(Note: I’m using a custom Quaternion class that consists of 4 floats however its the equivalent of a D3DXQuaternion)

Code sample:


Quaternion q1 = Quaternion::getIdentity();

Vector3 euler;
q1.getEulerAngles(euler);
Log("euler %f %f %f\n",euler.x,euler.y,euler.z);

This was the program output:

quat test #1 - angle-axis #1 0.802096 0.000476 0.597195 angle: 3.140315
euler 3.141136 0.001526 -1.280000


Notice, in the Euler conversion you can see a little bit of leakage into Roll. The problem is discussed in more detail here at StackOverflow forums. So it looks the general wisdom is to split up the incoming angles, track those separately, then generate the Quaternion from scratch every frame if you go this route. That really is a bloody shame however, since you are completely regenerating a Quaternion every frame. And worst, you later use this Quaternion to most likely rotate a view vector. If you use the traditional method to rotate a vector with a Quaternion you are not really using playing to its’ strength.

Code example:

Vector3 axis(0,1,0); //y-axis rotation
Quaternion q(axis, 1.28f); //angle in radians
q.rotate(ViewVector);


Funny thing is you can do the same exact thing with angle-axis like so (not to mention its faster to transform a Vector via a matrix):

Vector3 axis(0,1,0); //y-axis rotation
Matrix3 m(axis, 1.28f); //angle in radians
m.Mul(ViewVector);


However, since Quaternions are non-commutative you could first apply rotation along Y-axis and then pitch the quaternion via X-Axis. The resulting output in this case is a nice clean Quaternion like one might expect:


quat test #2 - angle-axis #1 0.000476 0.802096 -0.597195 angle: 3.140315
euler 1.280000 0.000000 3.140000


So, simply by applying the rotations in a different order we prevented the leakage. So it is possible to cleanly combine two quaternions and prevent unwanted leakage if you maintain the proper order. However, you can still get into trouble if you perform additional Quaternion math on this concatenated Quaternion later.

Here is an interesting trick though. If you take the Conjugate of the Unit Quaternion you will end up with an Inverse Quaternion. Take this Quaternion and generate a Matrix. If you later use this Matrix to get your Up & Right vectors you can continue to use concatenated Quaternions.


const Quaternion& GetRotation()
{
return m_rot;
}

//Inside the actor/camera class, use the Quaternion inverse to generate a matrix. However, store off your original Quaternion.
Quaternion q1 = q;
q1.conjugate();
q1.normalize();
QuaternionToMatrix(q1, m_quaternionInvMatrix); //Matrix generated using Quaternion inverse
}


Now you have a matrix that was built using the Quaternion inverse. You can actually use this as an actors rotation matrix (like for the spaceship, etc) and put in a 4×4 Matrix along with Translation. The cool thing is that you can also use this Quaternion later and navigate around leakage like so.


void Pitch(float angle)
{
Vector3 dir = m_quaternionInvMatrix.GetRight();
dir.Normalize();

Quaternion q = GetRotation();
q = q * t;
SetRotation(q);
}


Performing rotation along the Y-axis would be the exact same:

void RotateY(float angle)
{
Vector3 dir = m_quaternionInvMatrix.GetUp();
dir.Normalize();

Quaternion q = GetRotation();
q = q * t;
SetRotation(q);
}


Now you have an Actor that can accurately accumulate Quaternions in a fairly predictable manner. While I used it, I didn’t notice any leakage into Roll and everything worked nicely. I searched around the net for other topics on this but didn’t find anything. However, keep in mind you could also just go with 3×3 rotation matrices as well. Like Quaternions, you will evade the gimbal lock issue and many will find they are very ease to use.

Code example of using angle-axis which also avoids Gimbal Lock and will may possibly be superior to the Quaternion alternative for this purpose. Additionally, you can perform vector interpolation and weigh that against Quaternion::slerp if you like


void Pitch(float angle)
{
Vector3 dir = m_orientation.GetRight();
dir.Normalize();

Matrix3 tm(dir, -angle); //angle-axis to matrix
m_orientation *= tm;
}


Yeppers, this game is pure awesomeness. I’m sure I’ve drowned over 50+ hours into this game. I’ve still been playing although I’ve already beaten it. The game gets even more harder and there is more & more secrets to unlock. Highly replayable and highly worthy of a purchase if you don’t mind a little grinding and highly challenging gameplay. Another boon is that the PVP is actually quite amazing and addictive. I enjoyed the coop when others were nice enough to join albeit I wish it was easier to get help for some of these tough bosses espcially on NG+ (after you beat the game you can replay at a harder difficulty however you keep everything you earned on previous playthroughs).

