Mechanics.cpp

//AlSch092 @ github
#include "Mechanics.hpp"

bool Mechanics::IsColliding(Point3 StartPosition, Vector3 ShootDirection, Point3 TargetPosition, Vector3 TargetWidthHeightDepth) 
{
	// Check if the shot starts inside the target
	if (StartPosition.X >= TargetPosition.X - TargetWidthHeightDepth.X / 2.0f && StartPosition.X <= TargetPosition.X + TargetWidthHeightDepth.X / 2.0f
		&& StartPosition.Y >= TargetPosition.Y - TargetWidthHeightDepth.Y / 2.0f && StartPosition.Y <= TargetPosition.Y + TargetWidthHeightDepth.Y / 2.0f
		&& StartPosition.Z >= TargetPosition.Z - TargetWidthHeightDepth.Z / 2.0f && StartPosition.Z <= TargetPosition.Z + TargetWidthHeightDepth.Z / 2.0f)
		return true;

	//check if shot intersects any of the target's faces
	double tmin = -INFINITY, tmax = INFINITY;

	if (ShootDirection.X != 0.0f)
	{
		double tx1 = (TargetPosition.X - TargetWidthHeightDepth.X / 2.0f - StartPosition.X) / ShootDirection.X;
		double tx2 = (TargetPosition.X + TargetWidthHeightDepth.X / 2.0f - StartPosition.X) / ShootDirection.X;
		tmin = std::max(tmin, std::min(tx1, tx2));
		tmax = std::min(tmax, std::max(tx1, tx2));
	}
	if (ShootDirection.Y != 0.0f)
	{
		double ty1 = (TargetPosition.Y - TargetWidthHeightDepth.Y / 2.0f - StartPosition.Y) / ShootDirection.Y;
		double ty2 = (TargetPosition.Y + TargetWidthHeightDepth.Y / 2.0f - StartPosition.Y) / ShootDirection.Y;
		tmin = std::max(tmin, std::min(ty1, ty2));
		tmax = std::min(tmax, std::max(ty1, ty2));
	}
	if (ShootDirection.Z != 0.0f)
	{
		double tz1 = (TargetPosition.Z - TargetWidthHeightDepth.Z / 2.0f - StartPosition.Z) / ShootDirection.Z;
		double tz2 = (TargetPosition.Z + TargetWidthHeightDepth.Z / 2.0f - StartPosition.Z) / ShootDirection.Z;
		tmin = std::max(tmin, std::min(tz1, tz2));
		tmax = std::min(tmax, std::max(tz1, tz2));
	}

	if (tmax < std::max((double)0.0f, tmin))
		return false;

	return true;
}

std::list<UID> Mechanics::GetEntityInShotLine(list<Entity*> PlayerList, Entity* shooter, Shot* shot)
{
	std::list<UID> actorsHit;

	for each (Entity* e in PlayerList)
	{
		if (Mechanics::IsColliding(shot->StartPosition, shot->Direction, e->StandingPosition, e->Size) && shooter != e)
		{
			printf("Player %d's shot hit Entity %d!\n", shooter->UniqueId, e->UniqueId);
			actorsHit.push_back(e->UniqueId);
		}
	}

	return actorsHit;
}

double Mechanics::GetCorrectiveAngle(Shot* s, Entity* e)
{
	Vector3 toTarget = { e->StandingPosition.X - s->StartPosition.X, e->StandingPosition.Y - s->StartPosition.Y, e->StandingPosition.Z - s->StartPosition.Z };

	//magnitude of the vector from start position to target position
	double toTargetMag = sqrt(pow(toTarget.X, 2) + pow(toTarget.Y, 2) + pow(toTarget.Z, 2));

	//Normalize the direction vector
	double dirMag = sqrt(pow(s->Direction.X, 2) + pow(s->Direction.Y, 2) + pow(s->Direction.Z, 2));

	Vector3 normDir = { s->Direction.X / dirMag, s->Direction.Y / dirMag, s->Direction.Z / dirMag };

	//dot product of the direction vector and the vector from start position to target position
	double dotProd = normDir.X * toTarget.X + normDir.Y * toTarget.Y + normDir.Z * toTarget.Z;

	//angle between the direction vector and the vector from start position to target position
	double angle = acos(dotProd / toTargetMag);

	//radians to degrees
	angle = angle * 180 / M_PI;

	return angle;
}

Vector3 Mechanics::GetCorrectiveVector(Shot* s, Entity* e, float speed)
{
	Vector3 toTarget = { e->StandingPosition.X - s->StartPosition.X, e->StandingPosition.Y - s->StartPosition.Y, e->StandingPosition.Z - s->StartPosition.Z };

	//magnitude of the vector from start position to target position
	double toTargetMag = sqrt(pow(toTarget.X, 2) + pow(toTarget.Y, 2) + pow(toTarget.Z, 2));

	//Normalize the direction vector
	double dirMag = sqrt(pow(s->Direction.X, 2) + pow(s->Direction.Y, 2) + pow(s->Direction.Z, 2));

	Vector3 normDir = { s->Direction.X / dirMag, s->Direction.Y / dirMag, s->Direction.Z / dirMag };

	//dot product of the direction vector and the vector from start position to target position
	double dotProd = normDir.X * toTarget.X + normDir.Y * toTarget.Y + normDir.Z * toTarget.Z;
	printf("dotProd: %f\n", dotProd);

	//angle between the direction vector and the vector from start position to target position
	double angle = acos(dotProd / toTargetMag);
	printf("angle: %f\n", angle);

	//time required for the projectile to reach the target
	double time = toTargetMag / (speed * sin(angle));
	printf("time: %f\n", time);

	//required velocity vector
	Vector3 VelocityVec = { (toTarget.X / time - 0.5 * 0 * time) / cos(angle),
		(toTarget.Y / time - 0.5 * 9.8 * time) / cos(angle),
		(toTarget.Z / time - 0.5 * 0 * time) / cos(angle) };

	return VelocityVec;
}