Time08:00

Air-

Ground-

Wind-

Visibility-

1-7 species · click an animal
T take control · WASD move · Shift run
B burrow · H shade · G drink · F fly/land
V camera · Space pause · drag orbit · wheel zoom

Desert World

Loading Blender-built animals and dunes...

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-°C body temperature-

28344046 °C

Water

Fat/food

Microsite temperature: -
Heat from surroundings: -
Metabolic heat: -
Evaporative cooling: -
Water loss now: -
Water lasts about: -

Body temperature and water, last 24 h

Body tempWater %AirGround

Species card

Length
Mass
Diet
Active
Speed

Desert and time

Clock07:00

Peak air44 °C

View

The science

Heat balance. Each animal has one body-temperature node: m c dTb/dt = G (Te - Tb) + Q_met - Q_evap. G = U A (1 + 0.08 wind) is the conductance, A = 0.1 m^2/3 the surface area, Te the effective temperature of where it stands (sun, hot sand, shade, burrow).
Why size matters. A 480 kg camel has a thermal time constant of about 15 hours, so a 40 C+ day barely moves its temperature; a 35 g rat has one of about 13 minutes and overheats within minutes in the open. Small animals must hide, big ones can store heat.
The ground is the real heater. Surface temperature follows the sun: Tg = Tair - 2 + 30 s^1.05 (s = sine of sun elevation), about 20 C at night and 65-70 C at midday. Animals close to it (sidewinder, scorpion, rat) feel far more of it than a tall camel or a flying vulture.
Metabolism. Warm-blooded animals burn 3.4 m^0.75 watts at rest (Kleiber) and shiver (up to 4.5x) if they get too cold. Cold-blooded ones burn about 12 % of that with a Q10 of 2.4, which is why a scorpion can live on a few insects a month.
Cooling costs water. Above its sweating/panting threshold an animal loses k (Tb - Tth) watts to evaporation, and every 2.43 kJ removed costs 1 g of water. A camel raises its threshold from 38.8 to 41 C when it is dehydrated: that heterothermy stores heat instead of spending water.
Microsites. A burrow about a metre deep sits near the daily mean temperature (~28 C) with humid air, so a fennec fox or kangaroo rat both avoids the heat and saves water. Shade removes the solar term and a part of the hot-ground term. The sun and shadow directions are the same as in the 3D scene.
Sandstorm. Wind speed is turned into a friction velocity with the log law, u* = 0.4 U / ln(10 / z0). Sand moves only when u* > 0.22 m/s; the flux is the Bagnold/Lettau form q = 0.22 u*³ (1 - (u*t/u*)²). Sand piling is conserved (dh/dt = -div q), crests move a bit faster than hollows, and slopes steeper than 32 degrees avalanche, which is how the steep slip face forms on the lee side.
What is simplified. One temperature per animal (no gradients), fixed coat/shell properties, no illness or death, no predation. Dunes run on a time-lapse clock (about 60x on top of the simulated clock) because real dunes move metres per year. Small animals are drawn 2-5x life size and walk faster than reality so that a day fits in minutes. Soaring is represented by cooler air (about 5 C) rather than 800 m of real altitude.

How to play

Click an animal (or a species tile, keys 1-7) to select it and watch its body temperature and water.
Drag the clock to noon and watch the ground reach about 70 C: the fox, snake, scorpion and rat should be underground, the camel in shade, the vulture soaring.
Press Take control and steer with WASD or the joystick. Walk to a burrow mound or the oasis and press Burrow or Drink; try standing in the open at noon.
Start sandstorm: visibility drops, animals shelter, and the dunes slowly walk downwind.

All animals, plants, rocks and the dune field were modelled in Blender (Python) and exported as Draco GLB.