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• Implementing a Custom Coherence PartitionAssignmentStrategy

  - by jpurdy

  A recent A-Team engagement required the development of a custom PartitionAssignmentStrategy (PAS). By way of background, a PAS is an implementation of a Java interface that controls how a Coherence partitioned cache service assigns partitions (primary and backup copies) across the available set of storage-enabled members. While seemingly straightforward, this is actually a very difficult problem to solve. Traditionally, Coherence used a distributed algorithm spread across the cache servers (and as of Coherence 3.7, this is still the default implementation). With the introduction of the PAS interface, the model of operation was changed so that the logic would run solely in the cache service senior member. Obviously, this makes the development of a custom PAS vastly less complex, and in practice does not introduce a significant single point of failure/bottleneck. Note that Coherence ships with a default PAS implementation but it is not used by default. Further, custom PAS implementations are uncommon (this engagement was the first custom implementation that we know of). The particular implementation mentioned above also faced challenges related to managing multiple backup copies but that won't be discussed here. There were a few challenges that arose during design and implementation: Naive algorithms had an unreasonable upper bound of computational cost. There was significant complexity associated with configurations where the member count varied significantly between physical machines. Most of the complexity of a PAS is related to rebalancing, not initial assignment (which is usually fairly simple). A custom PAS may need to solve several problems simultaneously, such as: Ensuring that each member has a similar number of primary and backup partitions (e.g. each member has the same number of primary and backup partitions) Ensuring that each member carries similar responsibility (e.g. the most heavily loaded member has no more than one partition more than the least loaded). Ensuring that each partition is on the same member as a corresponding local resource (e.g. for applications that use partitioning across message queues, to ensure that each partition is collocated with its corresponding message queue). Ensuring that a given member holds no more than a given number of partitions (e.g. no member has more than 10 partitions) Ensuring that backups are placed far enough away from the primaries (e.g. on a different physical machine or a different blade enclosure) Achieving the above goals while ensuring that partition movement is minimized. These objectives can be even more complicated when the topology of the cluster is irregular. For example, if multiple cluster members may exist on each physical machine, then clearly the possibility exists that at certain points (e.g. following a member failure), the number of members on each machine may vary, in certain cases significantly so. Consider the case where there are three physical machines, with 3, 3 and 9 members each (respectively). This introduces complexity since the backups for the 9 members on the the largest machine must be spread across the other 6 members (to ensure placement on different physical machines), preventing an even distribution. For any given problem like this, there are usually reasonable compromises available, but the key point is that objectives may conflict under extreme (but not at all unlikely) circumstances. The most obvious general purpose partition assignment algorithm (possibly the only general purpose one) is to define a scoring function for a given mapping of partitions to members, and then apply that function to each possible permutation, selecting the most optimal permutation. This would result in N! (factorial) evaluations of the scoring function. This is clearly impractical for all but the smallest values of N (e.g. a partition count in the single digits). It's difficult to prove that more efficient general purpose algorithms don't exist, but the key take away from this is that algorithms will tend to either have exorbitant worst case performance or may fail to find optimal solutions (or both) -- it is very important to be able to show that worst case performance is acceptable. This quickly leads to the conclusion that the problem must be further constrained, perhaps by limiting functionality or by using domain-specific optimizations. Unfortunately, it can be very difficult to design these more focused algorithms. In the specific case mentioned, we constrained the solution space to very small clusters (in terms of machine count) with small partition counts and supported exactly two backup copies, and accepted the fact that partition movement could potentially be significant (preferring to solve that issue through brute force). We then used the out-of-the-box PAS implementation as a fallback, delegating to it for configurations that were not supported by our algorithm. Our experience was that the PAS interface is quite usable, but there are intrinsic challenges to designing PAS implementations that should be very carefully evaluated before committing to that approach.

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• Smooth animation on QStackedWidget

  - by saravanan

  Hi., i have five Qwidgets (Each QWidget having different controls). i put all the QWidget into one Parent QStackedWidget. for change the display of Qwidget i am using setCurrentIndex(int) function. There is no problem in displaying. but i need to put animation while changing the page. i tried nothing is working. so i removed the QStackedWidget and i put QWidget directly and i tried with QPropertyAnimation. This QPropertyAnimation is working but it's not the smooth animation. Here my code for QPropertyAnimation. QRect pGeo(8,152,width()-16,height()-160); profilePage->show(); //first QWidget QPropertyAnimation *anim1= new QPropertyAnimation(profilePage, "geometry"); anim1->setStartValue(QRect(200,pGeo.y(),pGeo.width(),pGeo.height())); anim1->setEndValue(pGeo); anim1->setEasingCurve(QEasingCurve::InOutSine); anim1->setDuration(500); anim1->start(); how to do the smooth animation using the QWidget or the QStackedWidget. Please give some suggestion to implement the smooth animation.

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• Runge-Kutta (RK4) integration for game physics

  - by Kai

  Gaffer on Games has a great article about using RK4 integration for better game physics. The implementation is straightforward but the math behind it confuses me. I understand derivatives and integrals on a conceptual level but I haven't manipulated equations in a long time. Here's the brunt of Gaffer's implementation: void integrate(State &state, float t, float dt) { Derivative a = evaluate(state, t, 0.0f, Derivative()); Derivative b = evaluate(state, t+dt*0.5f, dt*0.5f, a); Derivative c = evaluate(state, t+dt*0.5f, dt*0.5f, b); Derivative d = evaluate(state, t+dt, dt, c); const float dxdt = 1.0f/6.0f * (a.dx + 2.0f*(b.dx + c.dx) + d.dx); const float dvdt = 1.0f/6.0f * (a.dv + 2.0f*(b.dv + c.dv) + d.dv) state.x = state.x + dxdt * dt; state.v = state.v + dvdt * dt; } Can anybody explain in simple terms how RK4 works? Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? After reading the accepted answer below, and several other articles, I have a grasp on how RK4 works. To answer my own questions: Can anybody explain in simple terms how RK4 works? RK4 takes advantage of the fact that we can get a much better approximation of a function if we use its higher-order derivatives rather than just the first or second derivative. That's why the Taylor series converges much faster than Euler approximations. (take a look at the animation on the right side of that page) Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? The Runge-Kutta method is an approximation of a function that samples derivatives of several points within a timestep, unlike the Taylor series which only samples derivatives of a single point. After sampling these derivatives we need to know how to weigh each sample to get the closest approximation possible. An easy way to do this is to pick constants that coincide with the Taylor series, which is how the constants of a Runge-Kutta equation are determined. This article made it clearer for me: http://web.mit.edu/10.001/Web/Course%5FNotes/Differential%5FEquations%5FNotes/node5.html. Notice how (15) is the Taylor series expansion while (17) is the Runge-Kutta derivation. How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? Mathematically it converges much faster than doing many Euler approximations. Of course, with enough Euler approximations we can gain equal accuracy to RK4, but the computational power needed doesn't justify using Euler.

