Question

我正在尝试为c＃编写.bvh动画导出器，并使用Blender的这个export_bvh.py脚本作为示例进行复制。

我的Unity导出器脚本基本上在场景处于活动状态时每帧存储骨骼的旋转。场景停止后，然后将该euler旋转列表保存到.bvh文件中。

我设法让文件的标题部分看起来不错，但我现在无法计算骨骼的角度。

根据我的理解，它们是通过将父母的全局变换矩阵乘以子变换矩阵和静止位置矩阵来复合角度。但细节对我来说并不是很清楚。

所以我尽力检查并复制了export_bvh.py脚本中矩阵乘法的方式，即使我觉得我已经取得了一些进展，但我仍然面临一个从一开始就存在的问题在导入我录制的动画后，轮换有时会偏离，有时则不然。我相信（但不确定）是由于Blender是右撇子而Unity是左撇子坐标系。

例如，当我启动Unity场景并开始录制动画时，我会移动我的骨架中的一些骨骼（记录下来），然后在保存动画后我尝试将.bvh导入Blender 。在检查动画之后，我注意到当一个骨骼沿着多个轴旋转时，它会在动画中产生奇怪的结果，并且一些旋转要么四处晃动，要么看起来剧烈摇晃。但通常沿单轴旋转时，它似乎朝正确的方向移动。

我创建了这个视频，更好地解释了这个问题并展示了一些例子： Video thumbnail
MORE DETAILS on YouTube

以下是此项目的完整脚本：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SimpleBVH5 : MonoBehaviour {

    string bvhOutput;
    public string savePath = "C:\\animations\\animation.bvh";
    public int fps = 60;

    Quaternion rootRotationOffset;

    //ARMATURE BONES SECTION
    public Transform hip;
    public Transform spine;
    public Transform chest;

    public Transform shoulderR;
    public Transform upper_armR;

    public class DecoratedBone {
        public Transform bone;
        public DecoratedBone parent; // decorated bone parent, set in a later loop
        public Vector3 rest_bone_head; // blender armature bone head position
        public Matrix4x4 rest_arm_mat; // blender rest matrix (armature space)
        public Matrix4x4 rest_arm_imat; // rest_arm_mat inverted
    }
    List<DecoratedBone> dBones;

    //INITIALIZATION SECTION
    void OnEnable () {
        dBones = new List<DecoratedBone> ();
        rootRotationOffset = hip.rotation;

        int level = 0;

        bvhOutput = "HIERARCHY\n";
        bvhOutput += "ROOT hip\n";

        var dBone = new DecoratedBone ();
        dBone.bone = hip;
        dBone.rest_bone_head = hip.position;

        var rest_arm_mat = GetMatrix (dBone, rootRotationOffset);

        dBone.rest_arm_mat = rest_arm_mat;
        dBone.rest_arm_imat = rest_arm_mat.inverse;

        dBones.Add (dBone);

        bvhOutput += "{\n";
        var offset = hip.position;
        bvhOutput += "\tOFFSET " + offset.x.ToString("F6") + " " + (-offset).z.ToString("F6") + " " + offset.y.ToString("F6") + "\n";
        bvhOutput += "\tCHANNELS 6 Xposition Yposition Zposition Xrotation Yrotation Zrotation\n";

        var spineBone = InsertHierarchy (ref level, "spine", spine, dBone);
        InsertHierarchy (ref level, "chest", chest, spineBone);
        AscendLevel (ref level, chest, chest.GetChild (0), 1);
        var shoulderRBone = InsertHierarchy (ref level, "shoulder.R", shoulderR, spineBone);
        InsertHierarchy (ref level, "upper_arm.R", upper_armR, shoulderRBone);
        AscendLevel (ref level, upper_armR, upper_armR.GetChild (0));

        bvhOutput += "}\n";

        bvhOutput += "MOTION\n";
        bvhOutput += "Frames: 1\n";
        bvhOutput += "Frame Time:\t" + (1.0f / fps).ToString("F6") + "\n";

        StartCoroutine (RecordRoutine ()); // Finished building header info, Begin recording keyframes
    }

    void OnDestroy() {
        System.IO.File.WriteAllText(savePath, bvhOutput);
        print ("SAVED FILE!!!");
    }

    // HEADER SECTION HELPERS
    DecoratedBone InsertHierarchy(ref int level, string name, Transform bone, DecoratedBone parent) {
        /* Creats hierarchy header info for bones with parents */
        string tabs = GetLevelTabs(level);
        bvhOutput += tabs + "JOINT "+name+"\n";
        bvhOutput += tabs + "{\n";
            var dBone = new DecoratedBone ();
            dBone.bone = bone;
            dBone.parent = parent;

            dBone.rest_bone_head = bone.position;
            var rest_arm_mat = GetMatrix (dBone, rootRotationOffset);

            dBone.rest_arm_mat = rest_arm_mat;
            dBone.rest_arm_imat = rest_arm_mat.inverse;
            dBones.Add (dBone); // Add bone to the list of bones (in the order it was created in the hiereachy/header).

