proposals are already implemented in Castle Game Engine (e.g. CommonSurfaceShader, consistent RGB texture treatment, shadows). Some are planned (e.g. PBR, and binary meshes using glTF integration). All the comments are always welcome!

We also talk about these things on x3d-public mailing list, and I encourage everyone to join. If you have an opinion how X3D should look like (in the context of Castle Game Engine usage, or not!), or if you wonder how to do something using X3D — this is the list 🙂

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New server, new fixes and new (small) features

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  1. Our website has moved: It is now on . Our own server (in Los Angeles), our own domain. This makes our website independent from SourceForge. And it opens the door for some cool new features (online 3D models converter, screenshot generator, notifications from WordPress).

    The website on SourceForge continues to work, but it now simply redirects to .

    Our most important downloads (engine, view3dscene) have also moved, to be independent from SourceForge. They are now hosted on GitHub. This makes downloading smoother (no more SourceForge “download redirect” page). BTW, did you know we have a permanent link to the latest CGE download:

  2. Important fixes:

    • Mouse look handling on Windows 10 has been fixed.

    • Fix for Windows Intel GPUs version <= 8: use fixed-function pipeline.

  3. Small new features:

I have some more cool news to share, stay tuned! 🙂

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Mobile View3Dscene Coming Soon

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Let us introduce a new mobile application based fully on Castle Game Engine. It’s a mobile version of our view3Dscene. Basically, it opens scenes in supported 3D formats, and lets user to walk / explore them, navigate through viewpoints and take screenshots. It also includes some demo scenes. As it should be a regular mobile app, not a game, we had to add many new GUI-related features into the engine.

The mobile view3dscene is developed on GitHub by Jan Adamec. We plan to release it soon.

New features available in the engine, added because view3dscene-mobile needed them:

  • Examine camera uses new gesture recognizer to detect pinch-to-zoom and two-finger panning gestures. The panning was possible only with the white round touch control before, so we can get rid of it for Examine camera now.

  • We handle screen DPI setting to scale UI on Android and iOS and present properly sized controls to the user. App works both on tablets and phones in both landscape and portrait modes. The Window.Dpi is now correct on both Android and iOS.

  • New controls: SwitchControl represents variable with on-off state (i.e. a touch-friendly checkbox), and powerful TableView control that has been designed to provide easy way to present dynamic lists with accompanying images or custom controls. It has similar interface as the native iOS UITableView or Android ListView.

  • Option to have the operating system status bar on (with carrier name, clock, battery status). Games usually hide it, which is also the default in our engine, but it may be useful for regular app to leave on. It also applies to the bottom bar with software buttons on Android. To use this in your own applications, set fullscreen_immersive=”false” in CastleEngineManifest.xml and design your UI to leave space at the top following Container.StatusBarHeight.

  • As view3Dscene is an app to view all supported 3D file formats, apps made with Castle Game Engine can now define the file extension associations for Android and iOS in their manifests. See view3dscene-mobile CastleEngineManifest.xml for an example how to define file associations in your own applications.

This post was written mostly by Jan Adamec, who is developing view3dscene-mobile since November 2017. My thousand thanks go to him, both for working on view3dscene-mobile and for implementing many missing necessary features in the engine!

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