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• WPF zoom canvas and maintain scroll position

  - by Alex McBride

  I have a Canvas element, contained within a ScrollViewer, which I'm zooming using ScaleTransform. However, I want to be able to keep the scroll position of the viewer focused on the same part of the canvas after the zoom operation has finished. Currently when I zoom the canvas the scroll position of the viewer stays where it was and the place the user was viewing is lost. I'm still learning WPF, and I've been going backwards and forwards a bit on this, but I can't figure out a nice XAML based way to accomplish what I want. Any help in this matter would be greatly appreciated and would aid me in my learning process. Here is the kind of code I'm using... <Grid> <ScrollViewer Name="TrackScrollViewer" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto"> <Canvas Width="2560" Height="2560" Name="TrackCanvas"> <Canvas.LayoutTransform> <ScaleTransform ScaleX="{Binding ElementName=ZoomSlider, Path=Value}" ScaleY="{Binding ElementName=ZoomSlider, Path=Value}"/> </Canvas.LayoutTransform> <!-- Some complex geometry describing a motor racing circuit --> </Canvas> </ScrollViewer> <StackPanel Orientation="Horizontal" Margin="8" VerticalAlignment="Top" HorizontalAlignment="Left"> <Slider Name="ZoomSlider" Width="80" Minimum="0.1" Maximum="10" Value="1"/> <TextBlock Margin="4,0,0,0" VerticalAlignment="Center" Text="{Binding ElementName=ZoomSlider, Path=Value, StringFormat=F1}"/> </StackPanel> </Grid>

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• rand() generating the same number – even with srand(time(NULL)) in my main!

  - by Nick Sweet

  So, I'm trying to create a random vector (think geometry, not an expandable array), and every time I call my random vector function I get the same x value, thought y and z are different. int main () { srand ( (unsigned)time(NULL)); Vector<double> a; a.randvec(); cout << a << endl; return 0; } using the function //random Vector template <class T> void Vector<T>::randvec() { const int min=-10, max=10; int randx, randy, randz; const int bucket_size = RAND_MAX/(max-min); do randx = (rand()/bucket_size)+min; while (randx <= min && randx >= max); x = randx; do randy = (rand()/bucket_size)+min; while (randy <= min && randy >= max); y = randy; do randz = (rand()/bucket_size)+min; while (randz <= min && randz >= max); z = randz; } For some reason, randx will consistently return 8, whereas the other numbers seem to be following the (pseudo) randomness perfectly. However, if I put the call to define, say, randy before randx, randy will always return 8. Why is my first random number always 8? Am I seeding incorrectly?

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• Images missing after moving Django to new server

