more work on the twist problem

modules/gfx/src/impl/entity_detail.cc

@@ -304,6 +304,102 @@ SplineEntryList Spline::Generate(const SplineEntryList& entry_list, int nsub, ui
   SPLINE_ENTRY_INTERPOLATE(rad);
 
   LOG_DEBUG("SplineGenerate: assigning direction and normal components");
+
+#if 0
+  std::vector<Quat> quats(size+3);
+
+  Vec3 prevn;
+  for(int c=0;c<size;++c) {
+    Vec3 d1,d2;
+    if(c==0) {
+      d1=Normalize(entry_list.at(c).position-entry_list.at(c+1).position);
+      d2=Normalize(entry_list.at(c+1).position-entry_list.at(c+2).position);
+    } else if(c==size-1) {
+      d1=Normalize(entry_list.at(c-2).position-entry_list.at(c-1).position);
+      d2=Normalize(entry_list.at(c-1).position-entry_list.at(c).position);
+    } else {
+      d1=Normalize(entry_list.at(c-1).position-entry_list.at(c).position);
+      d2=Normalize(entry_list.at(c).position-entry_list.at(c+1).position);
+    }
+    Vec3 d=d2;
+    Vec3 n=Normalize(Cross(d1,d2));
+    //Vec3 n=entry_list.at(c).v1;
+    Vec3 o = Normalize(Cross(d,n));
+
+    if(c>0) {
+      if(Dot(Normalize(Cross(d,prevn)),Normalize(Cross(d,n)))<0.0) {
+        n=-n;
+        o=-o;
+      }
+    }
+    prevn=n;
+
+    //n = Normalize(Cross(o,d));
+    Quat q(Mat3(d[0],n[0],o[0],
+                d[1],n[1],o[1],
+                d[2],n[2],o[2]));
+    quats[c+1]=q;
+  }
+  quats.at(0)=quats.at(1);
+  quats.at(size)=quats.at(size-1);
+  quats.at(size+1)=quats.at(size-1);
+  
+  std::vector<Quat> squats(size*nsub);
+  // now for the quaternion interpolation, using squad
+  for(int c=0;c<size;++c) {
+    Quat q0=quats.at(c+0);
+    Quat q1=quats.at(c+1);
+    Quat q2=quats.at(c+2);
+    Quat q3=quats.at(c+3);
+
+    Quat s1=q1*Exp(-0.25*Log(Inv(q1)*q2)+Log(Inv(q1)*q0));
+    Quat s2=q2*Exp(-0.25*Log(Inv(q2)*q3)+Log(Inv(q2)*q1));
+
+    for(int d=0;d<nsub;++d) {
+      float u=static_cast<float>(d)*i_nsub;
+      squats.at(c*nsub+d) = Slerp(Slerp(q1,q2,u),Slerp(s1,s2,u),2.0*u*(1.0-u));
+    }
+  }
+
+  assert(sublist.size()<=squats.size());
+
+  for(unsigned int i=0;i<sublist.size();++i) {
+    Mat3 m=squats[i].ToRotationMatrix();
+    sublist.at(i).direction=Normalize(Vec3(m(0,0),m(1,0),m(2,0)));
+    sublist.at(i).normal=Normalize(Vec3(m(0,1),m(1,1),m(2,1)));
+    sublist.at(i).v2=Normalize(Vec3(m(0,2),m(1,2),m(2,2)));
+  }
+
+  std::vector<Vec3> nlist(sublist.size());
+  for(uint i=0;i<sublist.size();++i) {
+    Vec3 p0,p1;
+    if(i<sublist.size()-1) {
+      p0 = sublist.at(i).position;
+      p1 = sublist.at(i+1).position;
+    } else {
+      p0 = sublist.at(i-1).position;
+      p1 = sublist.at(i).position;
+    }
+    sublist.at(i).direction=Normalize(p1-p0);
+    Vec3 orth = Normalize(Cross(sublist.at(i).direction,sublist.at(i).normal));
+    nlist[i] = Normalize(Cross(orth,sublist.at(i).direction));
+    sublist.at(i).v2=orth;
+    if(i>0) {
+      if(Dot(Normalize(Cross(sublist.at(i).direction,nlist[i-1])),orth)<0.0) {
+        nlist[i]=-nlist[i];
+        sublist.at(i).v2=-sublist.at(i).v2;
+      }
+    }
+  }
+
+  sublist.at(0).normal=nlist[0];
+  sublist.back().normal=nlist.back();
+  for(uint i=1;i<sublist.size()-1;++i) {
+    sublist.at(i).normal=Normalize((nlist[i-1]+nlist[i]+nlist[i+1])/3.0);   
+  }
+
+#else
+
   // assign direction and normal
   // entity trace has the same algorithm
 
@@ -367,6 +463,8 @@ SplineEntryList Spline::Generate(const SplineEntryList& entry_list, int nsub, ui
     sublist.at(i).normal = sublist.at(i).v0;
   }
 
+#endif
+
   LOG_DEBUG("SplineGenerate: assigning non-interpolated entry components");
   // finally the non-interpolated type
   // with some tweaks for proper strand rendering

modules/gfx/src/impl/sline_renderer.cc

@@ -83,7 +83,7 @@ void SlineRenderer::PrepareRendering(const BackboneTrace& trace_subset,
         VertexID p1 = va.Add(sit->position, geom::Vec3(),sit->color1);
         va.AddLine(p0,p1);
         p0=p1;
-#if 0
+#if 1
         VertexID p2 = va.Add(sit->position+sit->direction,geom::Vec3(),Color(0,1,0));
         VertexID p3 = va.Add(sit->position+sit->normal,geom::Vec3(),Color(1,0,0));
         VertexID p4 = va.Add(sit->position+sit->v2,geom::Vec3(),Color(1,0,1));