How to calculate the weights of the nodes in a 2d blend space ?

ostef · 2021-03-05T12:41:28

Hi! I've been working on an animation system to gain some experience, and I want to implement 2d blend spaces. Here's the struct of a 2d blend space: Blend_Space_2d :: struct { Node :: struct { clip : *Asset (Animation_Clip); position : Vec2; } skeleton : *Asset (Skeleton); nodes : [..]Node; } I am currently stuck trying to calculate the influences of each node in the blend space. I took a look at Unity's blend trees, and it seems that only at most the 3 closest nodes to the input position can influence the final pose. So right now I sort an array of nodes based on their distance to the input position, how do I calculate the influences of each of the three closest nodes. I have already identified some special cases: When the closest node's distance to the input position is 0, its influence is 1 and the two other nodes have an influence of 0 (don't forget the influences must add up to 1), When the 3 nodes are equidistant to ‘position’, all nodes have the same influence of ⅓, When ‘position’ lies on the edge formed by nodes A and B, node C has an influence of 0 and it is trivial to then calculate the influences of node A and B (influence = 1 - distance to position / distance between A and B) It seems obvious that the influence of a node is function of its distance to the input position, but I'm having a hard time figuring out what this function is. Any ideas ?

Math and Physics Programming Animation BlendTree blendspace engine

Started by ostef March 04, 2021 02:00 PM

10 comments, last by ostef 3 years, 11 months ago

ostef

Author

March 05, 2021 12:41 PM

Gradient band interpolation is the way to go! It's not even hard to implement (https://www.shadertoy.com/view/XlKXWR). Here's a little gif of a blend space I will use to apply additive leaning (using polar space gradient band interpolation, in Unity this would be "2D Freeform Directional").

How to calculate the weights of the nodes in a 2d blend space ?

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How to calculate the weights of the nodes in a 2d blend space ?

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