Initial commit: bt411 -- standalone Windows BattleTech (Tesla 4.10 port)

Clean, self-contained extraction of the BattleTech-specific work from the
reverse-engineering workspace -- engine + game + content + build, with nothing
from Red Planet or the raw archive dumps. Builds green (Win32) and runs the
single-player drive->animate->target->fire->damage->destroy loop out of the box.

Layout:
  engine/   MUNGA + MUNGA_L4 shared 2007 engine, carrying our BT render/loader
            work (bgfload/L4D3D/L4VIDEO: BSL bit-slice decode, LOD/ground/shadow
            models) + image codec; the minimal rp/ headers the audio HAL needs
  game/     reconstructed BT logic + surviving-original BT source + fwd shims
            + WinMain launcher
  content/  full runtime tree (BTL4.RES, VIDEO/, GAUGE/, AUDIO/, eggs, BTDPL.INI)
  docs/     format specs + reconstruction ledgers
  reference/ raw Ghidra pseudocode (recon source-of-truth) + decomp exporter
  tools/    MP console emulator + map/resource scanners

One top-level CMake builds munga_engine lib + bt410_l4 game lib + btl4.exe.
All paths relativized (186 fwd shims + ~437 CMake abs paths -> repo-relative);
DXSDK is the one external, overridable via -DDXSDK. Verified: builds to a
byte-identical 2.27MB exe and runs combat (TARGET DESTROYED, 0 crashes) against
the bundled content.

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

engine/MUNGA/RAY.cpp

@@ -0,0 +1,168 @@
+#include "munga.h"
+#pragma hdrstop
+
+#include "ray.h"
+#include "plane.h"
+#include "sphere.h"
+
+//
+//#############################################################################
+//#############################################################################
+//
+void Ray::Project(Scalar length, Point3D *result)
+{
+	Check(this);
+	Check(result);
+
+	Vector3D temp;
+
+	temp.Multiply(direction,length);
+	result->Add(origin,temp);
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+Scalar Ray::LengthToClosestPointTo(const Point3D &point)
+{
+	Check(this);
+	Check(&point);
+
+	Vector3D temp;
+
+	temp.Subtract(point,origin);
+	return temp*direction;
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+Scalar Ray::DistanceTo(const Plane &plane, Scalar *product) const
+{
+	Scalar t;
+
+	//
+	//------------------------------------------------------------------
+	// Compute the dot product of the ray and plane normal, and find the
+	// distance from the origin of the ray to the plane
+	//------------------------------------------------------------------
+	//
+	*product = plane.normal * direction;
+	t = plane.DistanceTo(origin);
+
+	//
+	//----------------------------------------------------------------------
+	// If the ray is not parallel to the plane, determine how far to proceed
+	// along the ray until we hit the plane
+	//----------------------------------------------------------------------
+	//
+	if (!Small_Enough(*product))
+		t /= -*product;
+	return t;
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+Scalar Ray::DistanceTo(const Sphere &sphere, Scalar *penetration) const
+{
+	Scalar b, c;
+	Vector3D temp;
+
+	//
+	//-------------------------------------------------------------------------
+	// Set up to solve a quadratic equation for the intersection of the ray and
+	// sphere.  The solution is based on finding the closest point on the line
+	// to the sphere, and then calculating the interval between the entry and
+	// exit points of the ray
+	//-------------------------------------------------------------------------
+	//
+	temp.Subtract(origin,sphere.center);
+	b = 2.0f * (direction * temp);
+	c = temp.LengthSquared() - sphere.radius*sphere.radius;
+
+	//
+	//--------------------------------------------------------------------------
+	// Compute the squared interval to use for the solution.  If it is negative,
+	// then the ray misses the sphere
+	//--------------------------------------------------------------------------
+	//
+	*penetration = b*b - 4.0f*c;
+	if (*penetration<SMALL)
+		return 0.0f;
+	else
+	{
+		//-------------------------------------------------------------------------
+		// Otherwise, find the linear distance along the line of the entry point by
+		// subtracting half the interval between entry and exit points from the
+		// distance to the closest point on the sphere
+		//-------------------------------------------------------------------------
+		*penetration = Sqrt(*penetration);
+		return -0.5f*(b+*penetration);
+	}
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+Logical Ray::TestInstance() const
+{
+	return true;
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+Scalar Find_Closest_Approach(const Point3D& origin1, const Vector3D& velocity1, Point3D *result1, const Point3D& origin2, const Vector3D& velocity2, Point3D *result2, Scalar *time, Logical *constant)
+{
+	Vector3D a,b;
+	a.Subtract(origin1, origin2);
+	b.Subtract(velocity1, velocity2);
+
+	//
+	//--------------------------------------------------------------------
+	// If the velocities are identical, any point will do for the test, so
+	// simply return the difference between the starting points
+	//--------------------------------------------------------------------
+	//
+	Scalar d = b.LengthSquared();
+	if (Small_Enough(d))
+	{
+		*constant = True;
+		d = a.Length();
+		Check_Fpu();
+		return d;
+	}
+
+	//
+	//-------------------------------------------------------------------------
+	// The velocities are not parallel, so figure out when the closest approach
+	// is via the derivative
+	//-------------------------------------------------------------------------
+	//	
+	*constant = False;
+	*time = (a * b) / -d;
+	Check_Fpu();
+
+	//
+	//------------------------------------------------------
+	// Now, plot the resultant points of both line equations
+	//------------------------------------------------------
+	//
+	Vector3D closest;
+	closest.AddScaled(a, b, *time);
+	result1->AddScaled(origin1, velocity1, *time);
+	result2->AddScaled(origin2, velocity2, *time);
+	d = closest.Length();
+	Check_Fpu();
+	return d;
+}
+
+#if defined(TEST_CLASS)
+#	include "ray.tcp"
+#endif