Merge pull request #520 from MadCatX/clean_up_pyramids

Change the lookup logic of NtC steps from residues

CHANGELOG.md

@@ -10,6 +10,7 @@ Note that since we don't clearly distinguish between a public and private interf
 - Add custom labels to Confal pyramids
 - Improve naming of some internal types in Confal pyramids extension coordinate
 - Add example mmCIF file with categories necessary to display Confal pyramids
+- Change the lookup logic of NtC steps from residues
 
 ## [v3.13.0] - 2022-07-24
 

src/extensions/dnatco/confal-pyramids/property.ts

@@ -16,7 +16,7 @@ import { PropertyWrapper } from '../../../mol-model-props/common/wrapper';
 import { ParamDefinition as PD } from '../../../mol-util/param-definition';
 import { MmcifFormat } from '../../../mol-model-formats/structure/mmcif';
 
-export type ConfalPyramids = PropertyWrapper<CPT.StepsData | undefined>;
+export type ConfalPyramids = PropertyWrapper<CPT.Steps | undefined>;
 
 export namespace ConfalPyramids {
     export const Schema = {
@@ -105,13 +105,13 @@ export const ConfalPyramidsProvider: CustomModelProperty.Provider<ConfalPyramids
 
 type StepsSummaryTable = Table<typeof ConfalPyramids.Schema.ndb_struct_ntc_step_summary>;
 
-function createPyramidsFromCif(model: Model,
+function createPyramidsFromCif(
+    model: Model,
     cifSteps: Table<typeof ConfalPyramids.Schema.ndb_struct_ntc_step>,
-    stepsSummary: StepsSummaryTable): CPT.StepsData {
+    stepsSummary: StepsSummaryTable
+): CPT.Steps {
     const steps = new Array<CPT.Step>();
-    const names = new Map<string, number>();
-    const halfPyramids = new Array<CPT.HalfPyramid>();
-    let hasMultipleModels = false;
+    const mapping = new Array<CPT.MappedChains>();
 
     const {
         id, PDB_model_number, name,
@@ -123,21 +123,24 @@ function createPyramidsFromCif(model: Model,
     if (_rowCount !== stepsSummary._rowCount) throw new Error('Inconsistent mmCIF data');
 
     for (let i = 0; i < _rowCount; i++) {
-        const model_num = PDB_model_number.value(i);
-        if (model_num !== model.modelNum)
-            hasMultipleModels = true;
-
         const {
             NtC,
             confal_score,
             rmsd
         } = getSummaryData(id.value(i), i, stepsSummary);
+        const modelNum = PDB_model_number.value(i);
+        const chainId = auth_asym_id_1.value(i);
+        const seqId = auth_seq_id_1.value(i);
+        const modelIdx = modelNum - 1;
+
+        if (mapping.length <= modelIdx || !mapping[modelIdx])
+            mapping[modelIdx] = new Map<string, CPT.MappedResidues>();
 
         const step = {
-            PDB_model_number: model_num,
+            PDB_model_number: modelNum,
             name: name.value(i),
-            auth_asym_id_1: auth_asym_id_1.value(i),
-            auth_seq_id_1: auth_seq_id_1.value(i),
+            auth_asym_id_1: chainId,
+            auth_seq_id_1: seqId,
             label_comp_id_1: label_comp_id_1.value(i),
             label_alt_id_1: label_alt_id_1.value(i),
             PDB_ins_code_1: PDB_ins_code_1.value(i),
@@ -152,13 +155,18 @@ function createPyramidsFromCif(model: Model,
         };
 
         steps.push(step);
-        names.set(step.name, steps.length - 1);
 
