# bearsomg

Member Since 27 Jun 2012
Offline Last Active Aug 27 2012 11:01 PM

### CCD IK is Jerky and sometimes spazzy

27 August 2012 - 11:00 PM

Hello. I am writing an IK solver for a 3D rendering engine that I am designing. My solver works correctly for the most part, but sometimes it will make the animation look jerky or completely spazz out (this usually happens when the joints have to bend over each other more).

This is my solver function: http://pastebin.com/K1UZf0D5

The UpdateIK() function uses this algorithm to update the bone's combined transform:

D3DXMatrixRotationQuaternion(&combTrans, &combRot);
combTrans(3,0) = translate(3,0) + offset.x;
combTrans(3,1) = translate(3,1) + offset.y;
combTrans(3,2) = translate(3,2) + offset.z;
if (_parent)
combTrans *= _parent->getCombinedTrans();



Here is a video example of how the IK will be jerky or spazz out. Look at the left leg. The video is the model's bone structure.

### Indexed Vertex Blending with the Direct3D Pipeline

27 June 2012 - 04:47 PM

Hello. I am currently working on a rendering engine which is meant to render character animations. Right now I am working on vertex blending to make the body parts move with the bones.

For each vertex declaration, I have a short that represents the first bone's weight, and 2 shorts representing which bones the vertex is affected by. These 2 shorts also are indexes to an array of combined transformation matrices (in world space) which represent each bone's transformation in world space.

When the model is loaded from the file, this loop is run for each vertex to build the array of vertices that will be uploaded to the vertex buffer:

for (int i=0;i<(int)_numVertex;i++)
{
cVertices[i].x = vertex[i].pos[0];
cVertices[i].y = vertex[i].pos[1];
cVertices[i].z = vertex[i].pos[2];
cVertices[i].normal.x = vertex[i].normal[0];
cVertices[i].normal.y = vertex[i].normal[1];
cVertices[i].normal.z = vertex[i].normal[2];
cVertices[i].tu = vertex[i].uv[0];
cVertices[i].tv = vertex[i].uv[1];
cVertices[i].su = (float)(vertex[i].normal[0]/2)+0.5;
cVertices[i].sv = (float)(vertex[i].normal[1]/2)+0.5;
_bone1List[i] = vertex[i].boneID[0];
_bone2List[i] = vertex[i].boneID[1];
_boneWeight1[i] = vertex[i].boneWeight1*0.01f;

cVertices[i].b1 = _boneWeight1[i];

cVertices[i].matIndices = ((_bone2List[i] & 0xFF) << 8) | (_bone1List[i] & 0xFF);
}


"b1" is the bone weight, and "matIndices" is the packed DWORD with the matrix palette indices.

For each frame, this loop is then called to update the world transformation matrices palette which contains each bone's combined transformation matrix:

for (int i=0;i<boneController._numBones;i++)
{
}


The problem is, when the model is loaded, the entire character is overly stretched and goes off the top of the screen. Does anyone know why this could be happening?

Here is my FVF declatation:

#define MDLFVF (D3DFVF_XYZB2 | D3DFVF_LASTBETA_UBYTE4 | D3DFVF_NORMAL | D3DFVF_TEX1 | D3DFVF_TEX2)
struct MDLVERTEX
{
FLOAT x, y, z;
FLOAT b1;
DWORD matIndices;
D3DVECTOR normal;
FLOAT tu, tv;
FLOAT su, sv;
};