Worldbuilding
Scatter Density Calculator
Direct answer
Scatter density is instances per square metre. Multiply it by your area to get the total count: 0.08 trees per square metre across a 100 by 100 m field is 800 trees. The average gap between them is one divided by the square root of the density, which for 0.08 is about 3.5 m.
See the reference table below for realistic values.
Masks, paths and clearings usually take a large bite out of the nominal area.
Result
- Total instances
- —
- Gross area
- —m2
- Planted area
- —m2
- Average spacing
- —m
- Density per hectare
- —per ha
Method & assumptions
How this is worked out
The count is simply area x density x coverage. What people underestimate is the coverage term: a 100 x 100 m field with a road, a clearing and a lake through it might only be 60 % plantable, and that is the difference between 800 and 480 trees.
Average spacing comes from the density directly: spacing = 1 / sqrt(density). It is the useful sanity check, because a density looks abstract while a spacing does not. If the calculator says your forest averages 40 cm between mature oaks, the density is wrong.
Densities that produce a believable result
| What you are scattering | per m2 | Average spacing |
|---|---|---|
| Grass blades (individual) | 200 – 1000 | 3 – 7 cm |
| Grass and weed clumps | 20 – 60 | 13 – 22 cm |
| Ferns, small bushes | 0.5 – 3 | 0.6 – 1.4 m |
| Undergrowth shrubs | 0.2 – 0.8 | 1.1 – 2.2 m |
| Young or dense plantation trees | 0.1 – 0.3 | 1.8 – 3.2 m |
| Mature forest trees | 0.02 – 0.08 | 3.5 – 7 m |
| Scattered rocks and boulders | 0.05 – 0.3 | 1.8 – 4.5 m |
| Ground debris, twigs, leaves | 1 – 5 | 0.45 – 1 m |
Real mature woodland runs 400 to 800 stems per hectare, which is 0.04 to 0.08 per square metre. Game forests are usually planted denser than reality because the player only ever sees a slice of them.
Questions
How many trees per square metre is realistic?
Mature woodland is far sparser than most people guess: 0.02 to 0.08 trees per square metre, or 200 to 800 per hectare. Denser than about 0.15 and you are building a plantation, which is a legitimate look but a very different one.
Why is my forest too dense even at a low density value?
Usually because the density is applied to the gross area while the canopy is what the player reads. Two trees 3 m apart with 6 m canopies form a solid wall. Check the average spacing against your mesh's actual width, not its trunk.
Does instance count or density drive performance?
Count, but only the visible portion of it. A million instances across a large map costs little if culling and LODs are set up; a hundred thousand all inside the frustum at LOD0 will cost you the frame. The foliage budget calculator covers that side.