If you don’t have a Playstation 3 then I must say this game should seriously give you a reason to buy one.

Right now the deferred renderer is noticeably slower than the forward renderer (you can hit a key to switch between the two). There’s a few optimizations I can do to speed up the deferred side but I do not expect it to match the forward renderer in performance. However, what deferred rendering brings to the table is a very nice dynamic, per pixel lighting system that can handle multiple lights with fair ease. If I were to try to hookup point lights to the forward renderer, I would have to spend a lot of effort managing the lights.

Ontop of that, no NPCs were available at the gang hideouts. So if you go to a hideout by yourself or with a posse, etc you’ll be awarded XP for completing the hideout. And due to the replay feature, you could basically go to a place like Fort Mercer and quickly maxout to Level 50. The ironic part is that I’m reading on the boards an xp nerf went out. Instead, I suspect a lot of people hit L50 (the inverse).

We’re planning to try again later tonight so my fingers will be crossed that most of the problems will be resolved.

Gamasutra had a very nice writeup about the game and the newly formed Haunted Temple Studios.

special thanks to gamespot for the image

Here are somethings to note however from the point of view of a multiplayer gamer. Since I’m playing with friends, I might not pay close attention to the plot. How can I when my friends are talking in the background during cutscenes? So I’ve actually been playing through some sections again to pay closer attention to the story. But still, even during the first play many bugs and shortcomings surfaced in this regard. You never see any lip movement during cutscenes. They sometimes pan in close into a face during a cutscene and the texture is just too low res for this.

The controls are just not very tight (maybe they weren’t in LP1 either). You cannot grapple unto surfaces in mid air for some baffling reason (would require more advanced physics like Just Cause 2?). You have to stop to switch weapons. The list goes on and on….

In multiplayer competitive online, you cannot play with friends basically. Sure, in Ranked Matches you can invite them but due to the lack of a party system the chances are high they’ll be tossed unto the opposite team. Very annoying.

Now if you try to exit the match early you’ll be slapped with DNF which I am guessing is some sort of negative rating. I’m indifferent towards it at the moment however it appears to contribute to people going afk during matches since they’re unable to leave. Free kills, though I guess.

In Lost Planet 1, a Host could choose the type of weapons and such for the match. But now, it doesn’t seem like you have a Host really. Everyone can vote on their favorite map and weapon layout. This is sort of an improvement but could be very bad if you are stuck with an all-sniper round. Sniping though, like in most shooters, can be problematic. Especially in this game where snipers seem to have clear aim almost right to the spawn spots. Granted, I believe there are strategies to deal with these guys I am sure. But it’s tough when you cant play the MP maps offline and run around to explore the map like you would in Halo 3, etc. This gives people a chance to explore a map, develop strategies, memorize where weapons are, etc. LP2 lacks all this so you have to learn it all on-the-fly with lots of bad guys shooting at ya.

I do love how you can unlock new pieces and such. But yeah, its annoying seeing your credits wasted on Emotes and such in the store due to the random rolls. In addition to this, if you’re not very good in the online competitive modes you’ll notice you get very little XP. Granted, Rainbow Six Vegas felt like a much more balanced game however it seemed much easier to earn great unlocks in the competitive modes.

Still it’s a very fun game for the time being and is worth at least a rent. The coop isn’t quite as refined as Left 4 Dead 1/2 however. Not being able to join an ongoing coop game is a bit of a bummer. Well you can join one, but you have to wait til they hit a checkpoint or something which can be a very long time or they have to wait at the lobby for others to join. The multiplayer features pale in comparison to games like Red Faction Guerrila and many others which include well done party systems for Clan vs Clan, etc.

Noticed we have 3 games on the horizon: Lost Planet 2 (just released) and Red Dead Redemption + Alan Wake. I don’t have time to play them all so difficult choices will have to be made….

Lost Planet 2 is getting destroyed in most of the reviews however 1UP gave it a favorable B+ score. 4 player coop is sooooo tempting….. However the lack of a Multiplayer party system for the online competitive modes might be a huge pain (in LP1 often times my friends and I had to fight against each other due to this huge oversight). On the other hand we have Red Dead Redemption which looks highly polished and features a fairly untapped western theme for multiplayer along with horses and a big sandbox feeling to it. Exploration has always been one of my favorite things to do in a game and this game seems to ooze that out….

Will no doubt end up buying all 3 but for now will have to decide what to focus on 1st…

Gamasutra just ran a news article on our publisher, THQ, which mentions Darksiders as a major contributing factor to a successful turnaround for the fiscal year.