Car-Bicyclist Animation

Recently, a couple hours before midnight, a bicyclist suffered a medical condition that rendered him unconscious while having been riding his bicycle, according to witnesses, along the road edge of a urban street.  He collapsed off the bike and landed, according to witnesses, in the center of a street’s SB driving lane.  Sometime there after, a large automobile sedan passed over the passed-out ‘cyclist and the bicycle itself.  The driver claims that he didn’t have time to steer or brake before impact.

Animations carry with them the ability to demonstrate many explicit features of a scene’s investigation process.  Line of proximity.  Chain of Events.  Trajectory Analysis.  Line of Sight Analysis.  Visualization patterns.  Spatial & Perspective Views.  And can provide Repetitious and Visual stimuli for those reviewing the facts.

Presented here are steps necessary to project, from known facts, how this incident would appear using modern, professional Animation skills and techniques.

First, the scene is presented.  Generally, scale diagrams are used based on accurate hand-measurements or from using an electronic means (theodolite) for collecting & documenting where evidence was discovered.  One distinct advantage of using the Forensic Mapping System is its inherent ability to document 2D & 3D features of all evidence (coordinates) including the “lay of the land” (geometry) features.

In VistaFX, bring up the scene.  Seen here is how the police photos placed the traffic units at final rest.

From physical evidence, place evidence (traffic units) at their AOI or POI.

Then, one traffic unit at a time, LeftCLICK then RightCLICK and pick “Add Non-Collision Path”.

Extend RED line in the direction of the C.M. pathway to AOI or POI location, and beyond if applicable (as in this automobile’s case, as it drove some distance post impact).

Same for the ‘victim’ shape too.  L-click, then R-click … pick “Add Non-Collision Path” and extend Red line to where physical evidence, pics, or witnesses indicate.

Each traffic unit, as shown here, should now have their “motion path” (based on physical evidence) extended to the appropriate location.

Our next step is to address the motion dynamics of each “motion path”.  After picking on the initial “motion path” of the vehicle, L-click and notice the properties dialog at screen bottom.  From reconstruction efforts, indicate V1 (initial speed at start of ‘motion path’) and V2 (end of first segment of ‘motion path’).

Then from additionally, L-clicking & R-clicking on ‘motion path’ itself, choose PATH PROPERTIES …

Notice first that 2 “motion” segments are enumerated on this interactive dialog.  Note also there are two tabs labeled ‘Vehicle/Acceleration/Distance’ and ‘Rotation/Position’.  Both have purposes that will be used for animating this crash.  Note that the V1 & V2 that were input on a previous step are reflected here.  Note to yourself as well, the length of TIME (sec) for this first segment of the vehicles motion.  Why?  We’ll soon coordinate the “start” timings of the other two traffic units (body & bicycle) to commence at this time frame. 

Notice too, that the speed has been effected from the impact to final rest.  These are facts determined from your reconstruction.  Note the time for a vehicle to decelerate from a given speed to 0 (zero) speed is calculated automatically.

That finishes up the speed calculations, “motion path” and final rest position of the automobile.

The victim, obviously, was present laying flat on the street as the vehicle was moving towards it.  The victim ‘shape’ therefore must be controlled to remain ‘static’ until the vehicle passes over it, as in real life (for this incident). 

To control this, a STOPPED SEGMENT must be added.  With cursor over the ‘Segment 1’ indication, R-click and the indicated choice will be highlighted.  Pick on it and it will place itself directly over ‘segment 1’, as shown here below. 

Indicate now in the ‘Stopped segment’ the TIME that the symbol needs to remain ‘static’.  The body shape now knows how long to wait until ‘struck’, and it also has been programmed to know where to slide/rotate/roll to its final rest position.  Two segments, one with it stopped “waiting..”, and the other one where it starts from a known speed to its final stopping speed of Zero(0).

Our last traffic unit to create motion for is the bicycle.  A generic shaped “mountain bike” was used from the 3D shapes library.

This symbol originates upright, or on its two wheels.  In this case, it must be placed (rolled) onto its side.  Like the victim shape, the bike must be controlled to remain ‘static’ for a period of time.

First, to place it initially on its side, L-click, R-click and pick “Properties”.

Change the roll degree so that the handlebars appear up, resting on the roadway where physical evidence permits.  Pick “Show 3D Preview” button to see image as it will appear in the 3D animation yet come.

Next is to address the bike shape along its path, beneath the car, to its final rest position (based on physical evidence).  The approximate speed V1 and V2 also can be addressed once we L-click, R-click on “Path Properties”.

The Bike also must be controlled to remain ‘static’, as previously mentioned, and is easily accomplished by R-clicking on the ‘Segment 1’ path and inserting a STOP segment.

For this STOPPED segment, the ROLL (in degrees) must be the same 4 (!) both input values, as well as for Segment 2.

Lastly for Segment 1, modify the TIME to reflect how long it needs to be ‘static’ until Impact from the Vehicle shape.

After pressing Ok and possibly viewing it in 2D, press the “3D Animation” button and watch your work.    C O N G R A T U L A T I O N S!    J

Because it occurred at night, in this software, ambient light conditions can be modified.

Questions?  Call VistaFX direct or email me at mapscenes@aol.com

<< Back

Next >>