Questions on HW6-Spring07

Questions on HW6-Spring07

HW6 is due on March 14. Mark Guzdial.

TO BE COMPLETELY CLEAR: IF YOU DO NOT HAVE A PARTNER FOR HW6, YOU WILL LOSE 10 POINTS. Period. There have been lots of recitation sessions where you could go meet a partner. I'm certainly getting lots of email on this question, so there are lots of peole without partners. You must have a partner – and your code must represent each partner's work 50-50 and we must have a signed statement agreeing to that. We've been talking about this for weeks, it's been here on the CoWeb. No partner == one letter grade drop. Mark Guzdial

Question: How can I change the number of frames per second that my animation plays? Right now it's playing one frame every 5 seconds or so.

  /**
   * Method to replay the frames (pictures) added so far
   * @param sleepTime the amount to sleep in milliseconds
   * between frames
   */
  public void replay(int sleepTime)

The only thing I can think of off the top of my head is to use replay and change the sleep time to a lower number. Dawn Finney

Question: When I run my animation , I get this error: OutOfMemoryError: Java heap space
Why the heck does it give me this error. It runs the animation for about 10 frames, and then it gives me the error.

I'm thinking that either your frames are too big for your computer to handle or that you have an infinite loop somewhere. Dawn Finney.

Question: In my animation I want to use LayeredSceneElements so that I can layer my pictures in my animation (say I want something appear to walk behind an object in the picture). Can I use LayeredSceneElement in a tree? It seems to me that I should be able to use it by making the linked list and inserting the entire list as one child to a branch. Because the branch understands ‘addchild’ it doesn’t matter what I make as a child does it?

Right now I am basically wanting to use LayeredSceneElement to position my pictures on a background, then render the background, then move some of the layered scene elements a little bit and then re-render, etc. My Problem is that I am not exactly sure how this would fit into a tree with branches and such. I mean why do I need a root and branches and such if I can just use a FrameSequence of a bunch of LayeredSceneElements?

What a great question! The point of the tree is to be able to structure branches into conceptually related pieces – here's the village, here's the forest, etc. Yes, you can certainly do it all with a linked list, but you can't cluster the pieces. To get what you want:
- Use a MoveBranch to place things where you want.
- The ordering of the tree branches left-to-right will decide what gets drawn first, second...last. Whatever part you want to be behind the other parts, add that branch to the tree first. Since we traverse the branches left to right, the first branches will get drawn "beneath" the others.
Mark Guzdial

Question: I am trying to get the sounds to play with the animation and am trying to figure a few things out. I made a linked list of sound nodes in the setup on the animation that corresponds with the number of frames the animation contains. I did this because I wanted to play one node with each frame and then when the frame changes and re-renders the next sound plays etc. The problem I am encountering is playing only a single sound node. playFromMeOn() plays the entire linked list. I was wondering how I could say current = first sound node, play that node, then current=current.getNext().

You can use SoundElement to create a linked list of Sounds and move through the list like you describe. The you could just do current.play() to play the individual Sound. Dawn Finney.

You said that if you use SoundElement to create a linked list of Sounds you could use current.play() to play the individual sound. I am still getting an error saying that the method play() is not in SoundElement: any ideas?

cannot find symbol
symbol  : method play()
location: class SoundElement

Yeah sorry. I meant to say current.getSound().play();. Dawn Finney.

Question: When I try to play my AnimationRunner, I get the error "NullPointerException", and then refers to line 108, which is where we first try to move an object. All of the code compiles, and everything before that (setUp and renderScene) works. What does that error mean, and what are ways that we can fix it? Thanks!

It's hard to say what is the problem is here, because your line 108 is more than likely different from mine. Just because your program compiles, it doesn't mean that it'll work properly. The Java compiler only catches syntax errors for you. Exceptions like the NullPointerException occur when you have some problem with your logic. My guess is that when you are trying to move an object, no object is actually there to be moved, which means you probably set up your data structure incorrectly. Dawn Finney.

(Referring to the previous question) I think we have an object to move, because when we render just one frame, it works (all the pictures come up, etc.) It's just when we try to move this first object/picture the first time and we get a NullPointerException. Do we have to do casting anywhere in our code? We pretty much followed the wolfattackmovie, and there wasn't any in there....

I really don't see how casting factors into this. Honestly there could be a million things wrong. It easier and faster way to do this is for you to post the line that is giving you Exceptions (the entire line not the number). The easiest and fastest way for the both of us would be for you to email your code to me and let me see for myself. PLEASE STOP SENDING ME YOUR CODE IF YOU HAVE A nullPointerException. I only meant for her to send me her code because her description of her code was inconsistent with a nullPointerException.Dawn Finney

Question: frames = new FrameSequence("C:/Temp/"); Why is this line in our wolf attack movie? if we're using wolf-attack movie as a template, what should this line be replaced with (if it needs to be replaced at all)?

It puts all of the frames into the C:/Temp/ folder on your computer. It doesn't need to be changed if you don't want to. Dawn Finney.

Question: Is there a way we can change the amount of java heap space for memory in Dr. Java?

Don't think so. Dawn Finney.
I don't think Dr. Java will let you do it, but if you want to run from the command line you can use the argument java -Xmx512m MyClass . You'll have to do a lot of other stuff to get all the classpaths set up if you want to use java from a command prompt, so it may not be worth it for you. A link to command line arguments http://java.sun.com/j2se/1.5.0/docs/tooldocs/windows/java.html. Joel Uthe

Question: On the question about the Drjava heap space... do you know where in the book it explains how to do add more? I know I have read it somewhere, but now I can't find it.

