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//============================================================================= // ObjectPath. //============================================================================= class ObjectPath expands Keypoint; // Allows an object to follow a defined path, by specifying // PathPoint nodes. M // Note: At least 4 PathPoints must exist. The first and last // do not need speed/deltaU settings. // Note: If there are N points to interpolate through, there must // be in total N+2 points specified. Point 0 and Point N+1 // are dummy control points, where Point 1-Point 0 is the // initial direction of motion, and Point N+1 - Point N is // the final direction of motion. The object will start at // point 1 and end up at point N. // Uses the Bernstein basis functions for Bezier interpolation: // B0(u) = (1-u)^3 // B1(u) = 3u(1-u)^2 // B2(u) = 3u^2(1-u) // B3(u) = u^3 var() name PathActorTag; // The Tag of the actor which should be moved var() bool bAlterPitch; // should the pitch of the actor be modified during movement var() bool bAlterYaw; // should the yaw ... var() bool bAlterRoll; // should the roll ... var() rotator RAdjust; // Adjust the rotation of the object //var() bool bLoopMotion; // The last PathPoint should lead to the first var Actor PathActor; // what should be moved var PathPoint Path[35]; // maximum 35 nodes in the path, hence 33 real positions var int numPathNodes; // how many elements in the path array var int curNode; // Which node are we at? var float uValue; // Offset in the segment var bool bTriggeredOnce; // Don't repeat the path if it's already played through var bool bPlayedOnce; // Really don't play it again since it's already finished last time var vector lastPosition; // Where the actor was in the most recent frame var rotator lastRotation; // The orientation of the actor in the most recent frame function BeginPlay() { local int i, l; local PathPoint tempPP; // Find all relevant PathPoint elements and load them // into the temporary array (in sorted order). Also set up // velocities, etc.. // Wait until something triggers the motion Disable('Tick'); bTriggeredOnce = false; bPlayedOnce = true; // Find the object which must be moved PathActor = None; foreach AllActors (class 'Actor', PathActor) { if( PathActor.Tag == PathActorTag ) // found the matching Actor break; } if( PathActor == None ) { log("ObjectPath: No object to be moved. Aborting."); Destroy(); return; } // Find all the Path Nodes. numPathNodes=0; foreach AllActors (class 'PathPoint', tempPP) { // This PathPoint must have the same tag as this ObjectPath actor if (tempPP.Tag == Tag) { Path[numPathNodes] = tempPP; numPathNodes++; // Make sure that the user didn't specify too many points if (numPathNodes > 35) { log ("ObjectPath: Maximum number of path elements exceeded. Aborting."); log (" Tag = " $ tempPP.Tag); Destroy(); return; } } } // Make sure that there are at least four PathPoint nodes. if (numPathNodes < 4) { log("ObjectPath: Not enough PathPoints specified. Needed 4. Aborting."); Destroy(); return; } // Now sort the elements (using a crappy bubble sort.. hey it's < 30 elements) for (i=0; i<numPathNodes-1; i++) { for (l=i+1; l<numPathNodes; l++) { if (Path[i].sequence_Number > Path[l].sequence_Number) { // switch them tempPP = Path[i]; Path[i] = Path[l]; Path[l] = tempPP; } } } // Precalculate the direction vectors at each point, based on // relative position and curveSpeed. // The first (1) and last (N-1) segments' velocities are // related to the (0) and (N)'th points respectively. // first segment Path[1].pVelocity = Normal(Path[1].Location - Path[0].Location) * Path[1].curvespeed; // last segment Path[numPathNodes-2].pVelocity = Normal(Path[numPathNodes-1].Location - Path[numPathNodes-2].Location) * Path[numPathNodes-2].curvespeed; // The tangent of the middle nodes is parallel to the vector // between the previous and next nodes. for (i=2; i<=numPathNodes-3; i++) { Path[i].pVelocity = Normal(Path[i+1].Location - Path[i-1].Location) * Path[i].curvespeed; } Enable('Trigger'); } function PostBeginPlay() { Super.PostBeginPlay(); // Set the object at the initial position and orientation, so that it doesn't // suddenly jerk when triggered to move. PathActor.SetLocation( Path[1].Location ); } function Trigger( actor Other, pawn EventInstigator ) { // Play the motion if it hasn't occured yet if( !bTriggeredOnce ) { // Set update parameters bTriggeredOnce = true; bPlayedOnce = false; curNode = 1; uValue = 0; // Put the actor at the initial position PathActor.SetLocation( Path[1].Location ); //PathActor.SetRotation( RAdjust ); //PathActor.SetPhysics( PHYS_None ); // So that the orientation of the object can be set immediately lastPosition = Path[0].Location; lastRotation = PathActor.Rotation; // Start the motion Enable('Tick'); } } function Tick( float DeltaTime ) { local float curSpeedU; local vector actorPosition; local rotator actorRotation; if( bPlayedOnce ) { Disable('Tick'); return; } // Update the position of the object, based on DeltaTime and it's // index in the sequence of positions. // Interpolate the deltaU value from this to the next position, // based on the current U value in the segment. // FIXME: This is not exact by far, and would cause discontinuities // in velocity if the arclengths of the bezier's are different. curSpeedU = (Path[curNode+1].speedU - Path[curNode].speedU)*uValue + Path[curNode].speedU; uValue += curSpeedU * DeltaTime; // Check if the difference sends the point to the next segment (or the one after that, etc..) while( uValue >= 1 && curNode < numPathNodes-2 ) { curNode++; uValue -= 1; } // Check if the point is beyond, or at the end of the path if( curNode >= numPathNodes-2 ) { // Set the position of the object to the position of the last node. PathActor.SetLocation( Path[numPathNodes-2].Location ); PathActor.GotoState(''); // Don't ever play it again!!! bPlayedOnce = true; // Finished the path, discontinue the updates Disable( 'Tick' ); Disable( 'Trigger' ); return; } // Calculate the position of the object based on the current node index // and U offset in the curve segment. // B0(u) = (1-u)^3 Bernstein basis polys // B1(u) = 3u(1-u)^2 // B2(u) = 3u^2(1-u) // B3(u) = u^3 actorPosition = Path[curNode].Location * ((1 - uValue)**3) + (Path[curNode].Location + Path[curNode].pVelocity) * (3*uValue* ((1-uValue)**2)) + (Path[curNode+1].Location - Path[curNode+1].pVelocity) * (3*(uValue**2)* (1-uValue)) + Path[curNode+1].Location * (uValue**3); PathActor.Move( actorPosition - PathActor.Location ); // Calculate new Pitch, Yaw, Roll values if applicable. actorRotation = rotator( actorPosition - lastPosition ); actorRotation += RAdjust; if( !bAlterPitch ) actorRotation.Pitch = lastRotation.Pitch; if( !bAlterYaw ) actorRotation.Yaw = lastRotation.Yaw; // The roll is proportional to the change in yaw (airplane turning effect) if( !bAlterRoll ) actorRotation.Roll = lastRotation.Roll; else actorRotation.Roll = 0.4*(actorRotation.Yaw - lastRotation.Yaw); PathActor.SetRotation( actorRotation ); // Save this frame's position/yaw for next frame calculations lastRotation = actorRotation; lastPosition = actorPosition; } |
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