Texture resolution formula

The Demetrescu-d’Annibale texture resolution formula is the algorithm 3DSC uses to compute how many texture pages are needed to texture a segmented photogrammetric tile at a target ground resolution. It is the single source of truth for every place in the documentation that quotes the formula — the Metashape tool reference and the Digital Replica Phase 3 how-to both link back here.

The formula was published in Demetrescu et Alii 2026 and is implemented in the 3DSC for Metashape script package.

The formula

For a given tile area and target texel size, the number of texture pages needed to cover the tile is:

\[N_{\text{tex}} = \frac{(10000 / r_{\text{texel}})^2}{t_{\text{res}}^2 \times ratio}\]

Where:

  • \(r_{\text{texel}}\) = target resolution in mm/texel (typically 1.2 mm for archaeological VR; default in the script is 1.26 mm)

  • \(t_{\text{res}}\) = texture page resolution in pixels (typically 4096)

  • \(ratio\) = surface coverage efficiency factor (typically 0.6) — accounts for UV-space packing inefficiency

The result \(N_{\text{tex}}\) is the number of 4096×4096 texture pages per 100 m² of tile surface; scale by tile area to obtain the actual count.

Worked example

For a 100 m² tile at 1.2 mm/texel with 4096 px texture pages and ratio 0.6:

\[N_{\text{tex}} = \frac{(10000 / 1.2)^2}{4096^2 \times 0.6} \approx 6\]

Result: 6 textures at 4096×4096 px per 100 m² tile.

Reference table

Indicative texture counts at 1.26 mm/texel, 4096 px pages, ratio 0.6:

Area (m²)

Textures (4096px)

Total Pixels

Est. File Size

Resolution

10

1

16.7 MP

15 MB

1.26 mm/px

50

3

50.3 MP

45 MB

1.26 mm/px

100

6

100.6 MP

90 MB

1.26 mm/px

200

12 (capped)

201.3 MP

180 MB

1.26 mm/px

Reference implementation

The formula is implemented in texturize_it.py (and in the 3DSC_MS_GUI.py single-file build) as:

numtex = pow((10000 / x_res_a_terra), 2) / (tex * tex * ratio)
numtex_x_area = (numtex * area_model) / 100
tex_num = max(1, round(numtex_x_area, 0))

Where the variables map to the formula as:

  • x_res_a_terra → \(r_{\text{texel}}\)

  • tex → \(t_{\text{res}}\)

  • ratio → \(ratio\)

  • area_model → tile area in m² (computed from the imported mesh)

Why these defaults

The 1.2–1.26 mm/texel target was chosen as the sweet spot for archaeological and architectural heritage documentation:

  • Sufficient detail to identify tool marks, inscriptions, and small surface features at one-to-one viewing distance.

  • VR-ready — balances visual quality with the texture-memory budget of consumer headsets.

  • Real-time engine compatible — texture page sizes (4096 px) match the upload constraints of Unreal, Unity, Godot and O3DE.

  • Storage-aware — the table above shows the formula avoids producing excessive PNG files even for 200 m² tiles.

The 0.6 ratio factor empirically accounts for the unavoidable UV-space waste introduced by atlasing curved or vertical surfaces.

See also