Monday, September 23, 2013
Homepage
Restored and updated my old research homepage. http://perttu.info is now redirecting there. Nothing special, mainly lists of publications and projects.
Wednesday, June 26, 2013
Game programming tips
Starting a link collection here...
Remember to avoid transform.position=xxx... in Unity. Here's why:
Friday, May 10, 2013
Trampolines as a business
Related to our Kinect trampoline and circus games, I just checked that Googling "trampoline park" gives 628000 results. Trampoline centers/parks seem to be a growing branch of the family entertainment center business, as discussed, e.g., in this article about the Sky Zone franchise, which had 15 centers in the U.S. and planned to more than double that when the article was written in 2012.
Here's two pretty compelling videos, the first one from House of Air from the U.S. and the second one from Bounz, one of the few European ones.
Despite the thrill, it remains unclear whether trampoline parks are craze that will fade like the soft-contained-play (SCP) and inflatable centers did, as explained in this article. According to the author, trampoline centers are similar to SCP and inflatable centers in that they too haven't proven their business model for long-term viability, and they are at the same time more dangerous. However, I think that while trampolines may be more dangerous than bouncing castles, they also present much more potential for long term excitement, as the increased air time and softer landings make it possible to learn a wider variety of skills and tricks. For example, it's not very comfortable to land on one's back or belly on an inflatable bouncing surface, whereas it's quite easy on a trampoline and one can also do many interesting variations, such as turntabling:
Monday, April 8, 2013
Action Games Workshop info (Aalto course code 25447)
Since we are using a generic course code and I can't edit the contents and learning outcomes in Noppa, I'm posting the material here.
Click "register" at the bottom of the page. Note that the Oodi page is a generic one, since the course doesn't yet have its own course code and page. Note also that you can find the updated course description by clicking the "Workshop I" teaching event at the bottom of the page, but Oodi doesn't let you register on that page - I would have linked directly to it otherwise.
The number of participants is limited to 14, not including me and Miikka of course.
Remember to bring indoor sports clothes and shoes. Climbing shoes will be provided by Boulderkeskus.
Contents
Many games are simplifications and abstractions of reality. The designer's job is to abstract away irrelevant and/or cumbersome details, and choosing what to focus on is not trivial. Background research helps, but in addition to gathering mediated experiences in the form of text, images, and video, it's useful to experience things in person.
On this course, we will experience various sports and their digital representations to identify yet uncharted possibilities for action games. The course consists of physical activities mixed with lectures, gaming sessions, and interaction sketching exercises. In spring 2013, the course is organized for the first time as a workshop including parkour, trampolining, archery, swordfighting, contemporary dance, and bouldering (climbing) with help of professional instructors.
An additional goal of the course is to share the latest insights from Aalto’s games and motion related research.
Learning outcomes
Gain insights and ideas for gameplay design from the points of view of, e.g., embodied experiences, biomechanics, motor learning and performance, physics simulation, and virtual cinematography. Understand the variety of embodied experiences, ranging from passive media to console games to experimental mixed reality games.
How to register
You can sign up in Oodi: https://oodi.aalto.fi/a/opintjakstied.jsp?Kieli=6&Tunniste=25447&html=1.Click "register" at the bottom of the page. Note that the Oodi page is a generic one, since the course doesn't yet have its own course code and page. Note also that you can find the updated course description by clicking the "Workshop I" teaching event at the bottom of the page, but Oodi doesn't let you register on that page - I would have linked directly to it otherwise.
The number of participants is limited to 14, not including me and Miikka of course.
Prerequisites
Preliminary exercise: for the first gathering, prepare a few minutes presentation about a physical activity, such as your favorite sport. Illustrate your presentation with image(s) or video. Answer these questions: What's interesting, fun and motivating about it? How do you feel when practicing/competing? Has it affected the way you experience the world? How? Is there a digital version of it or a digital dimension to it? If so, how does the digital user experience differ from the real thing or what does the digital dimension contribute?Schedule
The course is organized during 22-26.4.2013. We'll start each day with a physical activity.
Monday 22nd 9-11am: Trampolining and parkour at Taitoliikuntakeskus. How to get there: http://www.taitoliikuntakeskus.fi/?q=node/15
Tuesday 23rd 9-12am: Archery at Archery Club Wilhelm Tell. Place: Katri Valan puiston väestönsuoja: http://bit.ly/16Ivuva
Wednesday 24th 9:30-12:30: Medieval swordmanship at The School of European Swordmanship. Address Luiskatie 8, Helsinki (e.g, bus 77)
Thursday 25th 9:30-11:30: Contemporary dance at Helsingin Tanssiopisto. Address: Kaikukatu 4, http://bit.ly/Zi5LoQ
Friday 26th 10-12am: Bouldering (climbing) at Boulderkeskus, Konala. Address: Ruosilantie 1, http://bit.ly/16IknEq
Remember to bring indoor sports clothes and shoes. Climbing shoes will be provided by Boulderkeskus.
