From afe35312e1cb32fbfb7d53e75db8dd71eb3d89ee Mon Sep 17 00:00:00 2001
From: Saveliy Skresanov <savask@yandex.ru>
Date: Sat, 19 Apr 2025 11:13:44 +0700
Subject: [PATCH] Reduce gravity effects on ambient heat.

---
 src/simulation/Air.cpp | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/simulation/Air.cpp b/src/simulation/Air.cpp
index c1be186b4..475e33614 100644
--- a/src/simulation/Air.cpp
+++ b/src/simulation/Air.cpp
@@ -153,18 +153,40 @@ void Air::update_airh(void)
 			// We use the Boussinesq approximation, i.e. we assume density to be nonconstant only
 			// near the gravity term of the fluid equation, and we suppose that it depends linearly on the
 			// difference between the current temperature (hv[y][x]) and some "stationary" temperature (ambientAirTemp).
+			float dvx, dvy;
+			dvx = vx[y][x];
+		       	dvy = vy[y][x];
+
 			if (x>=2 && x<XCELLS-2 && y>=2 && y<YCELLS-2)
 			{
 				float convGravX, convGravY;
 				sim.GetGravityField(x*CELL, y*CELL, -1.0f, -1.0f, convGravX, convGravY);
+
+				// Cap the gravity field
+				float gravMagn = std::sqrt(convGravX*convGravX + convGravY*convGravY);
+				if (gravMagn > 10.0f)
+				{
+					convGravX /= 0.1f*gravMagn;
+					convGravY /= 0.1f*gravMagn;
+				}
+
 				auto weight = (hv[y][x] - ambientAirTemp) / 10000.0f;
 
 				// Our approximation works best when the temperature difference is small, so we cap it from above.
 				if (weight > 0.01f) weight = 0.01f;
 
-				vx[y][x] += weight * convGravX;
-				vy[y][x] += weight * convGravY;
+				dvx += weight * convGravX;
+				dvy += weight * convGravY;
 			}
+
+			// Velocity cap
+			if (dvx > MAX_PRESSURE) dvx = MAX_PRESSURE;
+			if (dvx < MIN_PRESSURE) dvx = MIN_PRESSURE;
+			if (dvy > MAX_PRESSURE) dvy = MAX_PRESSURE;
+			if (dvy < MIN_PRESSURE) dvy = MIN_PRESSURE;
+
+			vx[y][x] = dvx;
+			vy[y][x] = dvy;
 		}
 	}
 	memcpy(hv, ohv, sizeof(hv));