Fix bone direction parallel with y axis.

README.md

@@ -53,6 +53,9 @@ I created the test nodes's geometry information from Blender. Here is the render
 *Generate Mesh*  
 <img src="screenshot/dust3d_generate_quad.png" width="124" height="128">  
 When I am implementing the B-Mesh algorithm, I am also think in the future, how to create a library of bunch of initial base models. There is a paper [the Skeleton of a Closed 3D Shape](http://www1.idc.ac.il/icgf/GraphicsSeminar2006/DCGskeleton06.pdf) described how to generate skeleton from mesh, this is the reverse progress of what I am doing, I think it can resolve the problem of insufficient initial base models, I can generate from tons of existed models.  
+*Convex Hull*  
+After finish the rotation at the two connected bones, I need implement [3D Convex Hull](https://en.wikipedia.org/wiki/Convex_hull) algorithm at joint ball.
+
 - [ ] Export Wavefront .obj  
 - [ ] Render B-Mesh result  
 - [ ] Design UI for monster parts configuration  

data/bmesh_test_1.h

@@ -3,10 +3,12 @@ const float bmeshTest1Balls[][6] = {
       {2, -0.91403, 0.77069, 0.62299, 0.5},            {3, 2.25224, 0.74973, 0.85115, 0.5},
                                     {4, 0, 0, 0, 0.8, 1},
                                {5, 0.00920, -0.66115, -2.04601, 0.5},
-                               {6, 0.01726, -0.88224, -2.87471, 0.2}
+                               {6, 0.01726, -0.88224, -2.87471, 0.2},
+                               {7, 0, -2, 0.00, 0.2},
+                               {8, -0.3, -2.8, 0.13, 0.5},
 };
 
 const int bmeshTest1Bones[][2] = {
   {0, 2}, {2, 4}, {4, 3}, {3, 1},
-  {4, 5}, {5, 6}
+  {4, 5}, {5, 6}, {4, 7}, {7, 8}
 };

src/bmesh.c

@@ -205,6 +205,20 @@ static int bmeshGenerateBallCrossSection(bmesh *bm, bmeshBall *ball,
   return 0;
 }*/
 
+static void generateYZfromBoneDirection(vec3 *boneDirection,
+    vec3 *localYaxis, vec3 *localZaxis) {
+  vec3 worldYaxis = {0, 1, 0};
+  vec3 worldXaxis = {1, 0, 0};
+  if (0 == vec3Angle(boneDirection, &worldYaxis)) {
+    vec3CrossProduct(&worldXaxis, boneDirection, localYaxis);
+  } else {
+    vec3CrossProduct(&worldYaxis, boneDirection, localYaxis);
+  }
+  vec3Normalize(localYaxis);
+  vec3CrossProduct(localYaxis, boneDirection, localZaxis);
+  vec3Normalize(localZaxis);
+}
+
 static int bmeshGenerateInbetweenBallsBetween(bmesh *bm,
       int firstBallIndex, int secondBallIndex) {
   float step;
@@ -215,6 +229,7 @@ static int bmeshGenerateInbetweenBallsBetween(bmesh *bm,
   vec3 boneDirection;
   vec3 normalizedBoneDirection;
   vec3 worldYaxis = {0, 1, 0};
+  vec3 worldXaxis = {1, 0, 0};
   bmeshBall *firstBall = bmeshGetBall(bm, firstBallIndex);
   bmeshBall *secondBall = bmeshGetBall(bm, secondBallIndex);
   bmeshBall *newBall;
@@ -227,10 +242,20 @@ static int bmeshGenerateInbetweenBallsBetween(bmesh *bm,
   vec3Sub(&firstBall->position, &secondBall->position, &boneDirection);
   normalizedBoneDirection = boneDirection;
   vec3Normalize(&normalizedBoneDirection);
-  vec3CrossProduct(&worldYaxis, &boneDirection, &localYaxis);
+  generateYZfromBoneDirection(&boneDirection,
-  vec3Normalize(&localYaxis);
+    &localYaxis, &localZaxis);
-  vec3CrossProduct(&localYaxis, &boneDirection, &localZaxis);
+  
-  vec3Normalize(&localZaxis);
+  glColor3f(0.0, 0.0, 0.0);
+  drawDebugPrintf("<%f,%f,%f> <%f,%f,%f> <%f,%f,%f>",
+    localYaxis.x,
+    localYaxis.y,
+    localYaxis.z,
+    localZaxis.x,
+    localZaxis.y,
+    localZaxis.z,
+    boneDirection.x,
+    boneDirection.y,
+    boneDirection.z);
 
   distance = vec3Length(&boneDirection);
   if (distance > BMESH_STEP_DISTANCE) {
@@ -425,11 +450,8 @@ static int bmeshSweepFrom(bmesh *bm, bmeshBall *parent, bmeshBall *ball) {
         ball->boneDirection = parent->boneDirection;
         vec3RotateAlong(&ball->boneDirection, rotateAngle, &rotateAxis,
           &ball->boneDirection);
-        vec3CrossProduct(&worldYaxis, &ball->boneDirection, &ball->localYaxis);
+        generateYZfromBoneDirection(&ball->boneDirection,
-        vec3Normalize(&ball->localYaxis);
+          &ball->localYaxis, &ball->localZaxis);
-        vec3CrossProduct(&ball->localYaxis, &ball->boneDirection,
-          &ball->localZaxis);
-        vec3Normalize(&ball->localZaxis);
       } else {
         // TODO:
       }
@@ -470,6 +492,7 @@ static bmeshBall *bmeshFindBallForConvexHull(bmesh *bm, bmeshBall *root,
   if (!child) {
     return ball;
   }
+  ball->radius = 0;
   return bmeshFindBallForConvexHull(bm, root, child);
 }
 

src/render.cpp

@@ -258,6 +258,7 @@ void Render::paintGL() {
 
     bmeshGenerateInbetweenBalls(bm);
     bmeshSweep(bm);
+    bmeshStitch(bm);
   }
 
   drawBmeshBallRecursively(bm, bmeshGetRootBall(bm));