collision system in cocos2dx using spine

nevergiveup

Hello!
I'm new to cocos2dx with spine and try to make a collision system in cocos2dx using bounding box of spine.
But I'm having trouble detectioning.
I have a question about source code around bounding box of spine of cocos2dx.

SkeletonBounds.c

int spPolygon_containsPoint (spPolygon* self, float x, float y) {
   int prevIndex = self->count - 2;
   int inside = 0;
   int i;
   for (i = 0; i < self->count; i += 2) {
      float vertexY = self->vertices[i + 1];
      float prevY = self->vertices[prevIndex + 1];
      if ((vertexY < y && prevY >= y) || (prevY < y && vertexY >= y)) {
         float vertexX = self->vertices[i];
         if (vertexX + (y - vertexY) / (prevY - vertexY) * (self->vertices[prevIndex] - vertexX) < x) inside = !inside;
      }
      prevIndex = i;
   }
   return inside;
}

I have a question about the following process of the above source code

if (vertexX + (y - vertexY) / (prevY - vertexY) * (self->vertices[prevIndex] - vertexX) < x)

I do not understand what this judgement formula is doing.
What this judgement formula is doing?

Mario

The algorithm of this function is pretty simple. It runs through all the polygon edges, and checks which side of an edge a point is on. If a point is on the same side of all edges (which are all given in counter- or clockwise order), then we know the point is inside the concave polygon.

I guess your troubles comes from the fact that you are passing mouse coordinates directly into the function. What you want to do is subtract the skeleton's position from your mouse coordinates, so everything is in the same coordinate system.