Should not GuiTraceRay for quads beyond the floor until the far plane.

rts/Game/TraceRay.cpp

@@ -18,6 +18,7 @@
 #include "Sim/Units/UnitTypes/Factory.h"
 #include "Sim/Weapons/PlasmaRepulser.h"
 #include "Sim/Weapons/WeaponDef.h"
+#include "System/GlobalConfig.h"
 #include "System/SpringMath.h"
 
 #include <algorithm>
@@ -403,10 +404,24 @@ float GuiTraceRay(
 	if (groundOnly)
 		return minRayLength;
 
+	// set maximum ray until ground intersection taking lenience into account later
+	float maxRayLength;
+	if (minRayLength >= 0.0) {
+		// normal intersection
+		maxRayLength = minRayLength;
+	} else if (waterRayLength >= 0.0) {
+		// out of map we still want to intersect somewhere if possible
+		maxRayLength = waterRayLength;
+	} else {
+		// pointing upwards
+		maxRayLength = length;
+	}
+	maxRayLength = std::min(maxRayLength + globalConfig.selectThroughGround, length);
+
 	CollisionQuery cq;
 
 	QuadFieldQuery qfQuery;
-	quadField.GetQuadsOnRay(qfQuery, start, dir, length);
+	quadField.GetQuadsOnRay(qfQuery, start, dir, maxRayLength);
 
 	for (const int quadIdx: *qfQuery.quads) {
 		const CQuadField::Quad& quad = quadField.GetQuad(quadIdx);
@@ -493,7 +508,7 @@ float GuiTraceRay(
 		}
 	}
 
-	if ((minRayLength > 0.0f) && ((minRayLength + 200.0f) < minIngressDist)) {
+	if ((minRayLength > 0.0f) && (maxRayLength < minIngressDist)) {
 		minIngressDist = minRayLength;
 
 		hitUnit    = nullptr;

rts/System/GlobalConfig.cpp

@@ -65,6 +65,8 @@ CONFIG(bool, DumpGameStateOnDesync).defaultValue(true).description("Enable writi
 CONFIG(float, MinSimDrawBalance).defaultValue(0.15f).description("Percent of the time for simulation is minimum spend for drawing. E.g. if set to 0.15 then 15% of the total cpu time is exclusively reserved for drawing.");
 CONFIG(int, MinDrawFPS).defaultValue(2).description("Defines how many frames per second should minimally be rendered. To reach this number we will delay simframes.");
 
+CONFIG(float, SelectThroughGround).defaultValue(200.0f).minimumValue(0.0f).description("How far beyond the ground to allow selecting objects.");
+
 void GlobalConfig::Init()
 {
 	// Recommended semantics for "expert" type config values:
@@ -98,6 +100,8 @@ void GlobalConfig::Init()
 	minDrawFPS = configHandler->GetInt("MinDrawFPS");
 
 	teamHighlight = configHandler->GetInt("TeamHighlight");
+
+	selectThroughGround = configHandler->GetFloat("SelectThroughGround");
 }
 #endif
 

rts/System/GlobalConfig.h

@@ -141,6 +141,13 @@ class GlobalConfig {
 	 * rendered. To reach this number we will delay simframes.
 	 */
 	int minDrawFPS;
+
+	/**
+	 * @brief selection ground penetration
+	 *
+	 * Defines how far beyond the ground to allow selecting objects.
+	 */
+	float selectThroughGround;
 };
 
 extern GlobalConfig globalConfig;