In addition to the activities, we'll have lectures and exercises each afternoon from 13:00-16:00 at the Media Lab games classroom. I'm currently preparing the materials, and so far the tentative themes for the afternoons are controls & virtual cinematography, character animation & biomechanics, physics based gameplay, story & emotion, and motion games & games for learning.
Monday, January 28, 2013
Visualizing Fitness Function Landscapes
I'm currently preparing a project about game animation tools and technology. The project is exploring and leveraging technologies like physics simulation, optimization and machine learning. If you are interested, the recent review by Geijtenbeek and Pronost is a good starting point.
Related to the optimization of the control parameters of physics simulation, I'm trying to form an intuition about the properties of the related fitness function landscapes. It's impossible to accurately visualize the landscapes of high-dimensional biped motor control and planning problems, but here's a simple 2d physics example: throwing a ball in 2d with the angle and speed as the optimized variables, and allowing damped rebounds from the ground so that the ball trajectory is not just a simple parabola. This isn't exactly rocket science, but I wrote the code to as an exercise in interactive visualization in Matlab, which I stopped using while working outside Aalto.
It was my first time I tried to do implement the "up and down the ladder of abstraction", that is, letting the user explore a summary view (the fitness landscape) to browse concrete examples (the ball trajectories). There was some non-intuitive searching for the right places to put the getCursorInfo(), pause() and subplot() commands to prevent the display from freezing - hope this helps if anyone wants to do the same. I also tried to implement the UI using Matlab's linked data, but couldn't get the display refreshed.
Edit 29.1.2013: I was asked why there's peaks where there should be a continuous ridge. It's apparently because of the large timestep that causes a simulation error that varies as a function of how the floor contacts align with the timestep grid. It also depends on how the contact handling is implemented. The Matlab code below uses a smaller timestep and produces a more continuous ridge.
Here's the Matlab code:
minVel=1;
maxVel=5.0;
minAngle=-0.5*pi;
maxAngle=0.5*pi;
timeStep=0.02;
nSteps=100;
startPos=[0,1.5];
velSteps=64;
angleSteps=64;
E=zeros(velSteps,angleSteps);
target=[2, 0.5];
curve=zeros(nSteps,2);
curves=zeros(nSteps,2,velSteps,angleSteps);
%step over all ball launch speed and angle combinations
for velStep=0:velSteps,
speed=minVel+(maxVel-minVel)*velStep/velSteps;
for angleStep=0:angleSteps,
angle=minAngle+(maxAngle-minAngle)*angleStep/angleSteps;
pos=startPos;
vel=[speed*cos(angle), speed*sin(angle)];
closestDist=10000;
closest=[0; 0];
closestTime=0;
%simulate the ball trajectory for this launch velocity
for n=1:nSteps,
%save this trajectory point
curve(n,:)=pos;
%update closest to target
dist=norm(pos-target,2);
if (dist<closestDist)
closestDist=dist;
closest=pos;
closestTime=n*timeStep;
end
%physics update
pos=pos+vel*timeStep;
vel(2)=vel(2)-9.81*timeStep;
%bounce from floor
if (pos(2)<0 && vel(2)<0)
timeInsideGround=pos(2)/vel(2);
vel(2)=-0.7*vel(2);
timeAfterBounce=max(0,timeStep-timeInsideGround);
pos(2)=timeAfterBounce*vel(2);
end
end
%store the whole trajectory
curves(:,:,velStep+1,angleStep+1)=curve;
%update fitness
distanceThreshold=0.1;
fitness=0.5+0.5*tanh(-(closestDist-distanceThreshold)/0.05);
%soft threshold for hitting time
timeThreshold=1;
fitness=fitness*(0.5+0.5*tanh(-(closestTime-timeThreshold)/0.05));
%store fitness function value for these params
E(velStep+1,angleStep+1)=fitness;
end
end
%plot the fitness surface
subplot(1,2,1);
surf(E);
%get the handle for querying data cursor info about the fitness
h=gcf;
dcm_obj = datacursormode(h)
%plot a trajectory of the ball
subplot(1,2,2);
curve=curves(:,:,1,1);
plot(curve(:,1),curve(:,2));
%in a loop, keep plotting the ball trajectories
pause on;
while 1
info_struct = getCursorInfo(dcm_obj);
if size(info_struct)~=0
curve=curves(:,:,floor(info_struct.Position(2)),floor(info_struct.Position(1)));
subplot(1,2,2);
plot(curve(:,1),curve(:,2));
axis([0 4.5 0 3])
hold on;
plot(target(1),target(2),'c+:')
hold off;
end
%have to pause to let the display refresh
pause(0.01);
end
Related to the optimization of the control parameters of physics simulation, I'm trying to form an intuition about the properties of the related fitness function landscapes. It's impossible to accurately visualize the landscapes of high-dimensional biped motor control and planning problems, but here's a simple 2d physics example: throwing a ball in 2d with the angle and speed as the optimized variables, and allowing damped rebounds from the ground so that the ball trajectory is not just a simple parabola. This isn't exactly rocket science, but I wrote the code to as an exercise in interactive visualization in Matlab, which I stopped using while working outside Aalto.