  - by miszczu

  I'm moving Django project to new server. I'm newbie in Django, and I don't know where should be upload folder. There are all images which should be displayed on website. In config file I haven't seen upload folder I could specify, so I'm guessing it always should be the same location for django projects or I just can't find it. Locations are saved in database. When I've put uploaded files into media folder, so url was like domain.co.uk/media/upload/media/images/year/month/day/image_name.ext and the same is on the old website, images on website ware still missing. All images are visible if I put url by hand, but django doesn't seems to see files. Also I check django log file: 2012-05-30 09:13:33,393 ERROR render: Thumbnail tag failed: [in /usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/templatetags/thumbnail.py (line 49)] Traceback (most recent call last): File "/usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/templatetags/thumbnail.py", line 45, in render return self._render(context) File "/usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/templatetags/thumbnail.py", line 97, in _render file_, geometry, **options File "/usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/base.py", line 50, in get_thumbnail cached = default.kvstore.get(thumbnail) File "/usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/kvstores/base.py", line 25, in get return self._get(image_file.key) File "/usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/kvstores/base.py", line 123, in _get value = self._get_raw(add_prefix(key, identity)) File "/usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/kvstores/cached_db_kvstore.py", line 26, in _get_raw value = KVStoreModel.objects.get(key=key).value File "/usr/lib/python2.6/site-packages/django/db/models/manager.py", line 132, in get return self.get_query_set().get(*args, **kwargs) File "/usr/lib/python2.6/site-packages/django/db/models/query.py", line 344, in get num = len(clone) File "/usr/lib/python2.6/site-packages/django/db/models/query.py", line 82, in __len__ self._result_cache = list(self.iterator()) File "/usr/lib/python2.6/site-packages/django/db/models/query.py", line 273, in iterator for row in compiler.results_iter(): File "/usr/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 680, in results_iter for rows in self.execute_sql(MULTI): File "/usr/lib/python2.6/site-packages/django/db/models/sql/compiler.py", line 735, in execute_sql cursor.execute(sql, params) File "/usr/lib/python2.6/site-packages/django/db/backends/util.py", line 34, in execute return self.cursor.execute(sql, params) File "/usr/lib/python2.6/site-packages/django/db/backends/mysql/base.py", line 86, in execute return self.cursor.execute(query, args) File "/usr/lib64/python2.6/site-packages/MySQLdb/cursors.py", line 174, in execute self.errorhandler(self, exc, value) File "/usr/lib64/python2.6/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler raise errorclass, errorvalue DatabaseError: (1146, "Table 'thumbnail_kvstore' doesn't exist") 2012-05-30 09:13:33,396 DEBUG execute: (0.000) SELECT `freetext_freetext`.`id`, `freetext_freetext`.`key`, `freetext_freetext`.`content`, `freetext_freetext`.`active` FROM `freetext_freetext` WHERE (`freetext_freetext`.`active` = True AND `freetext_freetext`.`key` = office-closed-message ); args=(True, u'office-closed-message') [in /usr/lib/python2.6/site-packages/django/db/backends/util.py (line 44)] 2012-05-30 09:13:33,399 DEBUG execute: (0.000) SELECT `menus_menu`.`id`, `menus_menu`.`name`, `menus_menu`.`slug`, `menus_menu`.`base_url`, `menus_menu`.`description`, `menus_menu`.`enabled` FROM `menus_menu` WHERE (`menus_menu`.`enabled` = True AND `menus_menu`.`slug` = about ); args=(True, u'about') [in /usr/lib/python2.6/site-packages/django/db/backends/util.py (line 44)] 2012-05-30 09:13:33,401 DEBUG execute: (0.000) SELECT `menus_menuitem`.`id`, `menus_menuitem`.`menu_id`, `menus_menuitem`.`title`, `menus_menuitem`.`url`, `menus_menuitem`.`order` FROM `menus_menuitem` INNER JOIN `menus_menu` ON (`menus_menuitem`.`menu_id` = `menus_menu`.`id`) WHERE `menus_menu`.`slug` = about ORDER BY `menus_menuitem`.`order` ASC; args=(u'about',) [in /usr/lib/python2.6/site-packages/django/db/backends/util.py (line 44)] 2012-05-30 09:13:33,404 DEBUG execute: (0.000) SELECT `freetext_freetext`.`id`, `freetext_freetext`.`key`, `freetext_freetext`.`content`, `freetext_freetext`.`active` FROM `freetext_freetext` WHERE (`freetext_freetext`.`active` = True AND `freetext_freetext`.`key` = contactdetails-footer ); args=(True, u'contactdetails-footer') [in /usr/lib/python2.6/site-packages/django/db/backends/util.py (line 44)] I checked database and there is no table calls thumbnail_kvstore, but I have database backup, and in backup files this table doesn't exist. All uploaded files I get are in media/uploads/media/. Also I'm getting errors on some pages: Syntax error. Expected: ``thumbnail source geometry [key1=val1 key2=val2...] as var`` /usr/lib/python2.6/site-packages/sorl_thumbnail-11.12-py2.6.egg/sorl/thumbnail/templatetags/thumbnail.py in __init__, line 72 In template /var/www/vhosts/domain.co.uk/sites/apps/shop/products/templates/products/product_detail.html, error at line 34 {% thumbnail image.file "800x700" detail as zoom %} Maybe some modules I install are not in the right version. Dont know how to fix it. Im using, CentOS 6, mod_wsgi, apache, python 2.6. Update 1.0: On the old server was Django 1.3, on the new one is Django 1.3.1 Update 1.1: I this i know where is the problem. I tried python manage.py syncdb and this is output: Syncing... Creating tables ... The following content types are stale and need to be deleted: orders | ordercontact Any objects related to these content types by a foreign key will also be deleted. Are you sure you want to delete these content types? If you're unsure, answer 'no'. Type 'yes' to continue, or 'no' to cancel: no Installing custom SQL ... Installing indexes ... No fixtures found. Synced: > django.contrib.auth > django.contrib.contenttypes > django.contrib.sessions > django.contrib.sites > django.contrib.messages > django.contrib.admin > django.contrib.admindocs > django.contrib.markup > django.contrib.sitemaps > django.contrib.redirects > django_filters > freetext > sorl.thumbnail > django_extensions > south > currencies > pagination > tagging > honeypot > core > faq > logentry > menus > news > shop > shop.cart > shop.orders Not synced (use migrations): - dbtemplates - contactform - links - media - pages - popularity - testimonials - shop.brands - shop.collections - shop.discount - shop.pricing - shop.product_types - shop.products - shop.shipping - shop.tax (use ./manage.py migrate to migrate these) Next I run python manage.py migrate, and thats what i get: Running migrations for dbtemplates: - Migrating forwards to 0002_auto__del_unique_template_name. > dbtemplates:0001_initial ! Error found during real run of migration! Aborting. ! Since you have a database that does not support running ! schema-altering statements in transactions, we have had ! to leave it in an interim state between migrations. ! You *might* be able to recover with: = DROP TABLE `django_template` CASCADE; [] = DROP TABLE `django_template_sites` CASCADE; [] ! The South developers regret this has happened, and would ! like to gently persuade you to consider a slightly ! easier-to-deal-with DBMS. ! NOTE: The error which caused the migration to fail is further up. Traceback (most recent call last): File "manage.py", line 13, in <module> execute_manager(settings) File "/usr/lib/python2.6/site-packages/django/core/management/__init__.py", line 438, in execute_manager utility.execute() File "/usr/lib/python2.6/site-packages/django/core/management/__init__.py", line 379, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/usr/lib/python2.6/site-packages/django/core/management/base.py", line 191, in run_from_argv self.execute(*args, **options.__dict__) File "/usr/lib/python2.6/site-packages/django/core/management/base.py", line 220, in execute output = self.handle(*args, **options) File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/management/commands/migrate.py", line 105, in handle ignore_ghosts = ignore_ghosts, File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/__init__.py", line 191, in migrate_app success = migrator.migrate_many(target, workplan, database) File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/migrators.py", line 221, in migrate_many result = migrator.__class__.migrate_many(migrator, target, migrations, database) File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/migrators.py", line 292, in migrate_many result = self.migrate(migration, database) File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/migrators.py", line 125, in migrate result = self.run(migration) File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/migrators.py", line 99, in run return self.run_migration(migration) File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/migrators.py", line 81, in run_migration migration_function() File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/migration/migrators.py", line 57, in <lambda> return (lambda: direction(orm)) File "/usr/lib/python2.6/site-packages/django_dbtemplates-1.3-py2.6.egg/dbtemplates/migrations/0001_initial.py", line 18, in forwards ('last_changed', self.gf('django.db.models.fields.DateTimeField')(default=datetime.datetime.now)), File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/db/generic.py", line 226, in create_table ', '.join([col for col in columns if col]), File "/usr/lib/python2.6/site-packages/South-0.7.3-py2.6.egg/south/db/generic.py", line 150, in execute cursor.execute(sql, params) File "/usr/lib/python2.6/site-packages/django/db/backends/util.py", line 34, in execute return self.cursor.execute(sql, params) File "/usr/lib/python2.6/site-packages/django/db/backends/mysql/base.py", line 86, in execute return self.cursor.execute(query, args) File "/usr/lib64/python2.6/site-packages/MySQLdb/cursors.py", line 174, in execute self.errorhandler(self, exc, value) File "/usr/lib64/python2.6/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler raise errorclass, errorvalue _mysql_exceptions.OperationalError: (1050, "Table 'django_template' already exists") Also i run python manage.py migrate --list, and uotput is: dbtemplates (*) 0001_initial (*) 0002_auto__del_unique_template_name contactform (*) 0001_initial (*) 0002_auto__add_callback (*) 0003_auto__add_field_callback_notes (*) 0004_auto__add_field_callback_is_closed__add_field_callback_closed (*) 0005_auto__add_field_callback_url (*) 0006_auto__add_contact (*) 0007_auto__add_field_contact_category (*) 0008_auto__add_field_contact_url links (*) 0001_initial (*) 0002_auto__add_field_category_enabled__add_field_category_order media (*) 0001_initial (*) 0002_auto__del_field_image_external_url__add_field_image_link_url__del_fiel (*) 0003_add_model_FileAttachment (*) 0004_auto__chg_field_file_slug__chg_field_image_slug (*) 0005_auto__chg_field_image_file (*) 0006_auto__chg_field_file_file pages (*) 0001_initial (*) 0002_auto__chg_field_page_meta_description__chg_field_page_meta_title__chg_ (*) 0003_auto__add_field_page_show_in_sitemap (*) 0004_auto__add_field_page_changefreq__add_field_page_priority popularity (*) 0001_initial testimonials (*) 0001_initial (*) 0002_auto__add_field_testimonial_is_featured brands (*) 0001_initial (*) 0002_auto__add_field_brand_template (*) 0003_auto__chg_field_brand_meta_description__chg_field_brand_meta_title__ch (*) 0004_auto__add_field_brand_url (*) 0005_auto__del_field_brand_image__add_field_brand_logo collections (*) 0001_initial (*) 0002_auto__add_field_collection_discount (*) 0003_auto__chg_field_collection_meta_description__chg_field_collection_meta (*) 0004_auto__add_field_collection_is_featured (*) 0005_auto__add_field_collection_order discount (*) 0001_initial (*) 0002_added_field_discount_description (*) 0003_auto__add_field_discountvoucher_automatic (*) 0004_auto__add_field_discountvoucher_collection (*) 0005_auto__del_field_discountvoucher_collection (*) 0006_auto__chg_field_discountvoucher_expiry_date pricing (*) 0001_initial (*) 0002_auto__add_pricingrule product_types (*) 0001_initial (*) 0002_auto__add_field_producttype_meta_title__add_field_producttype_meta_des (*) 0003_auto__add_field_producttype_summary__add_field_producttype_description products (*) 0001_initial (*) 0002_auto__del_field_product_is_featured (*) 0003_auto__chg_field_product_meta_keywords__chg_field_product_meta_descript (*) 0004_auto shipping (*) 0001_initial (*) 0002_auto__add_field_shippingmethod_includes_tax__add_field_shippingmethod_ (*) 0003_auto__add_field_shippingmethod_order (*) 0004_auto__del_field_shippingmethod_tax_rate__del_field_shippingmethod_incl (*) 0005_auto__del_field_shippingrule_enabled tax (*) 0001_initial (*) 0002_auto__add_field_taxrate_internal_name (*) 0003_initial_internal_names (*) 0004_auto__add_unique_taxrate_internal_name (*) 0005_force_unique_taxrate_name (*) 0006_auto__add_unique_taxrate_name After that some images source were something like this: src="cache/1e/bd/1ebd719910aa843238028edd5fe49e71.jpg" Is any1 could help me with syncdb pledase?

