wip, add dashed in lines builder

src/mol-geo/geometry/lines/lines-builder.ts

@@ -1,5 +1,5 @@
 /**
- * Copyright (c) 2018 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ * Copyright (c) 2018-2019 mol* contributors, licensed under MIT, See LICENSE file for more info.
  *
  * @author Alexander Rose <alexander.rose@weirdbyte.de>
  */
@@ -12,12 +12,15 @@ import { Cage } from '../../../mol-geo/primitive/cage';
 
 export interface LinesBuilder {
     add(startX: number, startY: number, startZ: number, endX: number, endY: number, endZ: number, group: number): void
+    addFixedCountDashes(start: Vec3, end: Vec3, segmentCount: number, group: number): void
+    addFixedLengthDashes(start: Vec3, end: Vec3, segmentLength: number, group: number): void
     addCage(t: Mat4, cage: Cage, group: number): void
     getLines(): Lines
 }
 
-const tmpVecA = Vec3.zero()
-const tmpVecB = Vec3.zero()
+const tmpVecA = Vec3()
+const tmpVecB = Vec3()
+const tmpDir = Vec3()
 
 export namespace LinesBuilder {
     export function create(initialCount = 2048, chunkSize = 1024, lines?: Lines): LinesBuilder {
@@ -42,8 +45,29 @@ export namespace LinesBuilder {
             ChunkedArray.add3(indices, offset + 1, offset + 3, offset + 2);
         }
 
+        const addFixedCountDashes = (start: Vec3, end: Vec3, segmentCount: number, group: number) => {
+            const d = Vec3.distance(start, end)
+            const s = Math.floor(segmentCount / 2)
+            const step = 1 / segmentCount
+
+            Vec3.sub(tmpDir, end, start)
+            for (let j = 0; j < s; ++j) {
+                const f = step * (j * 2 + 1)
+                Vec3.setMagnitude(tmpDir, tmpDir, d * f)
+                Vec3.add(tmpVecA, start, tmpDir)
+                Vec3.setMagnitude(tmpDir, tmpDir, d * step * ((j + 1) * 2))
+                Vec3.add(tmpVecB, start, tmpDir)
+                add(tmpVecA[0], tmpVecA[1], tmpVecA[2], tmpVecB[0], tmpVecB[1], tmpVecB[2], group)
+            }
+        }
+
         return {
             add,
+            addFixedCountDashes,
+            addFixedLengthDashes: (start: Vec3, end: Vec3, segmentLength: number, group: number) => {
+                const d = Vec3.distance(start, end)
+                addFixedCountDashes(start, end, d / segmentLength, group)
+            },
             addCage: (t: Mat4, cage: Cage, group: number) => {
                 const { vertices, edges } = cage
                 for (let i = 0, il = edges.length; i < il; i += 2) {