Reality Factory

Just want to let you know that I'm building physics into RF
and that it really start to work!

Furhtermore a ton of additional features where introduced (>70 features) and some known bugs resolved (eg the moving platform and door)

The physic topic is one of the most recurring in the forum. I want to start this trying to place a milestone in the continuous and partial circus of question and answer. I don’t know ALL the answer so help me to find the right way.

1) Reality Factory has his physic system derived by Genesis3d. Rigid body, gravity and bounding-box collision. We can’t define mass but we can use scripting command to apply forces: ForceForward, ForceBackward, ForceLeft, ForceRight, ForceUp, ForceDown.
There is extended physic in the projectile entitity, or the actorspout entity, setting true the Bounce parameters, but there is a strange inertia and can’t be scripted.
We can create rigid body joined together but we can’t add a joint between two entities.
Command for attaching actors: PositionToPawn PlayerToPosition PositionToPlayer and HighLevel command AttachToActor(“Entity Name”, “Slave Bone”, “Master Bone”, offset_X, offse, offset, rotation_X, rotation_Y, , rotation_Z) --- this must placed in the master pawn script in Spawn Order.
The collision works with bounding box (no triangle-triangle except the new static mesh entity). Note that this box don’t rotate with the actor. You can set only the width of a square as basis of the box, you can’t define the height.

2) Genesis3d has his physic system. Here we have the confusion, because even the genesis users (that people who really use c++ in games) haven’t a complete knowledge about this.
Here the most interesting topic:
http://www.genesis3d.com/~kdtop/Physics ... al%201.htm
http://www.genesis3d.com/~kdtop/Physics ... al%202.htm
http://www.genesis3d.com/~kdtop/Physics ... al%204.htm
What have I understood? …umh, you probably will need programming to make it work, but I read that GTest (or GDemo) has some physic entities. In the Header of entities for the world editor (that file in the “source” folder) there are three entities, if I correctly understood: PHYSICS_JOINTS: PHYSICS_OBJECTS: PHYSICAL_SYSTEMS:
So, instead ask to implement the complete Genesis3d physic in RF, we have to ask: “Is it difficult to implement these entity in RF?” Probably it is.

3) Scripted physic and new commands. Scripting a simple physic it’s not really difficult. Do you want to create a bouncing ball? Let’s make a script that ForceUp the pawn proportional to his time of falling. More time of falling = more reaction force.

{//ball.s

TIME [0]
FORCE [0]
FLYTIME [0]

Spawn[()
{
Console(true);
LowLevel("Setup");
}]

Setup[()
{
debug(FLYTIME);
if(self.IsFalling=true) // the pawn is flying
{
TIME=self.time; // all the time minus this time is the flying time
self.think="Fly";
}

if(IsKeyDown(7))
{
ForceUp(50);
}

if((FLYTIME*50)>20) // 20 is the lower limit for bounce
{
ForceUp(FLYTIME*50); // 50 is our coefficient for multiply the flying time
}
}]

Fly[()
{
debug(self.time-TIME); // keep the track of time

if(self.IsFalling=false) // stop tracking time
{
FLYTIME=self.time-TIME; //all the time minus that time is the flying time
self.think="Setup";
}

}]

}

Time is you friend. In this case Force+Time=Physic.
Dan Valeo created new commands for scripting a physic system that extend these possibilities. You can find it in the old forums but you have to rebuild RF with MSVC. He created a command to compute the distance bone to bone (yeah!), but essentially all these commands, new and old, are in the same family and you have to script a lot. Naturally a scripted physic is slow and not accurate.
In my racing demo, I made a scripted simulation of wheel sliding and sterring inertia using a complex way to handle the keyboard input. I set, via script, a latency in the keyboard input so the steering power increase and decrease progressively and so the engine torque etc.. Most of this script has been created in an “empirical way”, but basically is a complex (and useless for study) remake of my simplified “ball in the box “ demo.


4) External implementation. Greywolf started (but stopped) an attempt of implementation of external dll. There are several physic system like ODE that can be implemented in this way. Anyways it would be an really useful but potentially endless work.
http://www.realityfactory.ca/v4/viewtop ... sc&start=0

____________

Any idea?

Fede