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bugfix(physics): Fix diagonal movement speed discrepancy #3003

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bugfix(physics): Fix diagonal movement speed discrepancy #3003

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7be8457
bugfix(physics): Fix diagonal movement speed discrepancy
xezon Jul 22, 2026
6f4def0
Preserve legacy speeds for scripted movements
xezon Jul 29, 2026
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11 changes: 11 additions & 0 deletions Core/GameEngine/Include/Common/GameDefines.h
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,17 @@
#define PRESERVE_RETAIL_SCRIPTED_CAMERA (1) // Retain scripted camera behavior present in retail Generals 1.08 and Zero Hour 1.04
#endif

// Whether to preserve the 1.41x speed discrepancy between straight and diagonal movements of all objects.
#ifndef PRESERVE_RETAIL_PHYSICS_FORWARD_SPEED
#define PRESERVE_RETAIL_PHYSICS_FORWARD_SPEED (1)
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#endif

// Whether to preserve the 1.41x speed discrepancy between straight and diagonal movements of all scripted objects.
// This setting is very relevant for legacy missions and cinematic sequences.
#ifndef PRESERVE_RETAIL_SCRIPTED_PHYSICS_FORWARD_SPEED
#define PRESERVE_RETAIL_SCRIPTED_PHYSICS_FORWARD_SPEED (1)
#endif

#ifndef RETAIL_COMPATIBLE_CRC
#define RETAIL_COMPATIBLE_CRC (1) // Game is expected to be CRC compatible with retail Generals 1.08, Zero Hour 1.04
#endif
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61 changes: 50 additions & 11 deletions GeneralsMD/Code/GameEngine/Source/GameLogic/Object/Update/PhysicsUpdate.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -957,21 +957,39 @@ Real PhysicsBehavior::getVelocityMagnitude() const
Real PhysicsBehavior::getForwardSpeed2D() const
{
const Coord3D *dir = getObject()->getUnitDirectionVector2D();

Real vx = m_vel.x * dir->x;
Real vy = m_vel.y * dir->y;

Real dot = vx + vy;

Real speedSquared = vx*vx + vy*vy;
// DEBUG_ASSERTCRASH( speedSquared != 0, ("zero speedSquared will overflow sqrtf()!") );// lorenzen... sanity check

Real speed = (Real)sqrtf( speedSquared );
#if RETAIL_COMPATIBLE_CRC || PRESERVE_RETAIL_PHYSICS_FORWARD_SPEED

Real speed = (Real)sqrtf( vx*vx + vy*vy );
if (dot >= 0.0f)
return speed;

return -speed;

#else

#if PRESERVE_RETAIL_SCRIPTED_PHYSICS_FORWARD_SPEED
if (const AIUpdateInterface *ai = getObject()->getAIUpdateInterface())
{
if (ai->getLastCommandSource() == CMD_FROM_SCRIPT)
{
Real speed = (Real)sqrtf( vx*vx + vy*vy );
if (dot >= 0.0f)
return speed;
return -speed;
}
}
#endif

// Inverse scale len by (1 + sqrt(2)) / 2 to adjust to the average of the former min/max movement speed.
// The inverse looks intuitively wrong, but it is correct, because the value returned by this function is
// used to determine the additional velocity needed to reach the target speed.
constexpr const Real DiagonalCompensation = 1.0f / 1.20710678f;
return dot * DiagonalCompensation;

#endif
}

//-------------------------------------------------------------------------------------------------
Expand All @@ -982,19 +1000,40 @@ Real PhysicsBehavior::getForwardSpeed2D() const
Real PhysicsBehavior::getForwardSpeed3D() const
{
Vector3 dir = getObject()->getTransformMatrix()->Get_X_Vector();

Real vx = m_vel.x * dir.X;
Real vy = m_vel.y * dir.Y;
Real vz = m_vel.z * dir.Z;

Real dot = vx + vy + vz;

Real speed = (Real)sqrtf( vx*vx + vy*vy + vz*vz );
#if RETAIL_COMPATIBLE_CRC || PRESERVE_RETAIL_PHYSICS_FORWARD_SPEED

Real speed = (Real)sqrtf( vx*vx + vy*vy + vz*vz );
if (dot >= 0.0f)
return speed;

return -speed;

#else

#if PRESERVE_RETAIL_SCRIPTED_PHYSICS_FORWARD_SPEED
if (const AIUpdateInterface *ai = getObject()->getAIUpdateInterface())
{
if (ai->getLastCommandSource() == CMD_FROM_SCRIPT)
{
Real speed = (Real)sqrtf( vx*vx + vy*vy + vz*vz );
if (dot >= 0.0f)
return speed;
return -speed;
}
}
#endif

// Inverse scale len by (1 + sqrt(3)) / 2 to adjust to the average of the former min/max movement speed.
// The inverse looks intuitively wrong, but it is correct, because the value returned by this function is
// used to determine the additional velocity needed to reach the target speed.
constexpr const Real DiagonalCompensation = 1.0f / 1.36602540f;
return dot * DiagonalCompensation;

#endif
}

//-------------------------------------------------------------------------------------------------
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