gePhysicsSystem *PS;

gePhysicsObject *PO;

geXForm3d Xform;

geExtBox ExtBox;

geActor *Actor;

BOOL Running = TRUE;

DWORD Timer1 = timeGetTime();

DWORD Timer2 = Timer1;

geVec3d OldVec,NewVec;

GE_Collision Col;



// Load an actor

LoadActor(Actor,"Dema.act");



geXForm3d_SetIdentity(&Xform);

geActor_GetDynamicExtBox(Actor,&ExtBox);



// Create physics system

PS  =  gePhysicsSystem_Create();



//  Create physics object

PO  = gePhysicsObject_Create(&Xform.Translation,1.0f,GE_TRUE,GE_TRUE,0.00005f,0.00005f,&ExtBox.Min,&ExtBox.Max,1.0f);



// Add physics object to physics system

gePhysicsSystem_AddObject(PS,PO);



// Set physics object XForm

gePhysicsObject_SetXForm(PO, &Xform, 0);



// physics and rendering loop

while(Running)

{

     

    // This is used to limit the number of times the physics are updated

    // The time used will entierly depend on your program

    // Basiclly this make the physics independent of rendering

    if ((timeGetTime()-Timer1) > 2)

    {

          // reset the timer 

          Timer1 = timeGetTime();



          // Save the xform's position before updating

          OldVec = Xform.Translation;



          // Update the physics system, the largest number is 0.03f and

          // it only makes a differance if physics joints are added to the physics system.

          // This function will call gePhysicsObject_ComputeForces() and

          // gePhysicsObject_Integrate() for every physics object in the physics system. 



          gePhysicsSystem_Iterate(PS,0.03f);

                

          // Get the updated XForm

          gePhysicsObject_GetXFormInEditorSpace(PO, &Xform, 0);

           

          // save the xform's position after updating

          NewVec = Xform.Translation;



          // test if there was a collision

          if (geWorld_Collision(World,&ExtBox.Min,&ExtBox.Max,&OldVec,&NewVec,GE_CONTENTS_SOLID_CLIP,GE_COLLIDE_ALL,0xffffffff,NULL,NULL,&Col))

          {

                // Collision found do something



                Xform.Translation = Col.Impact;

                gePhysicsObject_SetXForm(PO, &Xform, 0);

          }

          

          // Set actors xform

          geActor_ClearPose(Actor, &Xform);



    }



    // Limit rendering to 30 FPS

    // This is needed because physics are slow and when

    // trying to render every frame the physics slows to a crawl

    if ((timeGetTime()-Timer2)>34)

    {

          Timer2=timeGetTime();



          if (!geEngine_BeginFrame(Engine, Camera, GE_TRUE))

             Running = 0;

          if (!geEngine_RenderWorld(Engine, World, Camera, 0.0f))

             Running = 0;

          if (!geEngine_EndFrame(Engine))

             Running = 0;

     }



}

One thing though, is I could really learn from seeing hot to handle the collision between two actors as it relates to the physics system. I'm really unclear on that, since the physics system doesn't do the collision. So I am unclear what information I need to gather from the collion, and how/what to pass on to the physics system.

A question. If you are ding your physics, seperately from the main loop, wouldn't that cause problems with it bien gupdated more often then everythign else? I.E. An object falling further than it should because the gravity was applied twice for only one pass of the main loop?

.

.

.

    if ((timeGetTime()-Timer1) > 30)

    {

          Timer1 = timeGetTime();

          OldVec = Xform.Translation;

          gePhysicsSystem_Iterate(PS,0.03f);

.

.

.

.

.

.

while(Running)

{

     

    OldVec = Xform.Translation;



    gePhysicsSystem_Iterate(PS,(float)(timeGetTime()-Timer1)/1000);



    Timer1 = timeGetTime();



    gePhysicsObject_GetXFormInEditorSpace(PO, &Xform, 0);

.

.

.

Actually, I don't see how the second method is goign to take more power. If you limit your rendering loop to 30FPS, and your PhysicsIterate is based on your rendering loop, then it too should only be calced 30FPS.

And in actuality, basing it on delta time coudl SAVE cpu time..What if a render loop takes a bit longer? Then instead of still doing it every 30ms, you might actually do a few less calcs that cyle, just with a longer iteration.

On 2001-08-31 00:57, securitron wrote:
there may be a problem with the timer1 and the > sign. if rendering takes awhile then the test at timer 1 could be way off imo

Well, now I'm lost. I had essentially the exact same thing set up to do gravity for my actors but it didn't work. The only difference between this and what I did was I didn't use a gePhysicsSystem. I just create a gePhysicsObject for my actor and then I called gePhysicsObject_ComputeForces and gePhysicsObject_Integrate myself instead of using the gePhysicsSystem_Iterate to do it. But mine doesn't work. The actor floats above the ground never going down. Weird.

