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Rubber balls should now target the first kart again; improved handling

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of the situation that the target kart is lost (e.g. it might have finished
the race), so that the ball smoothly aims at the new target now.


git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@9547 178a84e3-b1eb-0310-8ba1-8eac791a3b58
This commit is contained in:
hikerstk 2011-08-17 23:06:48 +00:00
parent 2824225df2
commit a6414b08b4
2 changed files with 117 additions and 144 deletions
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241
src/items/rubber_ball.cpp
View File

@ -43,40 +43,51 @@ RubberBall::RubberBall(Kart *kart)
setAdjustUpVelocity(false);
m_max_lifespan = 9999;
m_target = NULL;
// Just init the previoux coordinates with some value that's not getXYZ()
m_previous_xyz = m_owner->getXYZ();
computeTarget();
// Get 4 points for the interpolation
// Determine distance along track
// Initialises the current graph node
TrackSector::update(getXYZ());
m_control_points[0] = m_owner->getXYZ();
initializeControlPoints(m_owner->getXYZ());
// At the start the ball aims at quads till it gets close enough to the
// target:
m_aiming_at_target = false;
m_timer = 0.0f;
m_interval = m_st_interval;
m_current_max_height = m_max_height;
} // RubberBall
// -----------------------------------------------------------------------------
/** Sets up the control points for the interpolation. The parameter contains
* the coordinates of the first control points (i.e. a control point that
* influences the direction the ball is flying only, not the actual
* coordinates - see details about Catmull-Rom splines). This function will
* then set the 2nd control point to be the current coordinates of the ball,
* and find two more appropriate control points for a smooth movement.
* \param xyz Coordinates of the first control points.
*/
void RubberBall::initializeControlPoints(const Vec3 &xyz)
{
m_control_points[0] = xyz;
m_control_points[1] = getXYZ();
m_last_aimed_graph_node = getSuccessorToHitTarget(getCurrentGraphNode());
// This call defined m_control_points[3], but also sets a new
// m_last_aimed_graph_node, which is further away from the current point,
// which avoids the problem that the ball might go too quickly to the
// left or right when firing the ball off track.
static int xx=0;
xx++; if(xx>1) xx=0;
if(xx) getNextControlPoint();
getNextControlPoint();
m_control_points[2] =
QuadGraph::get()->getQuadOfNode(m_last_aimed_graph_node).getCenter();
// This updates m_last_aimed_graph_node, and sets m_control_points[3]
getNextControlPoint();
m_length_cp_1_2 = (m_control_points[2]-m_control_points[1]).length();
m_t = 0;
m_t_increase = m_speed/m_length_cp_1_2;
// At the start the ball aims at quads till it gets close enough to the
// target:
m_aiming_at_target = false;
m_wrapped_around = false;
m_timer = 0.0f;
m_interval = m_st_interval;
m_current_max_height = m_max_height;
} // RubberBall
} // initialiseControlPoints
// -----------------------------------------------------------------------------
/** Determines the first kart. If a target has already been identified in an
@ -193,47 +204,32 @@ void RubberBall::update(float dt)
hit(NULL);
return;
}
checkDistanceToTarget();
// FIXME: do we want to test if we have overtaken the target kart?
m_previous_xyz = getXYZ();
// If we have reached or overshot the next control point, move to the
// the next section of the spline
m_t += m_t_increase * dt;
if(m_t > 1.0f)
Vec3 next_xyz;
if(m_aiming_at_target)
{
// Move the control points and estimated distance forward.
for(unsigned int i=1; i<4; i++)
m_control_points[i-1] = m_control_points[i];
m_length_cp_1_2 = m_length_cp_2_3;
int old = m_last_aimed_graph_node;
//
// This automatically sets m_control_points[3]
getNextControlPoint();
//printf("1_2 %f length %f\n", m_length_cp_1_2,
// (m_control_points[2]-m_control_points[1]).length());
m_t_increase = m_speed/m_length_cp_1_2;
m_t -= 1.0f;
// If the rubber ball is already close to a target, i.e. aiming
// at it directly, stop interpolating, instead fly straight
// towards it.
Vec3 diff = m_target->getXYZ()-getXYZ();
next_xyz = getXYZ() + (dt*m_speed/diff.length())*diff;
}
else
{
interpolate(&next_xyz, dt);
}
Vec3 next_xyz = 0.5f * ((-m_control_points[0] + 3*m_control_points[1] -3*m_control_points[2] + m_control_points[3])*m_t*m_t*m_t
+ (2*m_control_points[0] -5*m_control_points[1] + 4*m_control_points[2] - m_control_points[3])*m_t*m_t
+ (-m_control_points[0]+m_control_points[2])*m_t
+ 2*m_control_points[1]);
float old_distance = getDistanceFromStart();
// Determine new distance along track
TrackSector::update(next_xyz);
float track_length = World::getWorld()->getTrack()->getTrackLength();
// Detect if the ball crossed the start line
m_wrapped_around = old_distance > 0.9f * track_length &&
getDistanceFromStart()< 10.0f;
m_timer += dt;
float height = updateHeight();
next_xyz.setY(getHoT()+height);
// Determine new distance along track
TrackSector::update(next_xyz);
// Ball squashing:
// ===============
// If we start squashing the ball as soon as the height is smaller than
@ -250,6 +246,38 @@ void RubberBall::update(float dt)
setXYZ(next_xyz);
} // update
// ----------------------------------------------------------------------------
/** Uses Hermite splines (Catmull-Rom) to interpolate the position of the
* ball between the control points. If the next point would be outside of
* the spline between control_points[1] and [2], a new control point is
* added.
* \param next_xyz Returns the new position.
* \param The time step size.
*/
void RubberBall::interpolate(Vec3 *next_xyz, float dt)
{
// If we have reached or overshot the next control point, move to the
// the next section of the spline
m_t += m_t_increase * dt;
if(m_t > 1.0f)
{
// Move the control points and estimated distance forward.
for(unsigned int i=1; i<4; i++)
m_control_points[i-1] = m_control_points[i];
m_length_cp_1_2 = m_length_cp_2_3;
// This automatically sets m_control_points[3]
getNextControlPoint();
m_t_increase = m_speed/m_length_cp_1_2;
m_t -= 1.0f;
}
