alice-teacher Alice 3 Problems with vehicle and collisions

[Eric Brown]

James,

Thank you very much for sending us these worlds.  It has exposed numerous issues with our collision handling and setVehicle behavior (layers of exciting problems to fix).  We had been focusing on a couple of these issues as they really came to the forefront when implementing hand object collisions and pick up for VR.  This example is actually way easier for us to visualize the problem and test the fixes.  We will update when we have a better idea of what is going on and fixes on the way.  We look forwarding to sharing out a fully functional frogger game.

We greatly appreciate it when people call out these types of problems and share their worlds  with us so we can improve Alice for all.  Thank you again.

Sincerely,

Eric


> On Apr 30, 2020, at 1:21 PM, Don Slater <don at alice.org> wrote:
> 
> James,
> I will be interested to see if the community has any better ideas than mine…
> 
> I created my own version before looking at your student solution, to think about how I would do this.
> 
> Instead of using the object mover method, I used keypress listeners to have my skunk jump forward or backward a certain amount with each press.
> 
> I did use the collision-start listener to set the vehicle of the skunk to the log, which worked generally well, but there was some weirdness, I suspect because I was using the irregularly shaped log models from the gallery. Your student may have better luck using the blocks he has created.
> 
> However, instead of using a collision-end event to reset the vehicle property of my skunk, I reset that property whenever there was a keypress event, (forwards or backwards).
> 
> You may also want to play with the event optional variable “multiple event policy” (see the attached screen shot, and set it to Ignore. I had my best success with that. I have also attached “skunker.a3p” for you to examine.
> 
> I also looked back through my archives to see if I had wrestled with this before. It turns out I did, but I begged the whole question by having my critter jumping across a road dodging vehicles that were moving back and forth. Those collisions were easier to manage ;-)
> 
> Let me know how it goes…
> 
> Don Slater
> 
> Alice Project
> 
> <skunker.a3p>
> <p1.jpg>
> 
> 
>> On Apr 30, 2020, at 2:51 PM, Vanderhyde, James <vanderhyde at sxu.edu> wrote:
>> 
>> I have a student who is trying to make a Frogger-style game in Alice 3. The player needs to be able to ride logs across a river. He came up with an approach to set the vehicle of the player character to a log, when a collision event occurs. Then when the collision ends, set the vehicle back to the scene. The approach seemed sound, so I tried it in a simplified program (attached). There seems to be problems both with collision end events and with setting the vehicle. Maybe because the player character is moving?
>> 
>> I came up with a partial fix that is still unstable but works more reliably (attached). It uses a 0-length timer to check for collisions every frame, instead of using the collision event.
>> 
>> Any other suggestions? Or anywhere I should file an Alice 3 bug report?
>> 
>> James
>> —
>> James Vanderhyde
>> Associate Professor and Department Chair
>> Computer Science
>> Saint Xavier University
>> 3700 W. 103rd St.
>> Chicago, IL 60655
>> 773-298-3454
>> <collision and vehicle demo.a3p><vehicle fix.a3p>_______________________________________________
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