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• Getting a job in the games industry as a developer, just knowing a game engine

  - by numerical25

  I recently enrolled in a community college for games developement. But I am skeptical about the curriculum. I have no experience in the gaming industry so I wouldn't be able to tell whether it's a good investment or not. So I am asking you. I don't want to get too much into the details of all the classes I am taking so I will try to be brief. By the time I graduate, I should have a understanding of how a game engine works. I will be working with the Unreal Engine to develop a Multiplayer game from scratch. So in the process of my final project, I will learn how to work within the Unreal Engine, learn Python and learn how to use its API to connect to a remote server and build game mechanics. Overall I will also recieve an associates degree in game development. I learn C++ but not C. The director said he was trying to implement C in the program as well. What I notice is I will not learn how to build a 3D game engine from scratch. They do not teach any artificial intelligence (AI). I will not learn how to work with the graphics card using a graphics API such as DirectX or OpenGL. I know building a game engine from scratch is a little complex, but at the same time the track is requiring me to take some advanced mathematics courses such as calculus and geometry 1 and 2. I also got to take a physics class. I just think that's a little much for just learning how to use the Unreal Engine but not actually build one or try to learn the anatomy of a games engine. Is this good enough to possibly land my a job in the industry? If I left anything out or was not detail, please feel free to ask more questions. Edit: I do learn data structures and algorithms.

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• XNA Reach profile with VMWare - Vertex Buffers not working?

  - by Nektarios

  Running XNA app, using Reach profile, in VMWare Fusion host OS Mac OSX, VM is Windows XP SP 3 (my dual-boot OS). Running on MacBook Pro w/NVidia 320M graphics card When I am booted in to XP natively, my code works. The code is drawing cubes that are set up using vertex buffers When another friend runs this same code on Windows 7, it also works for him just fine When I am running my code in the VM, it doesn't work. I have billboarding sprites running in a shader program and this part displays fine. I get no crashing or errors, the geometry just doesn't appear. I tried Debug and Release. This is very basic operation so I'm thinking VMWare isn't the problem, but it's my code.... My init code: var vertexArray = verts.ToArray(); var indexArray = indices.ToArray(); indexBuffer = new IndexBuffer(GraphicsDevice, typeof(Int16), indexArray.Length, BufferUsage.WriteOnly); indexBuffer.SetData(indexArray); vertexBuffer = new VertexBuffer(GraphicsDevice, typeof(VertexPositionColor), vertexArray.Length, BufferUsage.WriteOnly); vertexBuffer.SetData(vertexArray); My Draw code: // problem isn't here, tried no cull GraphicsDevice.RasterizerState = RasterizerState.CullClockwise; GraphicsDevice.BlendState = BlendState.AlphaBlend; GraphicsDevice.DepthStencilState = new DepthStencilState() { DepthBufferEnable = true }; // Update View and Projection TileEffect.View = ((Game1)Game).Camera.View; TileEffect.Projection = ((Game1)Game).Camera.Projection; TileEffect.CurrentTechnique.Passes[0].Apply(); GraphicsDevice.SetVertexBuffer(vertexBuffer); GraphicsDevice.Indices = indexBuffer; GraphicsDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, indices.Count, 0, indices.Count / 3); For LoadContent: TileEffect = new BasicEffect(GraphicsDevice) { World = Matrix.Identity, View = ((Game1)Game).Camera.View, Projection = ((Game1)Game).Camera.Projection, VertexColorEnabled = true };

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• How can I convert a projection that's not part of spatial_ref_sys?

  - by Summer

  Hi, I'm importing shapefiles into a Postgres+PostGIS database. Here's my usual procedure: * Find an srid in the spatial_ref_sys table where srtext appears to match the shapefile's .prj file * Upload the data into a new table using the shp2pgsql utility, specifying the srid using the -s flag * Add the new table to my main geometry table, and on the way convert to an srid of 4269 (the Census standard projection) using ST_Transform Unfortunately, the spatial_ref_sys table doesn't include Mississippi state's standard projection. The contents of their .prj file is as follows, where I've bolded the parts I usually try to match: PROJCS["mstm",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",1300000.0],PARAMETER["Central_Meridian",-89.75],PARAMETER["Scale_Factor",0.9998335],PARAMETER["Latitude_Of_Origin",32.5],UNIT["Meter",1.0]] I eventually found the ogr2ogr utility, and especially with the "peace and joy" promises, I decided to give it a try. I tried this command: ogr2ogr -update -f "PostgreSQL" PG:"Connection details" "File name.shp" -t_srs EPSG:4269 -nln Table_Name I am now getting the error "Terminating translation prematurely after failed translation of layer" -- which seems to indicate that ogr2ogr is not going to be the savior I imagined in getting arbitrary .prj files neatly into the 4269 projection. Any ideas about what to do?

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• Rotate a feature Image in Open Layers - ReApply StyleMap to layer.

  - by Ozaki

  I have an open layers map. It adds and removes my "imageFeature" every 10secs or so. I have a JSON feed that gives me the rotation that I need, I have a request to get that rotation and set it as a variable of rotationv. Everything works but the fact when the image is recreated it does not update the rotation. My code is as follows: JSON request: var rotationv = (function () { rotationv = null; $.ajax({ 'async': false, 'global': true, 'url': urldefault, 'dataType': "json", 'success': function (data) { rotationv = data.rotation; } }); return rotationv })(); Creating image feature: imageFeature = new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(mylon, mylat), { rotation: rotationv } ); The image is set in the styling elsewhere. Why does this not rotate my image? Debugging with firebug I now notice that "rotationv" is updating as per it should be. But when the point is destroyed then added again it does not apply the new rotation... Add: I realised that the "image" is applied as per the layer. So I need to figure out how to re apply the stylemap to the layer so it will trigger the "update" on the page. //redefine layer 2 so it can be updated - test.js is just a 0.0 ref// var layer2 = new OpenLayers.Layer.GML("Layer 2", "test.js", { format: OpenLayers.Format.GeoJSON, styleMap: styleMap }); But even if I add the above into my function still no luck. Included map.addLayers([layer2]); into the function as well. Edit: Attaching stylemap: var styleMap = new OpenLayers.StyleMap({ "default": new OpenLayers.Style({ rotation: rotationv, labelXOffset: "0", labelYOffset: "-15", graphicZIndex: 1 }) });

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• Keymap issues with NX from Mac OS X Lion

  - by Andy

  I tried to answer the question from Mark: Keymap issues with NX from Mac OS X Lion to Ubuntu However, it is locked so I figured I would post a new question / answer. I have been trying to answer this for a few days now because I have no issues when connecting through NX Client (technically OpenNX) to FreeNX server from an iMac (with Lion), but if I try to connect with a Macbook Pro I get horrible keyboard binding issues. The fix that is working for me is to go into: ~/.nx/config/HOST.nxs and change: <option key="Current keyboard" value="false"/> <option key="Custom keyboard layout" value="empty"/> <option key="Grab keyboard" value="false"/> I have tried this on three NX Servers and all are fixed. Hope it helps or gets you closer. Always check in the ~/.nx/temp/ for the sshlog and see if --keyboard="empty/empty" instead of "pc105/en" because the Mac is really pc104. 9:05:35: startsession --session="HOST" --type="unix-gnome" --cache="8M" --images="32M" --link="adsl" --geometry="2556\ x1396" --screeninfo="2560x1440x32+render" --keyboard="empty/empty" --backingstore="1" --encryption="1" --composite="1" --\ shmem="1" --shpix="1" --streaming="1" --samba="0" --cups="0" --nodelay="1" --defer="0" --client="macosx" --media="0" --st\ rict="0" --aux="1"

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• GeoDjango: Exceptions for basic geographic queries

  - by omat

  I am having problems with geographic queries with GeoDjango running on SpatiaLite on my development environment. from django.contrib.gis.db import models class Test(models.Model): poly = models.PolygonField() point = models.PointField() geom = models.GeometryField() objects = models.GeoManager() Testing via shell: >>> from geotest.models import Test >>> from django.contrib.gis.geos import GEOSGeometry >>> >>> point = GEOSGeometry("POINT(0 0)") >>> point <Point object at 0x105743490> >>> poly = GEOSGeometry("POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))") >>> poly <Polygon object at 0x105743370> >>> With these definitions, lets try some basic geographic queries. First contains: >>> Test.objects.filter(point__within=poly) Assertion failed: (0), function appendGeometryTaggedText, file WKTWriter.cpp, line 228. Abort trap And the django shell dies. And with within: >>> Test.objects.filter(poly__contains=point) GEOS_ERROR: Geometry must be a Point or LineString Traceback (most recent call last): ... GEOSException: Error encountered checking Coordinate Sequence returned from GEOS C function "GEOSGeom_getCoordSeq_r". >>> Other combinations also cause a variety of exceptions. I must be missing something obvious as these are very basic. Any ideas?

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• Latex renewcommand not working properly

  - by Nazgulled

  Why is this not working: \documentclass[a4paper,10pt]{article} \usepackage{a4wide} \usepackage[T1]{fontenc} \usepackage[portuguese]{babel} \usepackage[latin1]{inputenc} \usepackage{indentfirst} \usepackage{listings} \usepackage{fancyhdr} \usepackage{url} \usepackage[compat2,a4paper,left=25mm,right=25mm,bottom=15mm,top=20mm]{geometry} \usepackage{color} \usepackage[colorlinks]{hyperref} \usepackage[pdftex]{graphicx} \renewcommand{\headrulewidth}{0.4pt} \renewcommand{\footrulewidth}{0.4pt} \pagestyle{fancy} \fancyhead[L]{\small Laboratórios de Informática III} \fancyhead[R]{\small Projecto 1 (Linguagem \textsf{C})} \lstset{ basicstyle=\ttfamily\footnotesize, showstringspaces=false, frame=single, tabsize=4, breaklines=true, } \definecolor{Section1}{rgb}{0.09,0.21,0.36} \definecolor{Section2}{rgb}{0.21,0.37,0.56} \definecolor{Section3}{rgb}{0.30,0.50,0.74} \hypersetup{ bookmarks=false, linkcolor=red, urlcolor=cyan, } \renewcommand{\section}[1]{\texorpdfstring{\color{green}#1}{#1}} \parskip=6pt \begin{document} \begin{titlepage} \begin{center} \includegraphics[width=5cm]{./logo.jpg}\\[1cm] \textsc{\LARGE Universidade do Minho}\\[1cm] \textsc{\large Licenciatura em Engenharia Informática\\Laboratórios de Informática III}\\[1.5cm] \rule{\linewidth}{0.5mm}\\[0.4cm] \huge{\textbf{\textsc{Relatório do Projecto 1 (Linguagem C)}}} \rule{\linewidth}{0.5mm} \vfill \begin{tabular}{c c} \includegraphics[width=3.5cm]{./nuno.jpg} & \includegraphics[width=3.5cm]{./ricardo.jpg} \\ \textsc{\large{Nuno Mendes (51161)}} & \textsc{\large{Ricardo Amaral (48404)}} \\ \end{tabular} \vfill \large{\today} \end{center} \end{titlepage} \tableofcontents \newpage \section{Introdução} Lorem ipsum... \newpage \appendix \section{\color{Section1}Diagrama das Estruturas de Dados} \begin{center} \includegraphics[width=16cm]{./Diagrama.pdf} \end{center} \end{document} ! LaTeX Error: Something's wrong--perhaps a missing \item. See the LaTeX manual or LaTeX Companion for explanation. Type H for immediate help. ... l.2 ...rline {1}\color {green}Teste}{3}{section.1} How can I make it work properly?

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• IBM Informix Spatial datablade LIneFromText function

  - by swatit

  Hi Everybody, I am using IBM-Informix for my school project as part of "Informix on-campus" ativity conduted by IBM. I am using spatial datablade to store spatial data. My spatial data table looks like, CREATE TABLE xmlTest (row_id integer NOT NULL,pre integer, post integer,parent integer,tagname varchar(40,1),point ST_POINT); Then I inserted the spatial data into the table. Now I am trying to select the 'Points' lying under given 'polygon', where the co-ordinates of the polygon are dynamic i.e co-ordinates will be decided in the 'select' query. My query is like SELECT v2.* FROM xmlTest v1,xmlTest v2 WHERE ST_Contains(ST_Polygon(ST_LineFromText('linestring (0 0, 22000 0,22000 22000,0 22000,0 0)',5)),ST_Point(v1.pre,v1.post,5)) AND v1.tagname like 'n1' AND ST_Contains(ST_Polygon(ST_LineFromText('linestring (0 0,v1.pre 0,v1.pre v1.post,0 v1.post,0 0 )',5)),ST_Point(v2.pre,v2.post,5)) AND v2.tagname like 'n2' however it is giving me error as "(USE31) - Too few points for geometry type in ST_LineFromText.", in the second linefromtext function. I checked the number of parameters for linestring function, but could not find the source of error. I think,linestring function's parameters should be fixed values and not the variable like in this query. Is it right? Then what is the alternate way, where I can specify my polygon co-ordinates dynamically? or is there any mistake in my query? I hope my question is clear. I appreciate your help!

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• Calling/selecting variables (float valued) with user input in Python

  - by Jonathan Straus

  I've been working on a computational physics project (plotting related rates of chemical reactants with respect to eachother to show oscillatory behavior) with a fair amount of success. However, one of my simulations involves more than two active oscillating agents (five, in fact) which would obviously be unsuitable for any single visual plot... My scheme was hence to have the user select which two reactants they wanted plotted on the x-axis and y-axis respectively. I tried (foolishly) to convert string input values into the respective variable names, but I guess I need a radically different approach if any exist? If it helps clarify any, here is part of my code: def coupledBrusselator(A, B, t_trial,display_x,display_y): t = 0 t_step = .01 X = 0 Y = 0 E = 0 U = 0 V = 0 dX = (A) - (B+1)*(X) + (X**2)*(Y) dY = (B)*(X) - (X**2)*(Y) dE = -(E)*(U) - (X) dU = (U**2)*(V) -(E+1)*(U) - (B)*(X) dV = (E)*(U) - (U**2)*(V) array_t = [0] array_X = [0] array_Y = [0] array_U = [0] array_V = [0] while t <= t_trial: X_1 = X + (dX)*(t_step/2) Y_1 = Y + (dY)*(t_step/2) E_1 = E + (dE)*(t_step/2) U_1 = U + (dU)*(t_step/2) V_1 = V + (dV)*(t_step/2) dX_1 = (A) - (B+1)*(X_1) + (X_1**2)*(Y_1) dY_1 = (B)*(X_1) - (X_1**2)*(Y_1) dE_1 = -(E_1)*(U_1) - (X_1) dU_1 = (U_1**2)*(V_1) -(E_1+1)*(U_1) - (B)*(X_1) dV_1 = (E_1)*(U_1) - (U_1**2)*(V_1) X_2 = X + (dX_1)*(t_step/2) Y_2 = Y + (dY_1)*(t_step/2) E_2 = E + (dE_1)*(t_step/2) U_2 = U + (dU_1)*(t_step/2) V_2 = V + (dV_1)*(t_step/2) dX_2 = (A) - (B+1)*(X_2) + (X_2**2)*(Y_2) dY_2 = (B)*(X_2) - (X_2**2)*(Y_2) dE_2 = -(E_2)*(U_2) - (X_2) dU_2 = (U_2**2)*(V_2) -(E_2+1)*(U_2) - (B)*(X_2) dV_2 = (E_2)*(U_2) - (U_2**2)*(V_2) X_3 = X + (dX_2)*(t_step) Y_3 = Y + (dY_2)*(t_step) E_3 = E + (dE_2)*(t_step) U_3 = U + (dU_2)*(t_step) V_3 = V + (dV_2)*(t_step) dX_3 = (A) - (B+1)*(X_3) + (X_3**2)*(Y_3) dY_3 = (B)*(X_3) - (X_3**2)*(Y_3) dE_3 = -(E_3)*(U_3) - (X_3) dU_3 = (U_3**2)*(V_3) -(E_3+1)*(U_3) - (B)*(X_3) dV_3 = (E_3)*(U_3) - (U_3**2)*(V_3) X = X + ((dX + 2*dX_1 + 2*dX_2 + dX_3)/6) * t_step Y = Y + ((dX + 2*dY_1 + 2*dY_2 + dY_3)/6) * t_step E = E + ((dE + 2*dE_1 + 2*dE_2 + dE_3)/6) * t_step U = U + ((dU + 2*dU_1 + 2*dY_2 + dE_3)/6) * t_step V = V + ((dV + 2*dV_1 + 2*dV_2 + dE_3)/6) * t_step dX = (A) - (B+1)*(X) + (X**2)*(Y) dY = (B)*(X) - (X**2)*(Y) t_step = .01 / (1 + dX**2 + dY**2) ** .5 t = t + t_step array_X.append(X) array_Y.append(Y) array_E.append(E) array_U.append(U) array_V.append(V) array_t.append(t) where previously display_x = raw_input("Choose catalyst you wish to analyze in the phase/field diagrams (X, Y, E, U, or V) ") display_y = raw_input("Choose one other catalyst from list you wish to include in phase/field diagrams ") coupledBrusselator(A, B, t_trial, display_x, display_y) Thanks!

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• Rotate a feature Image in Open Layers - Javascript variable from JSON.

  - by Ozaki

  I have an open layers map. It adds and removes my "imageFeature" every 10secs or so. I have a JSON feed that gives me the rotation that I need, I have a request to get that rotation and set it as a variable of rotationv. Everything works but the fact when the image is recreated it does not update the rotation. My code is as follows: JSON request: var rotationv = (function () { rotationv = null; $.ajax({ 'async': false, 'global': true, 'url': urldefault, 'dataType': "json", 'success': function (data) { rotationv = data.rotation; } }); return rotationv })(); Creating image feature: imageFeature = new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(mylon, mylat), { rotation: rotationv } ); The image is set in the styling elsewhere. Why does this not rotate my image? Debugging with firebug I now notice that "rotationv" is updating as per it should be. But when the point is destroyed then added again it does not apply the new rotation... Add: I realised that the "image" is applied as per the layer. So I need to figure out how to re apply the stylemap to the layer so it will trigger the "update" on the page. //redefine layer 2 so it can be updated// //test.js is just a 0.0 testref// var layer2 = new OpenLayers.Layer.GML("Layer 2", "test.js", { format: OpenLayers.Format.GeoJSON, styleMap: styleMap }); But even if I add the above into my function still no luck. Included map.addLayers([layer2]); into the function as well.