-        halfPyramids.push({ step, isLower: false });
-        halfPyramids.push({ step, isLower: true });
+        const mappedChains = mapping[modelIdx];
+        const residuesOnChain = mappedChains.get(chainId) ?? new Map<number, number[]>();
+        const stepsForResidue = residuesOnChain.get(seqId) ?? [];
+        stepsForResidue.push(steps.length - 1);
+
+        residuesOnChain.set(seqId, stepsForResidue);
+        mappedChains.set(chainId, residuesOnChain);
+        mapping[modelIdx] = mappedChains;
     }
 
-    return { steps, names, halfPyramids, hasMultipleModels };
+    return { steps, mapping };
 }
 
 function getSummaryData(id: number, i: number, stepsSummary: StepsSummaryTable) {

src/extensions/dnatco/confal-pyramids/representation.ts

@@ -6,7 +6,7 @@
  */
 
 import { ConfalPyramids, ConfalPyramidsProvider } from './property';
-import { ConfalPyramidsUtil } from './util';
+import { ConfalPyramidsIterator } from './util';
 import { ConfalPyramidsTypes as CPT } from './types';
 import { Interval } from '../../../mol-data/int';
 import { Mesh } from '../../../mol-geo/geometry/mesh/mesh';
@@ -32,6 +32,12 @@ const t = Mat4.identity();
 const w = Vec3.zero();
 const mp = Vec3.zero();
 
+const posO3 = Vec3();
+const posP = Vec3();
+const posOP1 = Vec3();
+const posOP2 = Vec3();
+const posO5 = Vec3();
+
 function calcMidpoint(mp: Vec3, v: Vec3, w: Vec3) {
     Vec3.sub(mp, v, w);
     Vec3.scale(mp, mp, 0.5);
@@ -53,64 +59,76 @@ function createConfalPyramidsIterator(structureGroup: StructureGroup): LocationI
     const { structure, group } = structureGroup;
     const instanceCount = group.units.length;
 
-    const prop = ConfalPyramidsProvider.get(structure.model).value;
-    if (prop === undefined || prop.data === undefined) {
-        return LocationIterator(0, 1, 1, () => NullLocation);
-    }
+    const data = ConfalPyramidsProvider.get(structure.model)?.value?.data;
+    if (!data) return LocationIterator(0, 1, 1, () => NullLocation);
 
-    const { halfPyramids } = prop.data;
+    const halfPyramidsCount = data.steps.length * 2;
 
     const getLocation = (groupIndex: number, instanceIndex: number) => {
-        if (halfPyramids.length <= groupIndex) return NullLocation;
-        return CPT.Location(halfPyramids[groupIndex]);
+        if (halfPyramidsCount <= groupIndex) return NullLocation;
+        const idx = Math.floor(groupIndex / 2); // Map groupIndex to a step, see createConfalPyramidsMesh() for full explanation
+        return CPT.Location(data.steps[idx], groupIndex % 2 === 1);
     };
-    return LocationIterator(halfPyramids.length, instanceCount, 1, getLocation);
+    return LocationIterator(halfPyramidsCount, instanceCount, 1, getLocation);
 }
 
 function createConfalPyramidsMesh(ctx: VisualContext, unit: Unit, structure: Structure, theme: Theme, props: PD.Values<ConfalPyramidsMeshParams>, mesh?: Mesh) {
     if (!Unit.isAtomic(unit)) return Mesh.createEmpty(mesh);
 
-    const prop = ConfalPyramidsProvider.get(structure.model).value;
-    if (prop === undefined || prop.data === undefined) return Mesh.createEmpty(mesh);
+    const data = ConfalPyramidsProvider.get(structure.model)?.value?.data;
+    if (!data) return Mesh.createEmpty(mesh);
 
