Local bone origin?

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Socoder -> On Topic -> Local bone origin?
Fri, 03 Feb 2012, 15:19
Afr0	So, with the risk of being labeled a psychopath, since I'm worried about this on my birthday, I'm going to post this here because I'm afraid I need some help. How do I find or calculate the local origin of a bone? According to the developer who's been guiding me on how to render a bodymesh, I need to (referring to the vertices) "rotate them around the local bone origin first, then translate the result to the global bone origin coordinate." Translating to the global origin is easy, cos each bone has a global origin. To get the local one, do I have to calculate it manually? Here's my code so far: /// <summary> /// Performs a magic incantation that is neccessary in order to render body meshes. /// </summary> /// <param name="Skel">The skeleton to be used for performing the incantation.</param> public void TransformVerticies(Skeleton Skel, bool Local) { int BoneCount = m_BndCount; int BoundCount = m_NumTexVerticies; int NumTranslations = Skel.GetTranslations().Length; int VertexCounter = 0; Vector3[] Translations = GetVertsAsVector3(Skel, NumTranslations); for (int BoneIndex = 0; BoneIndex < BoneCount; BoneIndex++) { BoneBinding Binding = m_BoneBindings[BoneIndex]; //If local, no bone is used. Bone Bne = Local ? null : Skel.Bones[Binding.BoneIndex]; int VertexCount = 0; VertexPositionNormalTexture[] Verts = GetVerts(); VertexPositionNormalTexture InVec = new VertexPositionNormalTexture(); VertexPositionNormalTexture OutVec = new VertexPositionNormalTexture(); Vector3 GlobalTranslation = (Bne != null) ? Bne.GlobalTranslation : new Vector3(0, 0, 0); Quaternion GlobalRotation = (Bne != null) ? Bne.GlobalRotation : new Quaternion(0, 0, 0, 0); // Phase 0: transform bound vertices. // Phase 1: transform blended vertices. for (int Phase = 0; Phase <= 1; Phase++) { switch (Phase) { case 0: // Set up to transform bound vertices. VertexCount = Binding.VertexCount; if (VertexCount > 0) { InVec.Position = Translations[Binding.FirstVertex]; OutVec = Verts[Binding.FirstVertex]; } break; case 1: // Set up to transform blended vertices. VertexCount = Binding.BlendedVertexCount; if (VertexCount > 0) { InVec.Position = Translations[Binding.FirstBlendedVert + BoundCount]; OutVec = Verts[Binding.FirstBlendedVert + BoundCount]; } break; } //switch int i = 0; // Transform a chunk of bound or blended NormalVertex's. for (i = 0; i < VertexCount + m_BlendCount; i++) { OutVec.Position = Vector3.Transform(InVec.Position, GlobalRotation); OutVec.Normal = Vector3.Transform(InVec.Position, GlobalRotation); OutVec.Position = Vector3.Transform(OutVec.Position, Matrix.CreateTranslation(GlobalTranslation)); //Normals aren't translated! InVec.Position = Translations[i]; OutVec = Verts[i]; } VertexCounter += i / BoneCount; m_Vertices[VertexCounter, 0] = OutVec.Position.X; m_Vertices[VertexCounter, 1] = OutVec.Position.Y; m_Vertices[VertexCounter, 2] = OutVec.Position.Z; m_Vertices[VertexCounter, 3] = OutVec.Normal.X; m_Vertices[VertexCounter, 4] = OutVec.Normal.Y; m_Vertices[VertexCounter, 5] = OutVec.Normal.Z; } } } --v using System; using System.Collections.Generic; using System.Text; using System.IO; using Microsoft.Xna.Framework; namespace XNAWinForms { class Bone { public int ID; //This is assigned when reading a skeleton, to make it easier to look up bones. public string BoneName; public string ParentName; public byte HasSpecialSettings; public uint SettingsCount; //Always 1. public string Setting, Value; //Little Endian! public float[] Translations; public float[] Quaternions; //Back to Big Endian (Maxis...!) public uint CanTranslate; public uint CanRotate; public uint CanUseBlending; public uint CanWiggle; public uint WiggleAmount; public float[,] m_BlendedVertices; public float[,] BlendedVertices { get { return m_BlendedVertices; } set { m_BlendedVertices = value; } } /// <summary> /// The global translation of this bone. /// </summary> public Vector3 GlobalTranslation { get { return new Vector3(Translations[0], Translations[1], Translations[2]); } } /// <summary> /// The global rotation of this bone. /// </summary> public Quaternion GlobalRotation { get { return new Quaternion(Quaternions[0], Quaternions[1], Quaternions[2], Quaternions[3]); } } } class Skeleton { private uint m_Version; private string m_Name; private byte m_BoneCount; private List<Bone> m_Bones = new List<Bone>(); /// <summary> /// The bones in this skeleton. /// </summary> public List<Bone> Bones { get { return m_Bones; } } /// <summary> /// Gets all the rotations for all the bones in this skeleton. /// </summary> /// <returns>An array of quaternions containing rotations.