I have a very simple scene (one circle) for which I animated the location and size using 4 keyframes (finally it scales down to 0). In blender the animation plays fine, in Krom or the HTML5 nothing is displayed.
Any ideas why this happens (I suppose a bug?).
SimpleAnimationWontPlay.blend (639.5 KB)
Any ideas are very much appreciated
blackno666
Did you use timeline keyframe animation or action (NLE) based animation? Currently my undserstanding is that animation is only supported through actions (armature or spritesheet).
Timeline animation should work. If you want to have control over when to trigger animations you do have to create actions for it, though.
Ah! I thought it didn’t because when I first tried Armory (v 0.5), it certainly didn’t work for me… A quick test with current Git armory shows it working beautifully! 
As to why this particular file isn’t working though, I looked into it and your animation is actually playing. The trouble is that you can’t see it because the only face in your object is an ngon (a face with many sides) and currently there’s a bug in Armory where ngons don’t show because armory works with triangle faces and doesn’t convert ngons into tri’s first.
You can work around this easily, just by applying a triangulate modifier to your object.
Thanks for your help. Converting to tris helps only somewhat: the object now is visible and moves, but in my animation, the object finally scales down to size zero. The complete scaling part of the animation is missing in armory.
Yes, your’re right. In fact, it’s not just the scaling down to zero that’s missing. It seems to not be processing any of the scale keyframes at all. The circle also doesn’t get bigger at the start.
The strange thing is, when I create a test file using locScale keyframes, it works fine, so there’s some weird difference between how you’re doing it and how I am that makes a difference.
I’d file a bug with your file and the versions you’re using of Blender, Armory, your operating system etc.
Note that I used Delta Transforms which you might not have.
Filed a somewhat related bug where even more things are screwed up: Delta Transform animations don't work as expected · Issue #1240 · armory3d/armory · GitHub