SpringController: name the camera focus point a "focus surface"

Pure rename in preparation for the smooth mesh height tracking rework.

The camera focus height and the zoom-distance-to-focus computation are
about to stop being plain raw-ground lookups, so route them through
GetFocusSurfaceHeight() and DistanceToFocusSurface() wrappers.
Behavior is unchanged: both currently forward to the raw ground.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: PtaQQ

rts/Game/Camera/SpringController.cpp

@@ -253,8 +253,8 @@ float CSpringController::ZoomIn(const float3& curCamPos, const float3& newDir, c
 	const float zoomAmount = std::min(1.0f - scaledMode, (curDistPre - minDist) / curDistPre);
 	const float3 wantedPos = curCamPos + cursorVec * zoomAmount;
 
-	// figure out how far we will end up from the ground at new wanted point
-	curDist = DistanceToGround(wantedPos, dir, pos.y);
+	// figure out how far we will end up from the focus surface at new wanted point
+	curDist = DistanceToFocusSurface(wantedPos);
 	pos = wantedPos + dir * curDist;
 
 	return 0.25f;
@@ -293,7 +293,7 @@ float CSpringController::ZoomOut(const float3& curCamPos, const float3& newDir,
 
 	auto extrapolate_position = [&] (float scale) {
 		const float3 wantedCamPos = curCamPos + cursorVec * (1.0f - scaledMode) * scale;
-		const float newDist = DistanceToGround(wantedCamPos, dir, pos.y);
+		const float newDist = DistanceToFocusSurface(wantedCamPos);
 		return std::pair{wantedCamPos, newDist};
 	};
 
@@ -318,13 +318,26 @@ float CSpringController::ZoomOut(const float3& curCamPos, const float3& newDir,
 
 
 
+float CSpringController::GetFocusSurfaceHeight(float x, float z) const
+{
+	RECOIL_DETAILED_TRACY_ZONE;
+	return CGround::GetHeightReal(x, z, false);
+}
+
+float CSpringController::DistanceToFocusSurface(const float3& from) const
+{
+	RECOIL_DETAILED_TRACY_ZONE;
+	return DistanceToGround(from, dir, pos.y);
+}
+
+
 void CSpringController::Update()
 {
 	RECOIL_DETAILED_TRACY_ZONE;
 
 	pos.x = std::clamp(pos.x, 0.01f, mapDims.mapx * SQUARE_SIZE - 0.01f);
 	pos.z = std::clamp(pos.z, 0.01f, mapDims.mapy * SQUARE_SIZE - 0.01f);
-	pos.y = CGround::GetHeightReal(pos.x, pos.z, false); // always focus on the ground
+	pos.y = GetFocusSurfaceHeight(pos.x, pos.z); // always focus on the ground
 	rot.x = std::clamp(rot.x, math::PI * 0.51f, math::PI * 0.99f);
 
 	// camera->SetRot(float3(rot.x, GetAzimuth(), rot.z));

rts/Game/Camera/SpringController.h

@@ -44,6 +44,8 @@ class CSpringController : public CCameraController
 	inline float ZoomOut(const float3& curCamPos, const float3& dir, const float& curDistPre, const float& scaledMode);
 
 	void SmoothCamHeight(const float3& prevPos);
+	float GetFocusSurfaceHeight(float x, float z) const;
+	float DistanceToFocusSurface(const float3& from) const;
 
 private:
 	float3 rot;