-    const { steps } = prop.data;
+    const { steps, mapping } = data;
     if (steps.length === 0) return Mesh.createEmpty(mesh);
-
-    const mb = MeshBuilder.createState(512, 512, mesh);
-
-    const handler = (step: CPT.Step, first: ConfalPyramidsUtil.FirstResidueAtoms, second: ConfalPyramidsUtil.SecondResidueAtoms, firsLocIndex: number, secondLocIndex: number) => {
-        if (firsLocIndex === -1 || secondLocIndex === -1)
-            throw new Error('Invalid location index');
-
-        const scale = (step.confal_score - 20.0) / 100.0;
-        const O3 = first.O3.pos;
-        const OP1 = second.OP1.pos; const OP2 = second.OP2.pos; const O5 = second.O5.pos; const P = second.P.pos;
-
-        shiftVertex(O3, P, scale);
-        shiftVertex(OP1, P, scale);
-        shiftVertex(OP2, P, scale);
-        shiftVertex(O5, P, scale);
-        calcMidpoint(mp, O3, O5);
-
-        mb.currentGroup = firsLocIndex;
-        let pb = PrimitiveBuilder(3);
-        /* Upper part (for first residue in step) */
-        pb.add(O3, OP1, OP2);
-        pb.add(O3, mp, OP1);
-        pb.add(O3, OP2, mp);
-        MeshBuilder.addPrimitive(mb, t, pb.getPrimitive());
-
-        /* Lower part (for second residue in step */
-        mb.currentGroup = secondLocIndex;
-        pb = PrimitiveBuilder(3);
-        pb.add(mp, O5, OP1);
-        pb.add(mp, OP2, O5);
-        pb.add(O5, OP2, OP1);
-        MeshBuilder.addPrimitive(mb, t, pb.getPrimitive());
-    };
-
-    const walker = new ConfalPyramidsUtil.UnitWalker(structure, unit, handler);
-    walker.walk();
+    const vertexCount = (6 * steps.length) / mapping.length;
+
+    const mb = MeshBuilder.createState(vertexCount, vertexCount / 10, mesh);
+
+    const it = new ConfalPyramidsIterator(structure, unit);
+    while (it.hasNext) {
+        const allPoints = it.move();
+
+        for (const points of allPoints) {
+            const { O3, P, OP1, OP2, O5, confalScore } = points;
+            const scale = (confalScore - 20.0) / 100.0;
+            // Steps can be drawn in a different order than they are stored.
+            // To make sure that we can get from the drawn pyramid back to the step in represents,
+            // we need to use an appropriate groupId. The stepIdx passed from the iterator
+            // is an index into the array of all steps in the structure.
+            // Since a step is drawn as two "half-pyramids" we need two ids to map to a single step.
+            // To do that, we just multiply the index by 2. idx*2 marks the "upper" half-pyramid,
+            // (idx*2)+1 the "lower" half-pyramid.
+            const groupIdx = points.stepIdx * 2;
+
+            unit.conformation.invariantPosition(O3, posO3);
+            unit.conformation.invariantPosition(P, posP);
+            unit.conformation.invariantPosition(OP1, posOP1);
+            unit.conformation.invariantPosition(OP2, posOP2);
+            unit.conformation.invariantPosition(O5, posO5);
+
+            shiftVertex(posO3, posP, scale);
+            shiftVertex(posOP1, posP, scale);
+            shiftVertex(posOP2, posP, scale);
+            shiftVertex(posO5, posP, scale);
+            calcMidpoint(mp, posO3, posO5);
+
+            mb.currentGroup = groupIdx;
+            let pb = PrimitiveBuilder(3);
+            /* Upper part (for first residue in step) */
+            pb.add(posO3, posOP1, posOP2);
+            pb.add(posO3, mp, posOP1);
+            pb.add(posO3, posOP2, mp);
+            MeshBuilder.addPrimitive(mb, t, pb.getPrimitive());
+
+            /* Lower part (for second residue in step) */
+            mb.currentGroup = groupIdx + 1;
+            pb = PrimitiveBuilder(3);
+            pb.add(mp, posO5, posOP1);
+            pb.add(mp, posOP2, posO5);
+            pb.add(posO5, posOP2, posOP1);
+            MeshBuilder.addPrimitive(mb, t, pb.getPrimitive());
+        }
+    }
 
     return MeshBuilder.getMesh(mb);
 }
@@ -124,15 +142,17 @@ function getConfalPyramidLoci(pickingId: PickingId, structureGroup: StructureGro
     const unit = structureGroup.group.units[instanceId];
     if (!Unit.isAtomic(unit)) return EmptyLoci;
 