*next_xyz = 0.5f * ((-m_control_points[0] + 3*m_control_points[1] -3*m_control_points[2] + m_control_points[3])*m_t*m_t*m_t
+ (2*m_control_points[0] -5*m_control_points[1] + 4*m_control_points[2] - m_control_points[3])*m_t*m_t
+ (-m_control_points[0]+m_control_points[2])*m_t
+ 2*m_control_points[1]);
} // interpolate
// ----------------------------------------------------------------------------
/** Updates the height of the rubber ball, and if necessary also adjusts the
* maximum height of the ball depending on distance from the target. The
@ -306,106 +334,49 @@ float RubberBall::updateHeight()
} // updateHeight
// ----------------------------------------------------------------------------
/** Determines which coordinates the ball should aim at next. If the ball is
* still 'far' away from the target (>20), then it will aim at the next
* graph node. If it's closer, the ball will aim directly at the kart and
* keep on aiming at the kart, it will not follow the drivelines anymore.
* \param aim_xyz On return contains the xyz coordinates to aim at.
*/
void RubberBall::determineTargetCoordinates(float dt, Vec3 *aim_xyz)
void RubberBall::checkDistanceToTarget()
{
// If aiming at target phase, keep on aiming at target.
// ----------------------------------------------------
if(m_aiming_at_target)
{
*aim_xyz = m_target->getXYZ();
return;
}
// Aiming at a graph node
// ----------------------
GraphNode *gn = &(QuadGraph::get()->getNode(m_last_aimed_graph_node));
// At this stage getDistanceFromStart() is already the new distance (set
// in the previous time step when aiming). It has to be detected if the
// ball is now ahead of the graph node, and if so, the graph node has to
// be updated till it is again ahead of the ball. Three distinct cases
// have to be considered:
// 1) The ball just crossed the start line (-> distance close to 0),
// but the graph node is still before the start line, in which case
// a new graph node has to be determined.
// 2) The ball hasn't crossed the start line, but the graph node has
// (i.e. graph node is 0), in which case the graph node is correct.
// This happens after the first iteration, i.e. graph node initially
// is the last one (distance close to track length), but if the ball
// is ahead (distance of a graph node is measured to the beginning of
// the quad, so if the ball is in the middle of the last quad it will
// be ahead of the graph node!) the graph node will be set to the
// first graph node (distance close to 0). In this case the graph node
// should not be changed anymore.
// 3) All other cases that do not involve the start line at all
// (including e.g. ball and graph node crossed start line, neither
// ball nor graph node crossed start line), which means that a new
// graph node need to be determined only if the distance along track
// of the ball is greater than the distance for
float gn_distance = gn->getDistanceFromStart();
float track_length = World::getWorld()->getTrack()->getTrackLength();
// Test 1: ball wrapped around, and graph node is close to end of track
bool ball_ahead = m_wrapped_around && gn_distance >0.9f*track_length;
// Test 3: distance of ball greater than distance of graph node
if(!ball_ahead && gn_distance < getDistanceFromStart())
// The distance test only applies if the graph node hasn't wrapped
// around
ball_ahead = true;
while(ball_ahead)
{
// FIXME: aim better if necessary!
m_last_aimed_graph_node = getSuccessorToHitTarget(m_last_aimed_graph_node);
gn = &(QuadGraph::get()->getNode(m_last_aimed_graph_node));
// Detect a wrap around of the graph node. We could just test if
// the index of the new graph node is 0, but since it's possible
// that we might have tracks with a more complicated structure, e.g
// with two different start lines, we use this more general test:
// If the previous distance was close to the end of the track, and
// the new distance is close to 0, the graph node wrapped around.
// This test prevents an infinite loop if the ball is on the last
// quad, in which case no graph node would fulfill the distance test.
if(gn_distance > 0.9f*track_length &&
gn->getDistanceFromStart()<10.0f)
break;
gn_distance = gn->getDistanceFromStart();
ball_ahead = m_wrapped_around && gn_distance >0.9f*track_length;
ball_ahead = !ball_ahead &&
gn->getDistanceFromStart() < getDistanceFromStart();
}
if(m_aiming_at_target) return;
const LinearWorld *world = dynamic_cast<LinearWorld*>(World::getWorld());
if(!world) return; // FIXME battle mode
float target_distance =
world->getDistanceDownTrackForKart(m_target->getWorldKartId());
float ball_distance = getDistanceFromStart();
// Handle wrap around of distance if target crosses finishing line
if(getDistanceFromStart() > target_distance)
target_distance += world->getTrack()->getTrackLength();
// If the ball is close enough, start aiming directly at the target kart
// ---------------------------------------------------------------------
if(target_distance-getDistanceFromStart()< 20)
float diff = target_distance - ball_distance;
if(diff < 0)
{
m_aiming_at_target = true;
*aim_xyz = m_target->getXYZ();
return;
diff += world->getTrack()->getTrackLength();
}
// ------------------------------
*aim_xyz = gn->getQuad().getCenter();
if(diff < 50)
{
m_aiming_at_target = true;
return;
}
else if(m_aiming_at_target)
{
// It appears that we have lost the target. It was within
// the target distance, and now it isn't. That means either
// the original target escaped, or perhaps that there is a
// new target. In this case we have to reset the control
// points, since it's likely that the ball is (after some time
// going directly towards the target) far outside of the
// old control points.
} // determineTargetCoordinates
// We use the previous XYZ point to define the first control
// point, which results in a smooth transition from aiming
// directly at the target back to interpolating again.
initializeControlPoints(m_previous_xyz);
m_aiming_at_target = false;
}
return;
} // checkDistanceToTarget
// ----------------------------------------------------------------------------
/** Callback from the physics in case that a kart or object is hit. The rubber