No clue, but your program really shouldn't be using all of Java's heap space anyway. Dawn Finney.
I don't know what page it is on, but there is a way to do it. Put the arguments -Xmx32m in JVM Arguments for Interactions JVM in Edit>Preferences>Miscellaneous where 32m stands for 32 megabytes. it must be a power of 2 and either m(mega) or k(kilo) bytes. Dawn is correct though, your program shouldn't be using all of Java's default heap space, and your TA's WILL NOT GRADE WITH AN INCREASED HEAP SPACE even if you ask them to. Joel Uthe

Question: What's the best way to outline a picture? For instance, I have a picture that I want to show on a background, but when I put it on the background the white space of the picture shows up. Do you know of any program that will allow me to save a picture without all of the extra white space?

Photoshop, but it takes skill. I would get the animation up and running before worrying about aesthetics. Dawn Finney.

Question: Turn in ALL the classes that you're using for your data structures. (You don't have to turn in Picture, Sound, FrameSequence, or its related structures (unless you've changed them), but everything you're using for keeping your sound list and scene structure.)
That above is what the hw description says. So, if I didn't modify SoundElement or ScaleBranch, would I still turn them in? Or, is this referring to those people who have set up their linked lists in another class aside from the AnimationRunner class. Could you please provide clarification on what this is asking. According to my interpretation, I didn't manipulate any other classes, even though I called an instance of them like scaleBranch, so I would only turn in my AnimationRunner class.

Look below. Dawn Finney.

Question: Yeah I have the same question as the one above. Would we turn in things like Branch.java, MoveBranch.java, BlueScreenNode.java, etc. even if we didn't modify them?

Why would you turn in classes that your TA already has if you didn't modify them? Turn classes that you manipulated from the java sources folder and any other classes you created for use in AnimationRunner. Dawn Finney.

Question: when using songNode or songBranch when we play the list of sounds, the sounds are streched and play slowly... how can we fix that?

There is a handy dandy scale function that all sounds know... why don't you use that?? -Fellow Student

Question: I can't seem to make my linked list of sounds work. I did SoundElement current = splash1 (my first sound node), current.getSound().play(), then current=current.getNext() but I can't get the for loop cintaing my frames and this code to cycle through my Sounds. What do I need to do instead?

What's cintaing? Dawn Finney.

lol, sorry my typing sucks. I meant containing but nevermind anyway. My partner figured it out.

Question: I want to have a picture come in from the top of the screen. For example, say I wanted to animate a skydiver falling, and I wanted to show him entering the screen from the top (seeing his feet, his legs, his torso, etc...) and leaving the screen at the bottom (no longer seeing his feet, no longer seeing his legs...). I know how to show him leaving the screen, because you can just insert the picture progressively lower, but I can't figure out how to show him entering the screen. Any suggestions?

You can start him off the screen and have him slowly enter. Coordinate (0,0) is the UpperLeft corner in java. You'll have to make him be less than (0,0) -Joel Uthe

Question: I tried entering in negative coordinates and I got an out of bounds error. Is that what you meant by making him be less than (0,0). What am I not doing?

I have no clue what Joel is talking. Sorry. Dawn Finney.

Class is moved to Management 102 on Friday 10-11 am. The Architecture auditorium is going to be used for the memorial service for Dean Tom Galloway. Mark Guzdial

BTW, getSound().play() works, but so does .blockingPlay() and .playSound() in SoundElement. Mark Guzdial

Question: If we do getSound.play(), can we tell the playback to stop at a certain point? For instance, after we've done a certain number of frames, we want the playback to stop no matter what; is that possible?

Use an if statement and break. Dawn Finney.
We actually don't have a way to stop the current sound playback. I suggest breaking your sound into separate pieces, store them in separate files, then use them in separate nodes of the linked list. Then you have finer grained control of the sound. Mark Guzdial

Question: There is a time in out animation (towards the end) where we have a picture that we want to remove and another one to add. We have the this.root().remove(....) and this.root().addChild(...), but when we run the animation, the picture that we want to remove doesn't go away. In previous times that we removed pictures, they went away. Why is that picture not going away????

My bet is that you're trying to remove the first branch in the tree. You may not recall us talking about this in class – that our current implementation of trees and lists does not allow for deletion of the first item in the list? Move it further down the list – make something else the first child. Mark Guzdial

Question: what was the avg for test 2?

We don't know yet. (Asking the question on a different page doesn't change the answer :-) Mark Guzdial

Question: Looking at the homework criteria it says that we will be penalized if we only use one or two types of sound. What is meant by types of sound? This means we have to use multiple "types" of sound? Please explain.

Different sounds are sounds that sound different. Dawn Finney.

Question: the criteria states that we have to have at least 5 nodes in our sound linkedList... can some of these nodes be rests? And to create our linkedList using sound elements can we treat them as sound nodes

"Create another list with the sounds to be played during the animation of this tree. (Sounds could be a rest!)," from Homework 6 description. Yes SoundElement and SoundNode are both REMOVEDkedLists just with different data. You can basically treat them the same. Dawn Finney.

Question: how would i play this list of sounds? Thank You!

Answered before. Look somewhere above. Dawn Finney.

Question: Do we need to turn in MoveBranch, HBranch, BlueScreenNode, and SoundElement if we did not change them at all???

STOP ASKING THIS!!!! Dawn Finney.

I am getting a null pointer exception. I tried running wam.renderScene() after setting wam to be a new WolfAttackMovie, just to see if it would work with code I didn't write, but I get the same error. Any help?

Nevermind. I was forgetting to setUp() first.

Link to this Page

Homeworks-Spring 2007 last edited on 19 April 2007 at 10:45 pm by c-76-17-114-206.hsd1.ga.comcast.net