OgreNewt 2        
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This page is still "under development"! There may be some less correct information, feel free to update it :-) --SFCBias?September 30, 2010

Using Ogre with OgreNewt 2.0 = OgreNewt

Note:
Look also to the old page OgreNewt, because this new page doesn't contain all information. Especially look to the section Newton SDK in a Nutshell.

Introduction

In this page is here to help you to jump into OgreNewt 2.0 with OGRE v1.7 For this we will use OgreNewt.

Most of the information about Newton is on OgreNewt, so for now this page will hold only some Newton 2.0 specific info. You should take a look at that page first, so you can get a better idea about Newton.

Requirements:

  1. OGRE v1.7 Cthugha - OGRE3D official page(external link)
  2. Newton 2.19 Or above - Newton official page(external link)
  3. OgreNewt - OGRE SVN(external link) you need to use this version.
  4. Cmake 2.8 Cmake Official Site(external link)

 
UPDATE:
Newton 2.33 wrapper(external link)

Compiling OgreNewt

First download OgreNewt from the svn and extract it to a place you can remember.To compile OgreNewt you need to open cmake and set it to point to your OgreNewt source and set the binary path to /newton20/bin (Its easier this way). Click "Configure".It will ask for what kind of build files you want. Choose whats appropriate for your system. There will be red values, If any errors about Not finding paths just click that selection and set it to point to that path. (If any it's usually Ogre Samples dir). You should then have build files. Generated in your binary path. Open them and compile. Or for Linux makefiles, open the dir in terminal and type 'make' then 'sudo make install'.

How to set up your project

{TODO}

Simple Application

Here I will explain how to set up a simple OgreNewt application. For this we will use the ExampleApplication provided with the OgreSDK.

Creating the base classe

First lets set-up our base class. We will use an header and a source file for our class.

Our header (OgreNewtApplication.h) should start like this:

#ifndef __OgreNewtApplication_h_
 #define __OgreNewtTut_h_
 
 #include <OgreNewt.h>
 #include "ExampleApplication.h"
 
 class OgreNewtApplication :
     public ExampleApplication
 {
 public:
     OgreNewtApplication(void);
     ~OgreNewtApplication(void);
 
     void createScene();
 
     void createFrameListener(void);
 };
 
 #endif

This is just like what you use one the Ogre Tutorials. Don't forget to add #include <OgreNewt.h> or else we can't use OgreNewt

Now that we have our base header, we can start working on the source file. So, our source file (OgreNewtApplication.cpp) should start like this:

#include "OgreNewtApplication.h"
 
 
 OgreNewtApplication::OgreNewtApplication(void)
 {
 }
 
 OgreNewtApplication::~OgreNewtApplication(void)
 {
 } 
 
 void OgreNewtApplication::createScene()
 { 
     Ogre::Light *light = mSceneMgr->createLight("main_light");
     light->setPosition(0, 50, 0);
     light->setDiffuseColour(Ogre::ColourValue(1, 0.5, 0.5));
     mSceneMgr->setAmbientLight(Ogre::ColourValue(0.5,0.5,0.5));
 
     mCamera->setPosition(Ogre::Vector3(100,50,100));
     mCamera->lookAt(0,0,0);
 }
 
 void OgreNewtApplication::createFrameListener()
 { 
 }

Setting-up OgreNewt

 

First of all we need a Newton world, so add this to the header file, just before the end of the class ( }; )

private:
     OgreNewt::World *mWorld;

(After this point we won't change the header any more)

Then we need to actually create the world, so inside the constructor of the class add this:

mWorld = new OgreNewt::World();

This is needed to create all the objects from OgreNewt.

Then add this line to the destructor of the class, to make sure the world gets destroyed in the end.

delete mWorld;

One last thing we need to be able to do something is to create two frame listeners: the one that you see in most of the demos and tutorials, that reads input, updates camera movement, etc. and other to update the Newton world.

So first lets add the "normal" frame listener. Add this to the createFrameListener() function of our OgreNewtApplication class:

mFrameListener = new ExampleFrameListener( mWindow, mCamera );
     mRoot->addFrameListener( mFrameListener );

Now we will add the OgreNewt frame listener. OgreNewt (like Ogre) provides us with a simple frame listener to update our physics. We will use that in this tutorial, but you should create your own if your developing a more complex application.

So, add this inside the createFrameListener() function, just after the last frame listener:

OgreNewt::BasicFrameListener* mOgreNewtListener;
     mOgreNewtListener = new OgreNewt::BasicFrameListener( mWindow, mCamera, mSceneMgr, mWorld, 120 );
     mRoot->addFrameListener( mOgreNewtListener );

Try to compile your project now. If you get some linker errors on the OgreNewt::BasicFrameListener creation, just add the OgreNewt_BasicFrameListener.h and OgreNewt_BasicFrameListener.cpp from OgreNewt source to your project, and add #include <OgreLogManager.h> #include <OgreStringConverter.h> to the source file, and it should be fine. This should be fixed quick tough.