            var offset = bone.position - parent.bone.position;
            bvhOutput += tabs + "\tOFFSET " + offset.x.ToString("F6") + " " + (-offset).z.ToString("F6") + " " + offset.y.ToString("F6") + "\n";
            bvhOutput += tabs + "\tCHANNELS 3 Xrotation Yrotation Zrotation\n";
        level++; // Increase the level in the hierarchy (increases depth in .bvh file and ensures curly braces will be added properly)

        Debug.DrawLine (parent.bone.position, bone.position, Color.cyan, 10.0f); // Outline the skeleton in the viewport for debugging
        return dBone;
    }

    string GetLevelTabs(int level) {
        string tabs = "";
        for (int lev = 0; lev <= level; lev++) {
            tabs += "\t";
        }
        return tabs;
    }

    void EndSite(int level, Transform bone, Transform endEffector) {
        string tabs = GetLevelTabs(level);
        bvhOutput += tabs + "End Site\n";
        bvhOutput += tabs + "{\n";
        var offset = endEffector.position - bone.position;
        bvhOutput += tabs + "\tOFFSET " + offset.x.ToString("F6") + " " + (-offset).z.ToString("F6") + " " + offset.y.ToString("F6") + "\n"; // 1 0 0\n";
        bvhOutput += tabs + "}\n";

        Debug.DrawRay (bone.position, offset, Color.cyan, 10.0f);
    }

    void AscendLevel (ref int level, Transform bone, Transform endEffector, int stopLevel = 0) {
        EndSite (level, bone, endEffector);

        for (int lev = level; lev > stopLevel; lev--) {
            for (int tab = 0; tab < lev; tab++) {
                bvhOutput += "\t";
            }
            bvhOutput += "}\n";
        }
        level = stopLevel;
    }


    //RECORDED MOTION SECTION
    IEnumerator RecordRoutine () {
        /*A simplified re-write of Blender's export_bvh.py script https://github.com/sftd/blender-addons/blob/master/io_anim_bvh/export_bvh.py*/
        string line; // The string used to build each line of data.
        float time = Time.time;
        float interval = 1.0f / fps; // The record frame interval.
        while (isActiveAndEnabled) { // Runs while the scene is actively running.
            yield return new WaitUntil (() => (Time.time - time) >= interval); // Wait for desired time interval.
            time = Time.time; // Reset the timer.
            yield return new WaitForEndOfFrame (); // Wait for all transforms to be updated.

            line = ""; // Clear the line data and prepare for next line of data.

            //First do calculations for the root (hip) bone.
            var p = dBones[0].rest_bone_head;
            var trans = Matrix4x4.Translate (p);
            var itrans = Matrix4x4.Translate (-p);

            var pose_mat = GetMatrix(dBones [0], rootRotationOffset);
            var rest_arm_imat = dBones [0].rest_arm_imat;

            var mat_final = pose_mat * rest_arm_imat;
            mat_final = itrans * mat_final * trans;

            var loc = mat_final.GetPosition () ;
            var rot = mat_final.GetRotation ().eulerAngles;
            line += // Add root's (hip bone) data to the line of data.
                (-loc.x).ToString("F6") + " " + //Output location of root bone
                (-loc.z).ToString("F6") + " " +
                (loc.y).ToString("F6") + " " +

                (rot.x).ToString("F6") + " " + //Output rotation of root bone
                (rot.z).ToString("F6") + " " +
                (-rot.y).ToString("F6") + " ";      

            // Now do calculations for each child bone
            for (int i = 1; i < dBones.Count; i++) { 

                p = dBones [i].rest_bone_head;
                trans = Matrix4x4.Translate (p);
                itrans = Matrix4x4.Translate (-p);

                mat_final = 
                    dBones [i].parent.rest_arm_mat * GetMatrix(dBones [i].parent).inverse *
                    GetMatrix(dBones [i]) * dBones [i].rest_arm_imat;
                mat_final = itrans * mat_final * trans;

                //loc = mat_final.GetPosition () + (trackedObjects [i].rest_bone_head - trackedObjects [i].parent.rest_bone_head); //Position is not required for non-root bones
                rot = mat_final.GetRotation ().eulerAngles;

                line += // Add children's data to the line of data.
                    (rot.x).ToString("F6") + " " + //Output rotation of child bone
                    (rot.z).ToString("F6") + " " +
                    (-rot.y).ToString("F6") + " ";
            }
            line += "\n"; // Done adding line.

            if (Application.isPlaying) {
                bvhOutput += line; // Add the data to the file's contents only if the scene is actively running.
            }

        }
    }

    Matrix4x4 GetMatrix (DecoratedBone dBone, Quaternion offsetRotation = default(Quaternion)) {
        //return trackedObject.obj.localToWorldMatrix;
        return Matrix4x4.TRS(
            dBone.bone.position,
            offsetRotation.Equals(default(Quaternion)) ? dBone.bone.rotation : dBone.bone.rotation * offsetRotation, //the offsetRotation (aka hip.rotation) should be applied to all bones with parents.
            Vector3.one
        );
    }
}

感谢任何可以提供帮助的人！

在坐标系之间转换导致旋转/万向节问题！需要帮助

0 个答案: