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<body class='hmmessage'><div dir='ltr'>1.<div>No native support in Alice 2.x to support true object collision.<div>BTW, great link about similar sized spherical collisions via Dr. James Vanderhyde (below).</div><div>With most objects there is a height, width, depth.</div><div>With sphere's the height,width,depth are the same and typically referred to as the radius.</div><div>Also with sphere's the object's origin is at the center making it easier to determine true collision.</div><div>Call the spherical objects ball1 and ball2.</div><div>Note: you cannot simply say when the distance between the balls is 0 then there is a collision when in fact they are exactly in the same 3-Dimensional position within each other ... so you need to add the lengths of the 2 (possibly different) radii to be the distance when a collision has occurred:</div><div>Create an event:</div><div>if (ball1.distance to (ball2) == (ball1.width + ball2.width))</div><div> collision = true</div><div><span style="font-size: 12pt;">else</span></div><div><div> collision = false</div></div><div><br></div><div>Note: This should be improved to not compare floating point numbers with an inequality.</div><div><div>if (ball1.distance to (ball2) <= (ball1.width + ball2.width))</div><div> collision = true</div><div><span style="font-size: 12pt;">else</span></div><div> collision = false</div></div><div> </div><div>Note: The above is for 2 spheres of any size. If you are detecting collision amongst various spheres you will have to have a more involved collection of spheres and iterate all collisions. </div><div>With 2 spheres there is 1 conditional.</div><div>With 3 spheres there are 3 conditionals (1+2). </div><div>With 4 spheres there are 6 conditionals (1+2+3). </div><div><div>With 5 spheres there are 10 conditionals (1+2+3+4). </div></div><div>With N spheres there are (1+2+3+ ... + N-1) <span style="font-size: 12pt;">conditionals.</span></div><div><br></div><div>Note: This becomes more involved with non-spherical objects where the orientation of the two objects along with their components of height, width, and depth between the two objects becomes important.</div><div><br></div><div><span style="font-size: 12pt;">2.</span></div><div>Assuming you still want the cursor keys to control the movement of an object (call it personJoe) forward-back-left-right and other keys for up-down:</div><div>[a] Create a variable to control personJoe's speed (assume uniform speed in all six directions), call it distancePerCursorClick, initialize it to 0</div><div>[b] <span style="font-size: 12pt;">Create an event b</span><span style="font-size: 12pt;">ound</span> to the 'S' key to decrease personJoe's speed:</div><div>distancePerCursorClick = <span style="font-size: 12pt;">distancePerCursor</span><span style="font-size: 12pt;">Click - 1</span></div><div>[c]<span style="font-size: 12pt;"> </span><span style="font-size: 12pt;">Create an event b</span><span style="font-size: 12pt;">ound</span><span style="font-size: 12pt;"> </span><span style="font-size: 12pt;">to the 'F' key to increase personJoe's speed:</span></div><div>distancePerCursorClick = <span style="font-size: 12pt;">distancePerCursor</span><span style="font-size: 12pt;">Click + 1</span></div><div>[d] <span style="font-size: 12pt;">Create an event for each of the six cursor keys similar to this:</span></div><div>When the up cursor is clicked</div><div><span style="font-size: 12pt;"> move </span>personJoe<span style="font-size: 12pt;"> up by the distance </span>distancePerCursorClick</div><div>Note: you can package this idea anyway you want, but this is the basic idea.</div><div>Note: be careful that repeated clicking of the 'S' key can make the distancePerCursorClick become negative and hence your movement keys will make personJoe act backwards from the clicked cursor key </div><div><br></div><div>Not: you do not have to have uniform speed in all directions. In this case, create three variables:</div><div><div>distancePerUpDownCursorClick</div></div><div><div>distancePerLeftRightCursorClick</div></div><div><div>distancePerForwardBackCursorClick</div></div><div><br></div><div>--Ed Bujak</div><div><br></div><div><div><hr id="stopSpelling">From: jvanderhyde@benedictine.edu<br>To: alice-teachers@lists.andrew.cmu.edu<br>Date: Thu, 5 Sep 2013 13:28:28 +0000<br>Subject: Re: alice-teacher Collision and walking speed questions<br><br>
1. Collision detection in Alice is tricky. I have had students try several different approaches, but nothing has really worked as well as I would like. There are some tutorials you can read (I found it with a Google search):
<div><a href="http://programminginalice.wordpress.com/tag/collision-detection/" target="_blank">http://programminginalice.wordpress.com/tag/collision-detection/</a></div>
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<div>2. I don't think there's any way to modify those existing controls, so you have to write your own controls for the player object. One non-obvious feature that will be useful is that you can right-click on events (such as "when a key is typed") and change
it to something else ("while a key is pressed").</div>
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<div>James<br>
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<div>Dr. James Vanderhyde</div>
<div>Math and Computer Science</div>
<div>Benedictine College</div>
<div><a href="mailto:jvanderhyde@benedictine.edu">jvanderhyde@benedictine.edu</a></div>
<div><a href="http://vanderhyde.us/~james/pro/" target="_blank">http://vanderhyde.us/~james/pro/</a></div>
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<div>On Sep 4, 2013, at 12:46 PM, Lori Fuller <<a href="mailto:lori.fuller@browardschools.com">lori.fuller@browardschools.com</a>> wrote:</div>
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<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">I have an advanced student among all of my beginners... and he is working on a maze game.</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">2 questions:</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">1. In Alice 2.3, is it possible to set up a collision indication method? If so, where do I find information on this?</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">2. Is there a way to slow down the person object walking while using the arrow keys as controllers?</font></div>
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<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">thanks,</font></div>
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<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Lori Fuller, M.Ed.</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Monarch High School</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Career Technology Department Head</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Technology Coordinator</font></div>
<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Asst. Athletic Director</font></div>
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<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">"A posse ad esse", from possibility to actuality...</font></div>
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<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Big brother is watching so watch what you put in the email!</font></div>
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<div align="left" style="text-align:left;"><font face="Times New Roman" size="+1" style="font-family:'Times New Roman';font-size:14pt;">Under Florida law, e-mail addresses, and all communications, including e-mail communications, made or received in connection
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