Creating the scene

Now that everything is set-up correctly, we should start adding some stuff to our empty scene.

First we will create a ground, so the objects have something to fall into.

Let's create the visual object. Add this to the OgreNewtApplication::createScene() function:

Ogre::Vector3 size(10.0,1.0,10.0);
     Ogre::SceneNode* node = mSceneMgr->getRootSceneNode()->createChildSceneNode();
     Ogre::Entity* ent = mSceneMgr->createEntity( "floorobj", "box.mesh" );
     node->attachObject( ent );
     node->setScale( size );

Now we need to make a rigid physics body that represents this object. This is made of two steps: first we create a collision primitive, the we create a Body from that collision.

Let's make the collision then.

OgreNewt::CollisionPtr col( new OgreNewt::CollisionPrimitives::TreeCollision( mWorld, ent, true));

This will create a TreeCollision. Since this floor will never move, we create a TreeCollision, but we could also create a box.

The first parameter is the OgreNewt::World to add this collision to. The second is the entity that this collision represents, the TreeCollision is made with the shape of the entity passed, and retrieves the orientation, position and scale from the entity's parent node. The third parameter is weather Newton should try to optimise this TreeCollision or not.

Remember, if you want to change the object scale, set the scale on the node, create a new Collision Primitive from it and add it to the body.

Now let's create a rigid Body for this Collision:

OgreNewt::Body* floorbody = new OgreNewt::Body( mWorld, col );
     floorbody->attachNode(node);

This creates the Body and attaches the SceneNode to it. If this was not a TreeCollision body, if it was a movable kind of body, every time it was moved by Newton, it's scene node position and orientation would update!

Lets now set the position of this floor:

floorbody->setPositionOrientation( Ogre::Vector3(0,-5,0), Ogre::Quaternion::IDENTITY );

Now we will create a movable body! A little box:

// BOX
     size = Ogre::Vector3( 10, 10, 10 );
     node = mSceneMgr->getRootSceneNode()->createChildSceneNode();
     ent = mSceneMgr->createEntity("box_body", "box.mesh" );
     node->attachObject( ent );
     node->setScale( size );
 
     // rigid body.
     OgreNewt::CollisionPrimitives::Box *boxcol = new OgreNewt::CollisionPrimitives::Box(mWorld, size);
     col = OgreNewt::CollisionPtr(boxcol);
     OgreNewt::Body* bod = new OgreNewt::Body( mWorld, col );
     bod->attachNode( node );
 
     // initial position
     bod->setPositionOrientation( Ogre::Vector3(-2,20,2), Ogre::Quaternion::IDENTITY );

This is similar to what we have done to create our floor! The only change is that we create a Box collision primitive here. The first parameter is the OgreNewt::World. Second is the size of the box. Third is orientation, optional. Fourth is position, optional too.

Now, since we want to move this body, we need some other things, like mass, inertia moment and center of mass. Mass is any value you like, inertia is more complicated. Luckly, Newton provides us a way to get the inertia and center of mass. Add this to your code:

Ogre::Real mass = 10.0;
     Ogre::Vector3 inertia, centerOfMass;
     boxcol->calculateInertialMatrix(inertia, centerOfMass);
 
     inertia*=mass;    
 
     bod->setMassMatrix( mass, inertia );
     bod->setCenterOfMass(centerOfMass);

Just one last thing. If we don't add any forces to our body, it would not move! So let's add some gravity.

OgreNewt provides a simple way to do this:

bod->setStandardForceCallback();

Now our body is "ready to go"!

Let's just create two more bodies to fill up our scene.

// CYLINDER  
     // cylinder with a radius of 5.5, height of 10.3
     size = Ogre::Vector3( 10.3, 5.5, 5.5 );
     node = mSceneMgr->getRootSceneNode()->createChildSceneNode();
     ent = mSceneMgr->createEntity("cylinder_body", "cylinder.mesh" );
     node->attachObject( ent );
     node->setScale( size );
 
     // rigid body.
     OgreNewt::CollisionPrimitives::Cylinder *cylCol = new OgreNewt::CollisionPrimitives::Cylinder(mWorld, 5.5, 10.3);
     col = OgreNewt::CollisionPtr(cylCol);
     bod = new OgreNewt::Body( mWorld, col );
     bod->attachNode( node );
 
