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  • understanding and implementing Boids

    - by alphablender
    So I'm working on porting Boids to Brightscript, based on the pseudocode here: http://www.kfish.org/boids/pseudocode.html I'm trying to understand the data structures involved, for example is Velocity a single value, or is it a 3D value, ie velocity={x,y,z} It seems as if the pseudocode seems to mix this up where sometimes it has an equation that incudes both vectors and single-value items: v1 = rule1(b) v2 = rule2(b) v3 = rule3(b) b.velocity = b.velocity + v1 + v2 + v3 If Velocity is a tripartite value then this would make sense, but I'm not sure. So my first question here is, is this the correct datastructure for a single boid based on the Pseudocode on that page: boid={position:{px:0,py:0,pz:0},velocity:{x:0,y:0,z:0},vector:{x:0,y:0,z:0},pc:{x:0,y:0,z:0},pv:{x:0,y:0,z:0}) where pc=perceived center, pv= perceived velocity I"ve implemented a vector_add, vector_sub, vector_div, and vector boolean functions. The reason I'm starting from this pseudocode is I've not been able to find anything else that is as readable, but it still leaves me with lots of questions as the data structures are not explicitly defined for each variable. (edit) here's a good example of what i'm talking about: IF |b.position - bJ.position| < 100 THEN if b.position - b[j].position are both 3D coordinates, how can they be considered "less than 100" unless they are < {100,100,100} ? Maybe that is what I need to do here, use a vector comparison function?

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  • XNA- Transforming children

    - by user1806687
    So, I have a Model stored in MyModel, that is made from three meshes. If you loop thrue MyModel.Meshes the first two are children of the third one. And was just wondering, if anyone could tell me where is the problem with my code. This method is called whenever I want to programmaticly change the position of a whole model: public void ChangePosition(Vector3 newPos) { Position = newPos; MyModel.Root.Transform = Matrix.CreateScale(VectorMathHelper.VectorMath(CurrentSize, DefaultSize, '/')) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Up, MathHelper.ToRadians(Rotation.Y)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Right, MathHelper.ToRadians(Rotation.X)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Forward, MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(Position); Matrix[] transforms = new Matrix[MyModel.Bones.Count]; MyModel.CopyAbsoluteBoneTransformsTo(transforms); int count = transforms.Length - 1; foreach (ModelMesh mesh in MyModel.Meshes) { mesh.ParentBone.Transform = transforms[count]; count--; } } This is the draw method: foreach (ModelMesh mesh in MyModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.View = camera.view; effect.Projection = camera.projection; effect.World = mesh.ParentBone.Transform; effect.EnableDefaultLighting(); } mesh.Draw(); } The thing is when I call ChangePosition() the first time everything works perfectlly, but as soon as I call it again and again. The first two meshes(children meshes) start to move away from the parent mesh. Another thing I wanted to ask, if I change the scale/rotation/position of a children mesh, and then do CopyAbsoluteBoneTransforms() will children meshes be positioned properlly(at the proper distance) or would achieving that require more math/methods? Thanks in advance

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