Aargh... I had wanted to do something like this, with triggers that set a
gravity direction and strength while you were within them, like a VPhysics
trigger. They're fun.
Well, looking at your post, I believe that there's no way in the world that I
would ever understand anything close to this.
> This is very very possible.
>
> Objectives and problems you have to overcome to meet this goal:
>
>
> - Use Quaternions to break Gimbal Locking (happens with Matrix and Euler
> Angles). You can download a nice set of Quaternion functions from Ogre
> Engine (free download) and with some slight tweaks they will work on
> Source. Quaternions are basically an Up Direction (vector), and an Angle
> (float). There is a function called "Slerp" that will let you smoothly
> orient between 2 quaternions. There are multiple ways to create
> Quaternions
> using Matrices or Vectors.
>
>
> - You'll have to keep a new vector that saves your "gravity direction".
> If you want to orient automatically you'll need to constantly trace
> downwards along your gravity direction and based on the new Ground Normal,
> allow orientation or not.
>
>
> - Source uses AABB which means your player box will never rotate, ever.
> This causes a problem with your origin. When you rotate onto a wall, your
> origin will be much closer to the ground than before. Simply hack around
> this by adjusting your RenderOrigin up X units off the ground (when you are
> on it of course).
>
>
> - Jumping was one of the bigger problems I first encountered. This is
> better suited for orientations based on events, if you want automatic
> orientation based on the ground the player is on, you'll need to have
> multiple traces of different lengths to make sure you maintain the correct
> orientation. You can also trigger going to a default gravity if you are in
> the air too long or the ground your over is to complicated or is orienting
> too fast.
>
>
> - You'll have to orient your models correctly. Models use Euler Angles
> for orientation, so if you use Quaternions, you'll have to convert to
> Matrix
> and then to Euler Angles. Not such a biggy, but Euler angles were never
> meant for 6 degrees of freedom usage. If you want to use them, only use
> them
> in the local world space where everything is oriented at (0,0,1). Then
> convert to world space.
>
>
> - Wall collision is another big problem you will encounter. Since you
> won't have the luxury of using the players bounding box for tracing, you'll
> have to be accurate with line traces. I constantly found myself getting
> knocked off the ground because of odd terrain. Stairs is another wall
> collision problem you have to face. This requires more line traces going
> in
> your movement direction starting from the top of your player model to the
> middle and so on. You have to make sure you can actually move forward if
> not
> you'll get yourself stuck in the terrain.
>
>
> - Other Entities is the last problem. So far you've only managed the
> players. Now you have to manage all other entity objects. You'll have to
> follow the same basic principles as the player orientation depending on
> what
> your entities do. Physics entities have to all orient based on the same
> gravity direction, if you want each one to have it's own orientation,
> you'll
> need to work with the physics interface. This requires managing the
> angular
> velocity and linear velocity. This is more complicated, and if you can
> pull off the player orientation, you should be able to figure a way to do
> this.
It would make for an awesome game though. Imagine a 1024 cube... Here's
looking forward to Ballmanmod.
Oh, and I recall that someone was asking why anti-gravity was not working
somewhere before.
It's because gravity is frozen for the player if they are standing on something
- just try setting negative gravity with sv_gravity.
Nothing happens to you if you're on the floor.
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