// Needed for high performance counter

static void SubLarge(LARGE_INTEGER *start, LARGE_INTEGER *end, LARGE_INTEGER *delta)

{

	_asm {

		mov ebx,dword ptr [start]

		mov esi,dword ptr [end]



		mov eax,dword ptr [esi+0]

		sub eax,dword ptr [ebx+0]



		mov edx,dword ptr [esi+4]

		sbb edx,dword ptr [ebx+4]



		mov ebx,dword ptr [delta]

		mov dword ptr [ebx+0],eax

		mov dword ptr [ebx+4],edx

	}

}







// sample physics system

void Physics()

{





    LARGE_INTEGER CurTick,DeltaTick,OldTick,Freq;

    float ElapsedTime;

    gePhysicsSystem *PS;

    gePhysicsObject *PO;

    geXForm3d Xform;

    geExtBox ExtBox;

    geActor *Actor;

    int ConfigIndex = 0;

    BOOL Running = TRUE;

    DWORD Timer = timeGetTime();

    geVec3d OldVec,NewVec;

    GE_Collision Col;

    

    // Load an actor

    LoadActor(Actor,"Dema.act");



    geXForm3d_SetIdentity(&Xform);

    geActor_GetDynamicExtBox(Actor,&ExtBox);



    // Create physics system

    PS  =  gePhysicsSystem_Create();



    //  Create physics object

    PO  = gePhysicsObject_Create(&Xform.Translation,1.0f,GE_TRUE,GE_TRUE,0.00005f,0.00005f,&ExtBox.Min,&ExtBox.Max,1.0f);



    // Add physics object to physics system

    gePhysicsSystem_AddObject(PS,PO);



    // Set physics object XForm

    gePhysicsObject_SetXForm(PO, &Xform, 0);



    // Needed for high performance counter

    QueryPerformanceFrequency(&Freq);

    QueryPerformanceCounter(&OldTick);



    // physics and rendering loop

    while(Running)

    {

     

                

        // Save the xform's position before updating

        OldVec = Xform.Translation;



        //High performace counter

        QueryPerformanceCounter(&CurTick);

        SubLarge(&OldTick, &CurTick, &DeltaTick);	

        OldTick = CurTick;		

        if (DeltaTick.LowPart > 0)

            ElapsedTime =  1.0f / (((float)Freq.LowPart / (float)DeltaTick.LowPart));

        else

            ElapsedTime = 0.001f;



        // Update the physics system, the largest number is 0.03f and

        // This function will call gePhysicsObject_ComputeForces() and

        // gePhysicsObject_Integrate() for every physics object in the physics system. 

        gePhysicsSystem_Iterate(PS,ElapsedTime);



        // Get The current config index for the physics system

        ConfigIndex = gePhysicsSystem_GetSourceConfigIndex(PS);



        // Get the updated XForm

        gePhysicsObject_GetXFormInEditorSpace(PO, &Xform, ConfigIndex);

           

        // save the xform's position after updating

        NewVec = Xform.Translation;



        // test if there was a collision

        if (geWorld_Collision(World,&ExtBox.Min,&ExtBox.Max,&OldVec,&NewVec,GE_CONTENTS_SOLID_CLIP,GE_COLLIDE_ALL,0xffffffff,NULL,NULL,&Col))

        {

              // Collision found do something



              Xform.Translation = Col.Impact;

              gePhysicsObject_SetXForm(PO, &Xform, ConfigIndex);

        }

     

		

        // Set actors xform

        geActor_ClearPose(Actor, &Xform);



      			

        // Limit rendering to 30 FPS

        // This is needed because physics are slow and when

        // trying to render every frame the physics slows to a crawl

        if ((timeGetTime()-Timer)>=34)

        {

            Timer=timeGetTime();



            if (!geEngine_BeginFrame(Engine, Camera, GE_TRUE))

               Running = 0;

            if (!geEngine_RenderWorld(Engine, World, Camera, 0.0f))

               Running = 0;

            if (!geEngine_EndFrame(Engine))

               Running = 0;

        }

    }



}

jeff lol now i'm going to whinge about exactly the same thing *again*, i'm still not sold on the way that you are controlling the FPS with that check on the timer ( its the > sign that bugs me ).

right, i know that your calculations come out correctly, what i meant i guess, was that it shouldn't imo be in the physics procedure, not sure if that was intentional or just for testing...

have a constant in my ge_physicsobject.pas ( your PhysicsObject.c supposedly) that was 'automatically' generated out by neils delphi generator:

const
PHYSOB_GRAVITY: gefloat = (-3.9)

and appears that it is never called.