     // initial position
     bod->setPositionOrientation( Ogre::Vector3(20,15,15), Ogre::Quaternion(Ogre::Degree(45),Ogre::Vector3(1,1,0)) );
 
     mass = 5.0;
     cylCol->calculateInertialMatrix(inertia, centerOfMass);
 
     inertia*=mass;    
 
     bod->setMassMatrix( mass, inertia );
     bod->setCenterOfMass(centerOfMass);
 
     bod->setStandardForceCallback();
 
     // CONE
     // cone with a radius of 4.8, height of 5.0
     size = Ogre::Vector3( 5.0, 4.8, 4.8 );
 
     node = mSceneMgr->getRootSceneNode()->createChildSceneNode();
     ent = mSceneMgr->createEntity("cone_body", "cone.mesh" );
     node->attachObject( ent );
     node->setScale( size );
 
     // rigid body.
     OgreNewt::CollisionPrimitives::Cone *coneCol = new OgreNewt::CollisionPrimitives::Cone(mWorld, 4.8, 5.0);
     col = OgreNewt::CollisionPtr(coneCol);
     bod = new OgreNewt::Body( mWorld, col );
     bod->attachNode( node );
 
     // initial position
     bod->setPositionOrientation( Ogre::Vector3(0,26,5), Ogre::Quaternion(Ogre::Degree(45), Ogre::Vector3(1,0,0)) );
 
     mass = 15.0;
     coneCol->calculateInertialMatrix(inertia, centerOfMass);
 
     inertia*=mass;    
 
     bod->setMassMatrix( mass, inertia );
     bod->setCenterOfMass(centerOfMass);
 
     bod->setStandardForceCallback();

That's it! If you run the application now you should see three bodies falling! :-)

Creating a custom force callback

Now that you know how the basics, let's try to create our custom force callback! To add forces to a body you need a custom force callback.

First go to your header file OgreNewtApplication.h and declare this function there:

void crazyCallback(OgreNewt::Body* body, float timeStep, int threadIndex );

That function needs to have that three parameters and return void. The first parameter is the body that this callback is applied to (it could be applied to more than one body, and will be called for each body). The second one is the timeStep since the last call. The third is the index of the thread running the call, I think, but I'm not sure of that (as far as I know, OgreNewt is not thread safe, so for now this third parameter does not matter much I guess).

Now let's go to the source file OgreNewtApplication.cpp and implement that function. If anyone wants to add a more interesting force callback, please do --DeadVirus? 17:59, 4 July 2009 (UTC)

void OgreNewtApplication::crazyCallback(OgreNewt::Body *body, float timeStep, int threadIndex)
 {
     Ogre::Vector3 force(0,10,0), pointToApply(4,4,4);
     body->addLocalForce(force, pointToApply);
 }

This applies a force on position (4,4,4) relative to the body.

Now we need to actually set this callback on a body (or more).

Go to the OgreNewtApplication::createScene() and create another body:

// CONE
     // cone with a radius of 4.8, height of 10.0
     size = Ogre::Vector3( 10.0, 4.8, 4.8 );
 
     node = mSceneMgr->getRootSceneNode()->createChildSceneNode();
     ent = mSceneMgr->createEntity("crazy_cone_body", "cone.mesh" );
     node->attachObject( ent );
     node->setScale( size );
 
     // rigid body.
     coneCol = new OgreNewt::CollisionPrimitives::Cone(mWorld, 4.8, 5.0);
     col = OgreNewt::CollisionPtr(coneCol);
     bod = new OgreNewt::Body( mWorld, col );
     bod->attachNode( node );
 
     // initial position
     bod->setPositionOrientation( Ogre::Vector3(20,26,5), Ogre::Quaternion::IDENTITY );
 
     mass = 20.0;
     coneCol->calculateInertialMatrix(inertia, centerOfMass);
 
     inertia*=mass;    
 
     bod->setMassMatrix( mass, inertia );
     bod->setCenterOfMass(centerOfMass);
 
     bod->setCustomForceAndTorqueCallback<OgreNewtApplication>(&OgreNewtApplication::crazyCallback, this);

We've just created another cone that will rotate because of the force that we applied. Remember that it will not fall because we are not applying any gravity force.

To syntax to set a custom force callback is:

body->setCustomForceAndTorqueCallback<class_having_callback>(&class_having_callback::callback_function, initialized pointer to class_having_callback);

That's it! Easy, right?

Tutorial code

Here you can find the code for this tutorial.

See Also

 


Alias: Newton Game Dynamics 2.0


Contributors to this page: jacmoe177744 points  , SFCBias198 points  , OgreWikiBot54 points  and Beauty14435 points  .
Page last modified on Monday 01 of August, 2011 00:21:12 UTC by jacmoe177744 points .


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