Hoe can Gamemaker do all that without stuttering?
Big backgrounds and sprite, plus double drawing.
I think you're underestimating GameMaker. I have dozens of huge sprites and thousands of smaller ones drawing all the time, all at a silky smooth 1080p60.
Can anyone with some Spine 2d experience (this might include you two at team Nethermind) explain to me the features list here, or at least, what are the most important features you're looking at?
https://esotericsoftware.com/spine-purchase
I think free form deformation is an important one, but I'm trying to internalize what some of these others are. The Stencyl guy asked me what would be most important to try and bring in support for since we're discussing Spine integration, and I have no practical experience with the program yet.
http://esotericsoftware.com/spine-in-depth
Ghosting is something I don't use. It's a previz of the next and/or previous frame in the animator, not part of in-game rendering. Instead, I just toggle between adjacent frames with hotkeys (WASD is used to control next/prev keyframe and playback, which is super comfortable).
Meshes in this context reduce overdraw by making a simple poly mesh over the shape of your sprite rather than using the whole rectangle.
I design most models to not need free form deformation, but it's handy for things that need to stretch and bend in a non-uniform way.
Inverse Kinematics isn't supported in GameMaker, which sucks to be frank, but the idea there is aiming a pair of connected bones at another point and letting the computer figure out what the proper angles should be. This is usually used to make feet locked to the terrain and have head/eye-tracking work, but it can be used in animation based contexts as well.
Take this unicycle mime that I have. Ideally, the legs should be locked to the feet, which are locked to the pedals, which is locked to the shaft, which is locked to the seat, which is locked to the legs. It's a loop, which the computer wouldn't be able to work out, so I have to split it up some how. With IK, I'll make the legs and shaft children of the seat, and then the wheel and feet children of the shaft, and the legs aimed at the feet. What I'd like to do is animate the wheel and have the legs automatically stretch to where they'd need to be for any given angle.
It's not doing that because the IK doesn't work in GameMaker. So that means that I have to tediously hand position the legs on each key frame, and make enough key frames so that the tweened leg motion closely enough matches the tweened wheel motion. You can kind of see in the GIF above how the ankles fall out of socket on a lot of the frames.
It moves fast and is out of focus during gameplay, so that animation is good enough for now, but IK would have made it a lot simpler.