-    const prop = ConfalPyramidsProvider.get(structure.model).value;
-    if (prop === undefined || prop.data === undefined) return EmptyLoci;
+    const data = ConfalPyramidsProvider.get(structure.model)?.value?.data;
+    if (!data) return EmptyLoci;
+
+    const halfPyramidsCount = data.steps.length * 2;
 
-    const { halfPyramids } = prop.data;
+    if (halfPyramidsCount <= groupId) return EmptyLoci;
 
-    if (halfPyramids.length <= groupId) return EmptyLoci;
-    const hp = halfPyramids[groupId];
+    const idx = Math.floor(groupId / 2); // Map groupIndex to a step, see createConfalPyramidsMesh() for full explanation
+    const step = data.steps[idx];
 
-    return CPT.Loci(hp, [{}]);
+    return CPT.Loci({ step, isLower: groupId % 2 === 1 }, [{}]);
 }
 
 function eachConfalPyramid(loci: Loci, structureGroup: StructureGroup, apply: (interval: Interval) => boolean) {

src/extensions/dnatco/confal-pyramids/types.ts

@@ -30,11 +30,12 @@ export namespace ConfalPyramidsTypes {
         rmsd: number,
     }
 
-    export interface StepsData {
+    export type MappedChains = Map<string, MappedResidues>;
+    export type MappedResidues = Map<number, number[]>;
+
+    export interface Steps {
         steps: Array<Step>,
-        names: Map<string, number>,
-        halfPyramids: Array<HalfPyramid>,
-        hasMultipleModels: boolean
+        mapping: MappedChains[],
     }
 
     export interface HalfPyramid {
@@ -44,8 +45,8 @@ export namespace ConfalPyramidsTypes {
 
     export interface Location extends DataLocation<HalfPyramid, {}> {}
 
-    export function Location(halfPyramid: HalfPyramid) {
-        return DataLocation(DataTag, halfPyramid, {});
+    export function Location(step: Step, isLower: boolean) {
+        return DataLocation(DataTag, { step, isLower }, {});
     }
 
     export function isLocation(x: any): x is Location {

src/extensions/dnatco/confal-pyramids/util.ts

@@ -8,280 +8,120 @@
 import { ConfalPyramidsProvider } from './property';
 import { ConfalPyramidsTypes as CPT } from './types';
 import { Segmentation } from '../../../mol-data/int';
-import { Vec3 } from '../../../mol-math/linear-algebra';
 import { ChainIndex, ElementIndex, ResidueIndex, Structure, StructureElement, StructureProperties, Unit } from '../../../mol-model/structure';
 
-export namespace ConfalPyramidsUtil {
-    type Residue = Segmentation.Segment<ResidueIndex>;
+type Residue = Segmentation.Segment<ResidueIndex>;
 
-    export type AtomInfo = {
-        pos: Vec3,
-        index: ElementIndex,
-        fakeAltId: string,
-    };
+export type Pyramid = {
+    O3: ElementIndex,
+    P: ElementIndex,
+    OP1: ElementIndex,
+    OP2: ElementIndex,
+    O5: ElementIndex,
+    confalScore: number,
+    stepIdx: number,
+};
 
-    export type FirstResidueAtoms = {
-        O3: AtomInfo,
-    };
+const EmptyStepIndices = new Array<number>();
 