It was my first time I tried to do implement the "up and down the ladder of abstraction", that is, letting the user explore a summary view (the fitness landscape) to browse concrete examples (the ball trajectories). There was some non-intuitive searching for the right places to put the getCursorInfo(), pause() and subplot() commands to prevent the display from freezing - hope this helps if anyone wants to do the same. I also tried to implement the UI using Matlab's linked data, but couldn't get the display refreshed.
Edit 29.1.2013: I was asked why there's peaks where there should be a continuous ridge. It's apparently because of the large timestep that causes a simulation error that varies as a function of how the floor contacts align with the timestep grid. It also depends on how the contact handling is implemented. The Matlab code below uses a smaller timestep and produces a more continuous ridge.
Here's the Matlab code:
minVel=1;
maxVel=5.0;
minAngle=-0.5*pi;
maxAngle=0.5*pi;
timeStep=0.02;
nSteps=100;
startPos=[0,1.5];
velSteps=64;
angleSteps=64;
E=zeros(velSteps,angleSteps);
target=[2, 0.5];
curve=zeros(nSteps,2);
curves=zeros(nSteps,2,velSteps,angleSteps);
%step over all ball launch speed and angle combinations
for velStep=0:velSteps,
speed=minVel+(maxVel-minVel)*velStep/velSteps;
for angleStep=0:angleSteps,
angle=minAngle+(maxAngle-minAngle)*angleStep/angleSteps;
pos=startPos;
vel=[speed*cos(angle), speed*sin(angle)];
closestDist=10000;
closest=[0; 0];
closestTime=0;
%simulate the ball trajectory for this launch velocity
for n=1:nSteps,
%save this trajectory point
curve(n,:)=pos;
%update closest to target
dist=norm(pos-target,2);
if (dist<closestDist)
closestDist=dist;
closest=pos;
closestTime=n*timeStep;
end
%physics update
pos=pos+vel*timeStep;
vel(2)=vel(2)-9.81*timeStep;
%bounce from floor
if (pos(2)<0 && vel(2)<0)
timeInsideGround=pos(2)/vel(2);
vel(2)=-0.7*vel(2);
timeAfterBounce=max(0,timeStep-timeInsideGround);
pos(2)=timeAfterBounce*vel(2);
end
end
%store the whole trajectory
curves(:,:,velStep+1,angleStep+1)=curve;
%update fitness
distanceThreshold=0.1;
fitness=0.5+0.5*tanh(-(closestDist-distanceThreshold)/0.05);
%soft threshold for hitting time
timeThreshold=1;
fitness=fitness*(0.5+0.5*tanh(-(closestTime-timeThreshold)/0.05));
%store fitness function value for these params
E(velStep+1,angleStep+1)=fitness;
end
end
%plot the fitness surface
subplot(1,2,1);
surf(E);
%get the handle for querying data cursor info about the fitness
h=gcf;
dcm_obj = datacursormode(h)
%plot a trajectory of the ball
subplot(1,2,2);
curve=curves(:,:,1,1);
plot(curve(:,1),curve(:,2));
%in a loop, keep plotting the ball trajectories
pause on;
while 1
info_struct = getCursorInfo(dcm_obj);
if size(info_struct)~=0
curve=curves(:,:,floor(info_struct.Position(2)),floor(info_struct.Position(1)));
subplot(1,2,2);
plot(curve(:,1),curve(:,2));
axis([0 4.5 0 3])
hold on;
plot(target(1),target(2),'c+:')
hold off;
end
%have to pause to let the display refresh
pause(0.01);
end
Thursday, January 24, 2013
Game marketing resources
To help our students in promoting their games, I did about an hour's worth of searching, both using Google and digging up old stuff from my brain. Dumping the results here for future reference, roughly in the order of importance.
