trace-iterator to work with unit subsets

src/mol-repr/structure/visual/util/polymer/trace-iterator.ts

@@ -222,9 +222,9 @@ export class AtomicPolymerTraceIterator implements Iterator<PolymerTraceElement>
             const residueIndexNext2 = this.getResidueIndex(residueIndex + 2)
             const residueIndexNext3 = this.getResidueIndex(residueIndex + 3)
 
-            if (value.first) {
             value.centerPrev.element = this.traceElementIndex[residueIndexPrev1]
             value.center.element = this.traceElementIndex[residueIndex]
+            value.centerNext.element = this.traceElementIndex[residueIndexNext1]
 
             this.pos(this.p0, this.traceElementIndex[residueIndexPrev3])
             this.pos(this.p1, this.traceElementIndex[residueIndexPrev2])
@@ -232,27 +232,11 @@ export class AtomicPolymerTraceIterator implements Iterator<PolymerTraceElement>
             this.pos(this.p3, this.traceElementIndex[residueIndex])
             this.pos(this.p4, this.traceElementIndex[residueIndexNext1])
             this.pos(this.p5, this.traceElementIndex[residueIndexNext2])
+            this.pos(this.p6, this.traceElementIndex[residueIndexNext3])
 
             this.setFromToVector(this.d01, residueIndexPrev1)
             this.setFromToVector(this.d12, residueIndex)
             this.setFromToVector(this.d23, residueIndexNext1)
-            } else {
-                value.centerPrev.element = value.center.element
-                value.center.element = value.centerNext.element
-
-                Vec3.copy(this.p0, this.p1)
-                Vec3.copy(this.p1, this.p2)
-                Vec3.copy(this.p2, this.p3)
-                Vec3.copy(this.p3, this.p4)
-                Vec3.copy(this.p4, this.p5)
-                Vec3.copy(this.p5, this.p6)
-
-                Vec3.copy(this.d01, this.d12)
-                Vec3.copy(this.d12, this.d23)
-                Vec3.copy(this.d23, this.d34)
-            }
-            value.centerNext.element = this.traceElementIndex[residueIndexNext1]
-            this.pos(this.p6, this.traceElementIndex[residueIndexNext3])
             this.setFromToVector(this.d34, residueIndexNext2)
 
             this.setControlPoint(value.p0, this.p0, this.p1, this.p2, residueIndexPrev2)