-    export type SecondResidueAtoms = {
-        OP1: AtomInfo,
-        OP2: AtomInfo,
-        O5: AtomInfo,
-        P: AtomInfo,
-    };
-
-    type ResidueInfo = {
-        PDB_model_num: number,
-        asym_id: string,
-        auth_asym_id: string,
-        seq_id: number,
-        auth_seq_id: number,
-        comp_id: string,
-        alt_id: string,
-        ins_code: string,
-    };
+function copyResidue(r?: Residue) {
+    return r ? { index: r.index, start: r.start, end: r.end } : void 0;
+}
 
-    export type Handler = (pyramid: CPT.Step, first: FirstResidueAtoms, second: SecondResidueAtoms, firstLocIndex: number, secondLocIndex: number) => void;
+function getAtomIndex(loc: StructureElement.Location, residue: Residue, names: string[], altId: string): ElementIndex {
+    for (let eI = residue.start; eI < residue.end; eI++) {
+        loc.element = loc.unit.elements[eI];
+        const elName = StructureProperties.atom.label_atom_id(loc);
+        const elAltId = StructureProperties.atom.label_alt_id(loc);
 
-    function residueInfoFromLocation(loc: StructureElement.Location): ResidueInfo {
-        return {
-            PDB_model_num: StructureProperties.unit.model_num(loc),
-            asym_id: StructureProperties.chain.label_asym_id(loc),
-            auth_asym_id: StructureProperties.chain.auth_asym_id(loc),
-            seq_id: StructureProperties.residue.label_seq_id(loc),
-            auth_seq_id: StructureProperties.residue.auth_seq_id(loc),
-            comp_id: StructureProperties.atom.label_comp_id(loc),
-            alt_id: StructureProperties.atom.label_alt_id(loc),
-            ins_code: StructureProperties.residue.pdbx_PDB_ins_code(loc)
-        };
+        if (names.includes(elName) && (elAltId === altId || elAltId.length === 0))
+            return loc.element;
     }
 
-    export function hasMultipleModels(unit: Unit.Atomic): boolean {
-        const prop = ConfalPyramidsProvider.get(unit.model).value;
-        if (prop === undefined || prop.data === undefined) throw new Error('No custom properties data');
-        return prop.data.hasMultipleModels;
-    }
+    return -1 as ElementIndex;
+}
 
-    function getPossibleAltIds(residue: Residue, structure: Structure, unit: Unit.Atomic): string[] {
-        const possibleAltIds: string[] = [];
+function getPyramid(loc: StructureElement.Location, one: Residue, two: Residue, altIdOne: string, altIdTwo: string, confalScore: number, stepIdx: number): Pyramid {
+    const O3 = getAtomIndex(loc, one, ['O3\'', 'O3*'], altIdOne);
+    const P = getAtomIndex(loc, two, ['P'], altIdTwo);
+    const OP1 = getAtomIndex(loc, two, ['OP1'], altIdTwo);
+    const OP2 = getAtomIndex(loc, two, ['OP2'], altIdTwo);
+    const O5 = getAtomIndex(loc, two, ['O5\'', 'O5*'], altIdTwo);
 
-        const loc = StructureElement.Location.create(structure, unit, -1 as ElementIndex);
-        for (let rI = residue.start; rI <= residue.end - 1; rI++) {
-            loc.element = unit.elements[rI];
-            const altId = StructureProperties.atom.label_alt_id(loc);
-            if (altId !== '' && !possibleAltIds.includes(altId)) possibleAltIds.push(altId);
-        }
+    return { O3, P, OP1, OP2, O5, confalScore, stepIdx };
+}
 