14
src/items/rubber_ball.hpp
View File

@ -52,6 +52,11 @@ private:
* for interpolation. */
Vec3 m_control_points[4];
/** Saves the previous location of the ball. This is needed if a ball
* should lose it target, and has to reinitialise the control points
* for the interpolation. */
Vec3 m_previous_xyz;
/** Estimated length of the spline between the control points
* 1 and 2. */
float m_length_cp_1_2;
@ -86,11 +91,6 @@ private:
* reduced if the ball gets closer to the target. */
float m_current_max_height;
/** True if the ball just crossed the start line, i.e. its
* distance changed from close to length of track in the
* previous time step to a bit over zero now. */
bool m_wrapped_around;
/** Once the ball is close enough, it will aim for the kart. If the
* kart should be able to then increase the distance to the ball,
* the ball will be removed and the kart escapes. This boolean is
@ -98,11 +98,13 @@ private:
bool m_aiming_at_target;
void computeTarget();
void determineTargetCoordinates(float dt, Vec3 *aim_xyz);
void checkDistanceToTarget();
unsigned int getSuccessorToHitTarget(unsigned int node_index,
float *f=NULL);
void getNextControlPoint();
float updateHeight();
void interpolate(Vec3 *next_xyz, float dt);
void initializeControlPoints(const Vec3 &xyz);
public:
RubberBall (Kart* kart);
static void init(const XMLNode &node, scene::IMesh *bowling);