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• Deserialize complex JSON (VB.NET)

  - by Ssstefan

  I'm trying to deserialize json returned by some directions API similar to Google Maps API. My JSON is as follows (I'm using VB.NET 2008): jsontext = { "version":0.3, "status":0, "route_summary": { "total_distance":300, "total_time":14, "start_point":"43", "end_point":"42" }, "route_geometry":[[51.025421,18.647631],[51.026131,18.6471],[51.027802,18.645639]], "route_instructions": [["Head northwest on 43",88,0,4,"88 m","NW",334.8],["Continue on 42",212,1,10,"0.2 km","NW",331.1,"C",356.3]] } So far I came up with the following code: Dim js As New System.Web.Script.Serialization.JavaScriptSerializer Dim lstTextAreas As Output_CloudMade() = js.Deserialize(Of Output_CloudMade())(jsontext) I'm not sure how to define complex class, i.e. Output_CloudMade. I'm trying something like: Public Class RouteSummary Private mTotalDist As Long Private mTotalTime As Long Private mStartPoint As String Private mEndPoint As String Public Property TotalDist() As Long Get Return mTotalDist End Get Set(ByVal value As Long) mTotalDist = value End Set End Property Public Property TotalTime() As Long Get Return mTotalTime End Get Set(ByVal value As Long) mTotalTime = value End Set End Property Public Property StartPoint() As String Get Return mStartPoint End Get Set(ByVal value As String) mStartPoint = value End Set End Property Public Property EndPoint() As String Get Return mEndPoint End Get Set(ByVal value As String) mEndPoint = value End Set End Property End Class Public Class Output_CloudMade Private mVersion As Double Private mStatus As Long Private mRSummary As RouteSummary 'Private mRGeometry As RouteGeometry 'Private mRInstructions As RouteInstructions Public Property Version() As Double Get Return mVersion End Get Set(ByVal value As Double) mVersion = value End Set End Property Public Property Status() As Long Get Return mStatus End Get Set(ByVal value As Long) mStatus = value End Set End Property Public Property Summary() As RouteSummary Get Return mRSummary End Get Set(ByVal value As RouteSummary) mRSummary = value End Set End Property 'Public Property Geometry() As String ' Get ' End Get ' Set(ByVal value As String) ' End Set 'End Property 'Public Property Instructions() As String ' Get ' End Get ' Set(ByVal value As String) ' End Set 'End Property End Class but it does not work. The problem is with complex properties, like route_summary. It is filled with "nothing". Other properties, like "status" or "version" are filled properly. Any ideas, how to define class for the above JSON? Can you share some working code for deserializing JSON in VB.NET? Thanks,

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• Oracle output: cursor, file, or very long string?

  - by Klay

  First, the setup: I have a table in an Oracle10g database with spatial columns. I need to be able to pass in a spatial reference so that I can reproject the geometry into an arbitrary coordinate system. Ultimately, I need to compress the results of this projection to a zip file and make it available for download through a Silverlight project. I would really appreciate ideas as to the best way to accomplish this. In the examples below, the SRID is the Spatial reference ID integer used to convert the geometric points into a new coordinate system. In particular, I can see a couple of possibilities. There are many more, but this is an idea of how I'm thinking: a) Pass SRID to a dynamic view -- perform projection, output a cursor -- send cursor to UTL_COMPRESS -- write output to a file (somehow) -- send URL to Silverlight app b) Use SRID to call Oracle function from Silverlight app -- perform projection, output a string -- build strings into a file -- compress file using SharpZipLib library in .NET -- send bytestream back to Silverlight app I've done the first two steps of b), and the conversion of 100 points took about 7 seconds, which is unacceptably slow. I'm hoping it would be faster doing the processing totally in Oracle. If anyone can see potential problems with either way of doing this, or can suggest a better way, it would be very helpful. Thanks!

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• How to create a semi transparent window in WPF that allows mouse events to pass through

  - by RMK

  I am trying to create an effect similar to the Lights out /lights dim feature in Adobe Lightroom (http://www.youtube.com/watch?v=87hNd3vaENE) except in WPF. What I tried was to create another window over-top of my existing window, make it transparent and put a semi transparent Path geometry on it. But I want mouse events to be able to pass through this semi transparent window (on to windows below). This is a simplified version of what I have: <Window x:Class="LightsOut.MaskWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" AllowsTransparency="True" WindowStyle="None" ShowInTaskbar="False" Topmost="True" Background="Transparent"> <Grid> <Button HorizontalAlignment="Left" Height="20" Width="60">click</Button> <Path IsHitTestVisible="False" Stroke="Black" Fill="Black" Opacity="0.3"> <Path.Data> <RectangleGeometry Rect="0,0,1000,1000 "/> </Path.Data> </Path> </Grid> The window is fully transparent, so on places where the Path doesn't cover, mouse events pass right through. So far so good. The IsHitTestvisible is set to false on the path object. So mouse events will pass through it to other controls on the same form (ie you can click on the Button, because it is on the same form). But mouse events wont pass through the Path object onto windows that are below it. Any ideas? Or better ways to solve this problem? Thanks.

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• Geolocation and jQuery - Can't post results using ajax

  - by etombaugh

  I'm currently working on a project to make a location-aware site. In essence, the user comes to the page, and their location is found using the HTML5 method and then using jQuery, the location is posted to a page which saves the location/address to a codeigniter session, but if they want to update their location, or change to a different location(IE they want to use their work address as the location instead of their present address), theres a jQuery colorbox that displays and lets them type in a custom address. Everything works flawlessly to get the initial location, but when I try and get the updated location saved, I receive the error "Uncaught TypeError: Object [object DOMWindow] has no method 'lat'" which then Google Chrome references as being an error not in jQuery, but in the file for Google Maps API. Any suggestions? jQuery('.inputsubmit').click(function() { //Takes values from user submitted fields and parses them into an address string var street = jQuery('.inputaddress').val(); var city = jQuery('.inputcity').val(); var state = jQuery('.inputstate').val(); var address = street +" "+ city +", " +state; geocoder = new google.maps.Geocoder(); var geocoderresult= geocoder.geocode({'address': address}, function(results, status) { if (status == google.maps.GeocoderStatus.OK) { var newlocation = results[0].geometry.location; //Posts coordinates and address string to a CodeIgniter function to update users session information jQuery.post("somepage", {location: newlocation, address: address},function(data) { alert("Data Loaded: " + data); }); } else { alert("Geocoder failed due to: " + status); } }); }); I've tried everything I can think of to get the post to work. All of the code works up till the point, and I've commented out the post line and everything works correctly. This is one of our main website's features, to provide instant and quick results based off of location. Thanks!