-        return possibleAltIds;
+export class ConfalPyramidsIterator {
+    private chainIt: Segmentation.SegmentIterator<ChainIndex>;
+    private residueIt: Segmentation.SegmentIterator<ResidueIndex>;
+    private residueOne?: Residue;
+    private residueTwo: Residue;
+    private data?: CPT.Steps;
+    private loc: StructureElement.Location;
+
+    private getStepIndices(r: Residue) {
+        this.loc.element = this.loc.unit.elements[r.start];
+
+        const modelIdx = StructureProperties.unit.model_num(this.loc) - 1;
+        const chainId = StructureProperties.chain.auth_asym_id(this.loc);
+        const seqId = StructureProperties.residue.auth_seq_id(this.loc);
+
+        const chains = this.data!.mapping[modelIdx];
+        if (!chains) return EmptyStepIndices;
+        const residues = chains.get(chainId);
+        if (!residues) return EmptyStepIndices;
+        return residues.get(seqId) ?? EmptyStepIndices;
     }
 
-    class Utility {
-        protected getPyramidByName(name: string): { pyramid: CPT.Step | undefined, index: number } {
-            const index = this.data.names.get(name);
-            if (index === undefined) return { pyramid: undefined, index: -1 };
-
-            return { pyramid: this.data.steps[index], index };
-        }
-
-        protected stepToName(entry_id: string, modelNum: number, locFirst: StructureElement.Location, locSecond: StructureElement.Location, fakeAltId_1: string, fakeAltId_2: string) {
-            const first = residueInfoFromLocation(locFirst);
-            const second = residueInfoFromLocation(locSecond);
-            const model_id = this.hasMultipleModels ? `-m${modelNum}` : '';
-            const alt_id_1 = fakeAltId_1 !== '' ? `.${fakeAltId_1}` : (first.alt_id.length ? `.${first.alt_id}` : '');
-            const alt_id_2 = fakeAltId_2 !== '' ? `.${fakeAltId_2}` : (second.alt_id.length ? `.${second.alt_id}` : '');
-            const ins_code_1 = first.ins_code.length ? `.${first.ins_code}` : '';
-            const ins_code_2 = second.ins_code.length ? `.${second.ins_code}` : '';
-
-            return `${entry_id}${model_id}_${first.auth_asym_id}_${first.comp_id}${alt_id_1}_${first.auth_seq_id}${ins_code_1}_${second.comp_id}${alt_id_2}_${second.auth_seq_id}${ins_code_2}`;
-        }
-
-        constructor(unit: Unit.Atomic) {
-            const prop = ConfalPyramidsProvider.get(unit.model).value;
-            if (prop === undefined || prop.data === undefined) throw new Error('No custom properties data');
-
-            this.data = prop.data;
-            this.hasMultipleModels = hasMultipleModels(unit);
+    private moveStep() {
+        this.residueOne = copyResidue(this.residueTwo);
+        this.residueTwo = copyResidue(this.residueIt.move())!;
 
-            this.entryId = unit.model.entryId.toLowerCase();
-            this.modelNum = unit.model.modelNum;
-        }
-
-        protected readonly data: CPT.StepsData;
-        protected readonly hasMultipleModels: boolean;
-        protected readonly entryId: string;
-        protected readonly modelNum: number;
+        return this.toPyramids(this.residueOne!, this.residueTwo);
     }
 
-    export class UnitWalker extends Utility {
-        private getAtomIndices(names: string[], residue: Residue): ElementIndex[] {
-            const indices: ElementIndex[] = [];
-
-            const loc = StructureElement.Location.create(this.structure, this.unit, -1 as ElementIndex);
-            for (let rI = residue.start; rI <= residue.end - 1; rI++) {
-                loc.element = this.unit.elements[rI];
-                const thisName = StructureProperties.atom.label_atom_id(loc);
-                if (names.includes(thisName)) indices.push(loc.element);
-            }
-
-            if (indices.length === 0) {
-                let namesStr = '';
-                for (const n of names)
-                    namesStr += `${n} `;
+    private toPyramids(one: Residue, two: Residue) {
+        const indices = this.getStepIndices(one);
 
-                throw new Error(`Element [${namesStr}] not found on residue ${residue.index}`);
-            }
-
-            return indices;
+        const points = [];
+        for (const idx of indices) {
+            const step = this.data!.steps[idx];
+            points.push(getPyramid(this.loc, one, two, step.label_alt_id_1, step.label_alt_id_2, step.confal_score, idx));
         }
 