About creating press releases etc.
http://gdcvault.com/play/1014971/Indie-s-Got-PR-Talent
http://arstechnica.com/gaming/2011/12/how-to-market-your-indie-games-ben-kucheras-lecture-at-run-jump-dev//
http://gamasutra.com/view/news/167706/Ask_Gamasutra_How_to_annoy_a_games_journalist_with_a_press_release.php#.UQE7syfZZ8E
http://www.gamestyleguide.com/VideoGameStyleGuideeBook.pdf (Talk to the journalists using their own language)
http://dopresskit.com/ Presskit making tool. Note: I haven't tried it personally.
How to make good trailers
http://indiegames.com/2012/04/ask_indiegames_what_makes_an_e.html
http://blog.kertgartner.com/2012/03/making-entertaining-and-engaging-video-game-trailers/
http://www.indiegamegirl.com/how-to-make-a-video-game-trailer-kick-ass/
http://www.ign.com/articles/2012/05/01/five-sure-signs-of-an-awesome-game-trailer
http://www.reddit.com/r/Games/comments/16g1x7/that_great_cyberpunk_2077_teaser_got_me_thinking/
http://www.reddit.com/r/Games/comments/zd84h/what_have_been_the_best_game_trailers_you_have/
http://gametheoryonline.com/2011/05/06/video-game-marketing-creating-game-tr
Stats to inform your decisions: http://engage.tmgcustommedia.com/2011/04/101-online-video-stats-to-make-your-eyes-glaze-over/
Tuesday, January 22, 2013
A note on backstory and child's play
The backstory is perhaps the most common literary device used in games. Understanding its importance is easy if one has followed the mobile game space, where many hugely successful games have a story-based motivation that can be expressed in a single sentence, such as "The frog wants the candy" or "The birds are angry because the pigs stole their eggs".
What wasn't obvious to me until I became a dad was that the backstory works perfectly similarly in child's play. It's been amazing to see firsthand how big a difference it can make in motivating play. For example, when its -10 centigrades outside, a common temperature this winter, my son hates to go out because putting on all the layers of clothes is such a tedious process. However, he immediately jumps up from the sofa if I throw in a backstory.
Me: "Let's go outside sled riding"
Son: "I don't want to go outside. It's boring. I don't want to wear the overalls."
Me: "But we can pretend to be Angry Birds. You can be the laser bird and have a snowball as a laser."
Son: "Cool! Let's go right away! Come on, dad!"
Malone's and Lepper's taxonomy of intrinsic motivation comprises four main motivating factors: challenge, curiosity, control, fantasy. Having a backstory provides a fantasy setting, and also provides material for curiosity, because one can explore how far the fantasy can be extended by using the play space, e.g., the snowballs. It can also inspire the child to come up with challenges. Many times, if I'm too tired to play cops and robbers, my son is happy to do all the running around by himself while I just sit on the couch and press imaginary buttons to control him on an imaginary iPad.
"Now I'm in level 13, and this is really hard. There's dynamite and I must not fall into the water (floor). Now press the button that makes me run to the door."
"You are the laser piggy. I must not hit the lasers."
Pretty contradictory considering that digital games are supposed to promote a sedentary lifestyle. Of course my son would never let go of the iPad voluntarily, but allowing him a controlled amount of daily gameplay seems to only boost his physical play by providing new backstories, similar to the books we read.
What wasn't obvious to me until I became a dad was that the backstory works perfectly similarly in child's play. It's been amazing to see firsthand how big a difference it can make in motivating play. For example, when its -10 centigrades outside, a common temperature this winter, my son hates to go out because putting on all the layers of clothes is such a tedious process. However, he immediately jumps up from the sofa if I throw in a backstory.
Me: "Let's go outside sled riding"
Son: "I don't want to go outside. It's boring. I don't want to wear the overalls."
Me: "But we can pretend to be Angry Birds. You can be the laser bird and have a snowball as a laser."
Son: "Cool! Let's go right away! Come on, dad!"
Malone's and Lepper's taxonomy of intrinsic motivation comprises four main motivating factors: challenge, curiosity, control, fantasy. Having a backstory provides a fantasy setting, and also provides material for curiosity, because one can explore how far the fantasy can be extended by using the play space, e.g., the snowballs. It can also inspire the child to come up with challenges. Many times, if I'm too tired to play cops and robbers, my son is happy to do all the running around by himself while I just sit on the couch and press imaginary buttons to control him on an imaginary iPad.
"Now I'm in level 13, and this is really hard. There's dynamite and I must not fall into the water (floor). Now press the button that makes me run to the door."
"You are the laser piggy. I must not hit the lasers."
Pretty contradictory considering that digital games are supposed to promote a sedentary lifestyle. Of course my son would never let go of the iPad voluntarily, but allowing him a controlled amount of daily gameplay seems to only boost his physical play by providing new backstories, similar to the books we read.
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