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• Need guidelines for optimizing WebGL performance by minimizing shader changes

  - by brainjam

  I'm trying to get an idea of the practicality of WebGL for rendering large architectural interior scenes, consisting of 100K's of triangles. These triangles are distributed over many objects, and there are many materials in the scene. On the other hand, there are no moving parts. And the materials tend to be fairly simple, mostly based on texture maps. There is a lot of texture map sharing .. for example all the chairs in scene will share a common map. There is also some multitexturing - up to three textures overlaid in a material. I've been doing a little experimentation and reading, and gather that frequently switching materials during a rendering pass will slow things down. For example, a scene with 200K triangles will have significant performance differences, depending on whether there are 10 or 1000 objects, assuming that each time an object is displayed a new material is set up. So it seems that if performance is important the scene should be sorted by materials so as to minimize material switching. What I'm looking for is guidelines on how to think of the overhead of various state changes, and where do I get the biggest bang for the buck. For example, what are the relative performance costs of, say, gl.useProgram(), gl.uniformMatrix4fv(), gl.drawElements() should I try to write ubershaders to minimize shader switching? should I try to aggregate geometry to minimize the number of gl.drawElements() calls I realize that mileage may vary depending on browser, OS, and graphics hardware. And I'm also not looking for heroic measures. Just some guidelines from people who have already had some experience in making scenes fast. I'll add that while I've had some experience with fixed-pipeline OpenGL programming in the past, I'm rather new to the WebGL/OpenGL ES 2.0 way of doing things.

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• Is there a way to automaticly call all versions of an inherited method?

  - by Eric

  I'm writing a plug-in for a 3D modeling program. I have a custom class that wraps instances of elements in the 3D model, and in turn derives it's properties from the element it wraps. When the element in the model changes I want my class(es) to update their properties based on the new geometry. In the simplified example below. I have classes AbsCurveBasd, Extrusion, and Shell which are all derived from one another. Each of these classes implement a RefreshFromBaseShape() method which updates specific properties based on the current baseShape the class is wrapping. I can call base.RefreshFromBaseShape() in each implementation of RefreshFromBaseShape() to ensure that all the properties are updated. But I'm wondering if there is a better way where I don't have to remember to do this in every implementation of RefershFromBaseShape()? For example because AbsCurveBased does not have a parameterless constructor the code wont even compile unless the constructors call the base class constructors. public abstract class AbsCurveBased { internal Curve baseShape; double Area{get;set;} public AbsCurveBased(Curve baseShape) { this.baseShape = baseShape; RefreshFromBaseShape(); } public virtual void RefreshFromBaseShape() { //sets the Area property from the baseShape } } public class Extrusion : AbsCurveBased { double Volume{get;set;} double Height{get;set;} public Extrusion(Curve baseShape):base(baseShape) { this.baseShape = baseShape; RefreshFromBaseShape(); } public override void RefreshFromBaseShape() { base.RefreshFromBaseShape(); //sets the Volume property based on the area and the height } } public class Shell : Extrusion { double ShellVolume{get;set;} double ShellThickness{get;set;} public Shell(Curve baseShape): base(baseShape) { this.baseShape = baseShape; RefreshFromBaseShape(); } public void RefreshFromBaseShape() { base.RefreshFromBaseShape(); //sets this Shell Volume from the Extrusion properties and ShellThickness property } }

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• NHibernate complex order query

  - by manu08

  Here's my simplified domain public class Notification { public Guid ID { get; set; } public string Name { get; set; } public IEnumerable<Location> Locations { get; set; } } public class Location { public Guid Id { get; set; } public string Name { get; set; } public decimal Longitude { get; set; } public decimal Latitude { get; set; } } Notifications and Locations have a many-to-many relationship (defined in table LocationsOnNotification). What I'd like to do is query for the nearest 10 Notifications from a given longitude and latitude. I've been trying to use ICriteria, but I'm not sure how to specify the ordering correctly: return Session.CreateCriteria<Notification>() .SetFirstResult(firstIndex) .SetMaxResults(maxResults) .AddOrder(Order.Asc( WHAT GOES HERE! )) .List<Notification>(); What I've been thinking of so far is adding a formula property to the Location mapping; something like this: <property name='Distance' formula='lots of geometry'/> But I'm not sure if that can take in parameters (since I'd need to pass in the user's location to calculate the distance), plus I'm not sure how to specify it in the Order.Asc clause given that it's a property on a many-to-many association class. Any ideas? Or perhaps I should take a different approach altogether. Thanks in advance!

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• Extending the .NET type system so the compiler enforces semantic meaning of primitive values in cert

  - by Drew Noakes

  I'm working with geometry a bit at the moment and am converting a lot between degrees and radians. Unfortunately, both of these are represented by double, so there's compile time warning/error if I try to pass a value in degrees where radians are expected. I believe F# has a compile-time solution for this (called units of measure.) I'd like to do something similar in C#. As another example, imagine a SQL library that accepts various query parameters as strings. It'd be good to have a way of enforcing that only clean strings were allowed to be passed in at runtime, and the only way to get a clean string was to pass through some SQL injection attack preventing logic. The obvious solution is to wrap the double/string/whatever in a new type to give it the type information the compiler needs. I'm curious if anyone has an alternative solution. If you do think wrapping is the only/best way, then please go into some of the downsides of the pattern (and any upsides I haven't mentioned too.) I'm especially concerned about the performance of abstracted primitive numeric types on my calculations at runtime.

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• Qt/PyQt dialog with toggable fullscreen mode - problem on Windows

  - by Guard

  I have a dialog created in PyQt. It's purpose and functionality don't matter. The init is: class MyDialog(QWidget, ui_module.Ui_Dialog): def __init__(self, parent=None): super(MyDialog, self).__init__(parent) self.setupUi(self) self.installEventFilter(self) self.setWindowFlags(Qt.Dialog | Qt.WindowTitleHint) self.showMaximized() Then I have event filtering method: def eventFilter(self, obj, event): if event.type() == QEvent.KeyPress: key = event.key() if key == Qt.Key_F11: if self.isFullScreen(): self.setWindowFlags(self._flags) if self._state == 'm': self.showMaximized() else: self.showNormal() self.setGeometry(self._geometry) else: self._state = 'm' if self.isMaximized() else 'n' self._flags = self.windowFlags() self._geometry = self.geometry() self.setWindowFlags(Qt.Tool | Qt.FramelessWindowHint) self.showFullScreen() return True elif key == Qt.Key_Escape: self.close() return QWidget.eventFilter(self, obj, event) As can be seen, Esc is used for dialog hiding, and F11 is used for toggling full-screen. In addition, if the user changed the dialog mode from the initial maximized to normal and possibly moved the dialog, it's state and position are restored after exiting the full-screen. Finally, the dialog is created on the MainWindow action triggered: d = MyDialog(self) d.show() It works fine on Linux (Ubuntu Lucid), but quite strange on Windows 7: if I go to the full-screen from the maximized mode, I can't exit full-screen (on F11 dialog disappears and appears in full-screen mode again. If I change the dialog's mode to Normal (by double-clicking its title), then go to full-screen and then return back, the dialog is shown in the normal mode, in the correct position, but without the title line. Most probably the reason for both cases is the same - the setWindowFlags doesn't work. But why? Is it also possible that it is the bug in the recent PyQt version? On Ubuntu I have 4.6.x from apt, and on Windows - the latest installer from the riverbank site.

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