-        private getAtomPositions(indices: ElementIndex[]): Vec3[] {
-            const pos = this.unit.conformation.invariantPosition;
-            const positions: Vec3[] = [];
-
-            for (const eI of indices) {
-                const v = Vec3.zero();
-                pos(eI, v);
-                positions.push(v);
-            }
-
-            return positions;
-        }
-
-        private handleStep(firstAtoms: FirstResidueAtoms[], secondAtoms: SecondResidueAtoms[]) {
-            const modelNum = this.hasMultipleModels ? this.modelNum : -1;
-            let ok = false;
-
-            const firstLoc = StructureElement.Location.create(this.structure, this.unit, -1 as ElementIndex);
-            const secondLoc = StructureElement.Location.create(this.structure, this.unit, -1 as ElementIndex);
-            for (let i = 0; i < firstAtoms.length; i++) {
-                const first = firstAtoms[i];
-                for (let j = 0; j < secondAtoms.length; j++) {
-                    const second = secondAtoms[j];
-                    firstLoc.element = first.O3.index;
-                    secondLoc.element = second.OP1.index;
-
-                    const name = this.stepToName(this.entryId, modelNum, firstLoc, secondLoc, first.O3.fakeAltId, second.OP1.fakeAltId);
-                    const { pyramid, index } = this.getPyramidByName(name);
-                    if (pyramid !== undefined) {
-                        const locIndex = index * 2;
-                        this.handler(pyramid, first, second, locIndex, locIndex + 1);
-                        ok = true;
-                    }
-                }
-            }
-
-            if (!ok) throw new Error('Bogus step');
-        }
-
-        private processFirstResidue(residue: Residue, possibleAltIds: string[]) {
-            const indO3 = this.getAtomIndices(['O3\'', 'O3*'], residue);
-            const posO3 = this.getAtomPositions(indO3);
-
-            const altPos: FirstResidueAtoms[] = [
-                { O3: { pos: posO3[0], index: indO3[0], fakeAltId: '' } }
-            ];
-
-            for (let i = 1; i < indO3.length; i++) {
-                altPos.push({ O3: { pos: posO3[i], index: indO3[i], fakeAltId: '' } });
-            }
-
-            if (altPos.length === 1 && possibleAltIds.length > 1) {
-                /* We have some alternate positions on the residue but O3 does not have any - fake them */
-                altPos[0].O3.fakeAltId = possibleAltIds[0];
-
-                for (let i = 1; i < possibleAltIds.length; i++)
-                    altPos.push({ O3: { pos: posO3[0], index: indO3[0], fakeAltId: possibleAltIds[i] } });
-            }
-
-            return altPos;
-        }
-
-        private processSecondResidue(residue: Residue, possibleAltIds: string[]) {
-            const indOP1 = this.getAtomIndices(['OP1'], residue);
-            const indOP2 = this.getAtomIndices(['OP2'], residue);
-            const indO5 = this.getAtomIndices(['O5\'', 'O5*'], residue);
-            const indP = this.getAtomIndices(['P'], residue);
-
-            const posOP1 = this.getAtomPositions(indOP1);
-            const posOP2 = this.getAtomPositions(indOP2);
-            const posO5 = this.getAtomPositions(indO5);
-            const posP = this.getAtomPositions(indP);
-
-            const infoOP1: AtomInfo[] = [];
-            /* We use OP1 as "pivotal" atom. There is no specific reason
-             * to pick OP1, it is as good a choice as any other atom
-             */
-            if (indOP1.length === 1 && possibleAltIds.length > 1) {
-                /* No altIds on OP1, fake them */
-                for (const altId of possibleAltIds)
-                    infoOP1.push({ pos: posOP1[0], index: indOP1[0], fakeAltId: altId });
-            } else {
-                for (let i = 0; i < indOP1.length; i++)
-                    infoOP1.push({ pos: posOP1[i], index: indOP1[i], fakeAltId: '' });
-            }
-
-            const mkInfo = (i: number, indices: ElementIndex[], positions: Vec3[], altId: string) => {
-                if (i >= indices.length) {
-                    const last = indices.length - 1;
-                    return { pos: positions[last], index: indices[last], fakeAltId: altId };
-                }
-
-                return { pos: positions[i], index: indices[i], fakeAltId: altId };
-            };
-
-            const altPos: SecondResidueAtoms[] = [];
-            for (let i = 0; i < infoOP1.length; i++) {
-                const altId = infoOP1[i].fakeAltId;
-
-                const OP2 = mkInfo(i, indOP2, posOP2, altId);
-                const O5 = mkInfo(i, indO5, posO5, altId);
-                const P = mkInfo(i, indP, posP, altId);
-
-                altPos.push({ OP1: infoOP1[i], OP2, O5, P });
-            }
-
-            return altPos;
-        }
-
-        private step(residue: Residue): { firstAtoms: FirstResidueAtoms[], secondAtoms: SecondResidueAtoms[] } {
-            const firstPossibleAltIds = getPossibleAltIds(residue, this.structure, this.unit);
-            const firstAtoms = this.processFirstResidue(residue, firstPossibleAltIds);
+        return points;
+    }
 
