Calculate interpolated fragment coordinates
All coordinate units must use one consistent local construction reference system.
Example data table
This sample uses local site coordinates with the XY projection plane.
| Input | Example value | Purpose |
|---|---|---|
| Start vertex | (0, 0, 0) | First endpoint of the modeled fragment. |
| End vertex | (120, 45, 12) | Second endpoint in the same local reference frame. |
| Fragment distance | 36 | Distance measured from the start vertex. |
| Fragment length | 130 | Length used to normalize progress. |
| Projection and scale | XY, 0.01 / 0.01 | Converts projected coordinates into material UV values. |
Linear interpolation and UV mapping
First, normalize the fragment distance. Use t = distance / length. Clamp t between zero and one when values must stay on the segment.
P(t) = P0 + t × (P1 − P0)The coordinate P contains X, Y, and Z values. The selected plane provides raw U and V values. Apply material mapping with U = Uraw × scaleU + offsetU and V = Vraw × scaleV + offsetV.
This calculator uses direct linear interpolation. Curved paths need a different path parameterization.
Enter coordinates in a consistent reference system
- Enter the start and end vertex coordinates.
- Enter the current distance and total fragment length.
- Select the plane that best matches your material direction.
- Set scale and offset values for texture repetition or alignment.
- Keep clamping enabled for normal segment interpolation.
- Calculate, then export the verified values as CSV or PDF.
Fragment coordinates for material alignment
Construction visualization often combines measured geometry with repeated material patterns. A surface, wall, utility corridor, or structural member may need a stable material direction. Fragment coordinates help retain that direction while a rendered point moves between two vertices.
Start with a local coordinate system. Use the same origin and units for both vertices. Mixing meters with millimeters gives incorrect positions. The direction vector then describes the change from the first vertex to the second. It is calculated by subtracting the start coordinate from the end coordinate.
The normalized progress value controls interpolation. A value of zero returns the start vertex. A value of one returns the end vertex. A value of one half returns the midpoint. Values between these limits return locations along the straight fragment. Clamping protects the result when a measured distance slightly exceeds the intended length.
Some workflows need extrapolation. For example, a planned extension may continue beyond an existing modeled panel. Disable clamping only when that behavior is deliberate. A negative progress value extends before the start. A progress value above one extends past the end.
Projected UV values are separate from the three-dimensional coordinate. Choose XY for flat plan surfaces. Choose XZ for faces that rise vertically along Z. Choose YZ when the face aligns with Y and Z. The scale values control repetition. Smaller scales create larger material features. Larger scales create denser repetition.
Offsets provide final alignment. They can place a joint, tile edge, pattern seam, or stripe at a specified reference point. Record the selected plane, scale, and offsets with the geometry. This reduces mismatches between modeling, quantity review, and construction presentations.
Use the result as a verification aid, not as a replacement for geometry validation. Check the displayed direction, segment magnitude, and UV result. Confirm that the local axis orientation matches the project model. Verify units before sharing exports with designers or field teams.
Coordinate precision matters near joins and transitions. Round only after final review. Early rounding can move a seam, distort a repeat, or hide a unit mismatch. Store precision in project records. Present rounded values only when drawings, schedules, or visual review standards require them. Document changes.
Reliable coordinate mapping produces clearer materials and easier model reviews. It also supports repeatable checks when construction details change during coordination.
Frequently asked questions
1. What does the progress value t represent?
It is the normalized position along the fragment. Zero is the start vertex. One is the end vertex. A value between them identifies a straight-line location between both vertices.
2. Why is fragment length entered separately?
It converts your measured distance into normalized progress. It can match a stationing length or a controlled shader distance. Use a positive value in the same unit as fragment distance.
3. Does the tool calculate a curved path position?
No. It calculates a linear position between two vertices. Curved alignments need sampled path geometry, arc-length parameterization, or a dedicated spline method.
4. When should I keep progress clamping enabled?
Keep it enabled for ordinary segment work. It prevents calculated coordinates from extending outside the start and end vertices because of input error or small survey rounding differences.
5. What happens when clamping is disabled?
The calculator permits extrapolation. Negative progress extends before the start vertex. Progress above one extends past the end vertex. Use this only for intentional design extensions.
6. Which projection plane should I choose?
Choose XY for horizontal surfaces, XZ for surfaces following X and elevation, and YZ for surfaces following Y and elevation. The best choice follows your material orientation.
7. How do material scales affect UV output?
Each scale multiplies the projected coordinate. A scale of 0.01 converts 100 coordinate units into one UV unit. Adjust scales to control pattern frequency.
8. What are material offsets used for?
Offsets shift the final U or V coordinate. They help align visual seams, tile starts, stripes, or repeated details without changing the underlying vertex coordinates.
9. Can I use world coordinates from a large geospatial model?
You can, but local coordinates are usually easier to inspect. Very large values may reduce clarity during manual review. Keep all inputs in one consistent reference frame.
10. What does segment magnitude show?
It is the straight three-dimensional distance between the two supplied vertices. Compare it with fragment length when both values are intended to describe the same straight segment.
11. Should exported coordinates be checked before model updates?
Yes. Check coordinates carefully before publishing construction visualization results today.