</returns> public Vector3[] GetTranslations() { Vector3[] Translations = new Vector3[m_BoneCount]; for (int i = 0; i < m_Bones.Count; i++) Translations[i] = Bones[i].GlobalTranslation; return Translations; } public Skeleton(byte[] FileData) { MemoryStream MemStream = new MemoryStream(FileData); BinaryReader Reader = new BinaryReader(MemStream); byte NameLen; char[] Name; m_Version = Endian.SwapUInt32(Reader.ReadUInt32()); NameLen = Reader.ReadByte(); Name = Reader.ReadChars(NameLen); m_Name = new string(Name); Reader.ReadByte(); //0... typical useless Maxis value... m_BoneCount = Reader.ReadByte(); for (int i = 0; i < m_BoneCount; i++) { Reader.ReadUInt32(); //1 in hexadecimal... typical useless Maxis value... Bone Bne = new Bone(); Bne.ID = i; NameLen = Reader.ReadByte(); Name = Reader.ReadChars(NameLen); Bne.BoneName = new string(Name); NameLen = Reader.ReadByte(); Name = Reader.ReadChars(NameLen); Bne.ParentName = new string(Name); Bne.HasSpecialSettings = Reader.ReadByte(); if (Bne.HasSpecialSettings == 1) { Reader.ReadUInt32(); //1 in hexadecimal... typical useless Maxis value... //This evaluates to 1000000 in Hex, but should be interpreted as 1. ReadHexUInt(Reader, true); byte SettingLen = Reader.ReadByte(); Bne.Setting = new string(Reader.ReadChars(SettingLen)); byte ValueLen = Reader.ReadByte(); Bne.Value = new string(Reader.ReadChars(ValueLen)); } //Little Endian Bne.Translations = new float[3]; Bne.Translations[0] = Reader.ReadSingle(); Bne.Translations[1] = Reader.ReadSingle(); Bne.Translations[2] = Reader.ReadSingle(); Bne.Quaternions = new float[4]; Bne.Quaternions[0] = Reader.ReadSingle(); Bne.Quaternions[1] = Reader.ReadSingle(); Bne.Quaternions[2] = Reader.ReadSingle(); Bne.Quaternions[3] = Reader.ReadSingle(); //Back to Big Endian and hexadecimal (which genious came up with this shit?!) Bne.CanTranslate = ReadHexUInt(Reader, true); Bne.CanRotate = ReadHexUInt(Reader, true); Bne.CanUseBlending = ReadHexUInt(Reader, true); Bne.CanWiggle = ReadHexUInt(Reader, true); Bne.WiggleAmount = ReadHexUInt(Reader, true); m_Bones.Add(Bne); } } /// <summary> /// Reads a uint (DWORD) from the skeleton file as hexadecimal, /// converts it to a uint and returns it. /// </summary> /// <param name="Reader">The BinaryReader used to read from the skeleton file.</param> /// <param name="BigEndian">Is the value encoded as Big or Small endian?</param> /// <returns>The hexadecimal value as a uint (DWORD).</returns> private uint ReadHexUInt(BinaryReader Reader, bool BigEndian) { if (BigEndian) { string Hex = Endian.SwapUInt32(Reader.ReadUInt32()).ToString("X"); return uint.Parse(Hex); } else { string Hex = Reader.ReadUInt32().ToString("X"); return uint.Parse(Hex); } } } } --v -=-=- Afr0 Games Project Dollhouse on Github - Please fork!
Fri, 03 Feb 2012, 17:27
CodersRule	Afr0, it's okay. That's not why we think you're a psychopath.
Sat, 04 Feb 2012, 06:21
Afr0	I could say the same thing to you.
Sun, 05 Feb 2012, 07:26
CodersRule	I'm sure that anyone who knows me well could.
Sun, 05 Feb 2012, 08:31
steve_ancell	An answer to this topic still hasn't been found, somebody throw Afr0 a frickin' bone here!. Pun intended LMAO!. Ducks once again, in fear of flying rotten vegetables.
Sun, 05 Feb 2012, 12:54
HoboBen	If I'm understanding you right, you have * global position of any bone * the local positions (relative to a given bone) of vertices Assuming bones can't scale (if they do, this adds an extra step) what you do is * first conceptually consider the bone as being at 0,0,0 with a rotation of 0,0,0 * conceptually the vertices local offsets are now global offsets. * conceptually rotate the bone to it's original orientation * to match, the vertices must be rotated relative to 0,0,0 using trigonometry: For the original point: For a translated point: Rearrange to solve x: * Then, conceptually translate the bone from 0,0,0 to it's original position * Do the same for vertices (i.e. just add the bone's global position). Note: you can probably do this more efficiently with matrices (especially in 3D), but I haven't covered that yet! -=-=- blog \| work \| code \| more code
Mon, 06 Feb 2012, 05:16
Afr0	o_O Any way you could translate that from math to pseudocode? -=-=- Afr0 Games Project Dollhouse on Github - Please fork!