-            residue = this.residueIt.move();
+    constructor(structure: Structure, unit: Unit) {
+        this.chainIt = Segmentation.transientSegments(unit.model.atomicHierarchy.chainAtomSegments, unit.elements);
+        this.residueIt = Segmentation.transientSegments(unit.model.atomicHierarchy.residueAtomSegments, unit.elements);
 
-            const secondPossibleAltIds = getPossibleAltIds(residue, this.structure, this.unit);
-            const secondAtoms = this.processSecondResidue(residue, secondPossibleAltIds);
+        const prop = ConfalPyramidsProvider.get(unit.model).value;
+        this.data = prop?.data;
 
-            return { firstAtoms, secondAtoms };
+        if (this.chainIt.hasNext) {
+            this.residueIt.setSegment(this.chainIt.move());
+            if (this.residueIt.hasNext)
+                this.residueTwo = this.residueIt.move();
         }
 
-        walk() {
-            while (this.chainIt.hasNext) {
-                this.residueIt.setSegment(this.chainIt.move());
-
-                let residue = this.residueIt.move();
-                while (this.residueIt.hasNext) {
-                    try {
-                        const { firstAtoms, secondAtoms } = this.step(residue);
-
-                        this.handleStep(firstAtoms, secondAtoms);
-                    } catch (error) {
-                        /* Skip and move along */
-                        residue = this.residueIt.move();
-                    }
-                }
-            }
-        }
+        this.loc = StructureElement.Location.create(structure, unit, -1 as ElementIndex);
+    }
 
-        constructor(private structure: Structure, private unit: Unit.Atomic, private handler: Handler) {
-            super(unit);
+    get hasNext() {
+        if (!this.data)
+            return false;
+        return this.residueIt.hasNext
+            ? true
+            : this.chainIt.hasNext;
+    }
 
-            this.chainIt = Segmentation.transientSegments(unit.model.atomicHierarchy.chainAtomSegments, unit.elements);
-            this.residueIt = Segmentation.transientSegments(unit.model.atomicHierarchy.residueAtomSegments, unit.elements);
+    move() {
+        if (this.residueIt.hasNext) {
+            return this.moveStep();
+        } else {
+            this.residueIt.setSegment(this.chainIt.move());
+            return this.moveStep();
         }
-
-        private chainIt: Segmentation.SegmentIterator<ChainIndex>;
-        private residueIt: Segmentation.SegmentIterator<ResidueIndex>;
     }
 }