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 Grasshopper4k  (Read 3235 times) 0 Members and 1 Guest are viewing this topic.
soothsayer

Senior Newbie

Projects: 1

 « Posted 2009-02-18 10:02:14 »

I always wanted to write some car racing game. Not really small size game, but finally this is the issue. Now everyone can create a game with an almost realistic car. I got the idea from APE engine however I simplified collision detection because it was too difficult.

Until deadline 10 days have remained yet. Try to write a better game, for instance  better car or terrain generation etc.

http://users.atw.hu/cppanddelphi/grasshopper4k/A.java

See below the physics model. Joints and constraints. Maybe this is the best arrangement, but you can experience with the structure.

zeroone
 « Reply #1 - Posted 2009-02-18 15:30:56 »

Can you provide a better explanation of how your physics engine works?  This is really cool stuff.
soothsayer

Senior Newbie

Projects: 1

 « Reply #2 - Posted 2009-02-18 16:51:47 »

First of all the surface, the particle and the constraint parts should remain unchanged. These are essential parts.

One can create model structure on simple way.

See the variables

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33 ` // Surfaces (n pieces depends terrain)  private float[][] S = new float[65535][6];  // 0 = point1X   // 1 = point1Y   // 2 = point2X   // 3 = point2Y   // 4 = surface normal X   // 5 = surface normal Y  // Particles (7 pieces)  private float[][] P = new float[7][14];  // 0 = is active   // 1 = current position X   // 2 = current position Y   // 3 = previous position X   // 4 = previous position Y   // 5 = effective force X   // 6 = effective force Y  // 7 = particle radius   // other auxiliary variables  // 8 = tempX   // 9 = tempY   // 10 = closestPointX   // 11 = closestPointY   // 12 = correctionX   // 13 = correctionY  // Constraints (18 pieces)  private float[][] C = new float[18][4];  // 0 = index1   // 1 = index2   // 2 = restlength   // 3 = stiffness`

If you create a surface just give 2 points. Be careful, the normal of surface determines a half plane. A surface is effective if the the particle is on the same side of this half plane. Particles and constraints should be above the surfaces.

If you create a particle just give a particle number, x and y coordinates and a radius. Every particle is active by default. In the given code the first particle not active, so collision detection skip it.

If you create a constraint just give a constraint number and particles number, between these particles the constraint is situated. At last the stiffness value.

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27 `    particleCreate(0, -65,  -30, 1.15f);    particleCreate(1,   0,  -30, 0.5f); P[1][0] = 0;    particleCreate(2,  65,  -30, 1.15f);    particleCreate(3,  65,  -70, 0.85f);    particleCreate(4,  30, -100, 1.15f);    particleCreate(5, -30, -100, 1.15f);    particleCreate(6, -65,  -70, 0.85f);    constraintCreate(0, 0, 1, 0.25f);    constraintCreate(1, 1, 2, 0.25f);    constraintCreate(2, 2, 3, 0.25f);    constraintCreate(3, 3, 4, 0.25f);    constraintCreate(4, 4, 5, 0.25f);    constraintCreate(5, 5, 6, 0.25f);    constraintCreate(6, 6, 0, 0.25f);    constraintCreate(7, 0, 3, 0.15f);    constraintCreate(8, 0, 4, 0.15f);    constraintCreate(9, 0, 5, 0.15f);    constraintCreate(10, 1, 3, 0.15f);    constraintCreate(11, 1, 4, 0.15f);    constraintCreate(12, 1, 5, 0.15f);    constraintCreate(13, 1, 6, 0.15f);    constraintCreate(14, 2, 4, 0.15f);    constraintCreate(15, 2, 5, 0.15f);    constraintCreate(16, 2, 6, 0.15f);    constraintCreate(17, 3, 6, 0.15f);`

One engine step is fulfilled the following way. Go through all particles and constraints with particleVerlet() and constraintResolve() procedure.

Finally check particles and surfaces collision. If there are a lot of surface then collision detection is very time consuming. It worths to perform some space partitioning procedure.

 1  2  3  4  5  6  7  8  9  10  11  12  13  14 `        int delta = (int) (System.currentTimeMillis() - lastLoopTime);        lastLoopTime = System.currentTimeMillis();        for (k = 0; k < delta / 15; k++)        {          // timestep          for (i = 0; i < 7; i++)  // particles (7)            particleVerlet(i);          for (i = 0; i < 18; i++)  // constraints (18)            constraintResolve(i);          for (j = 0; j < surfaceCount; j++)  // surfaces (surfaceCount)            for (i = 0; i < 7; i++)  // particles (7)              particleCheckCollision(j, i);        }`

One thing is missing. The forces.
Forces must take effect parallel with vector which indicate form point 0 to point 2.

 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32 `  private void HandleKeyEvent()  {    float dist, vX, vY;    dist = (float)distance(P[0][1], P[0][2], P[2][1], P[2][2]);    vX = (P[2][1] - P[0][1]) / dist;    vY = (P[2][2] - P[0][2]) / dist;    if (K[KeyEvent.VK_UP])    {      P[0][5] = vX * 2.75f;      P[0][6] = vY * 2.75f;      P[2][5] = vX * 2.75f;      P[2][6] = vY * 2.75f;    };    if (K[KeyEvent.VK_DOWN])    {      {        P[0][5] = vX * -1.75f;        P[0][6] = vY * -1.75f;        P[2][5] = vX * -1.75f;        P[2][6] = vY * -1.75f;      }    };    if (! K[KeyEvent.VK_DOWN] && ! K[KeyEvent.VK_UP])    {      P[0][5] = 0;      P[0][6] = 0;      P[2][5] = 0;      P[2][6] = 0;    };  }`

cylab

JGO Wizard

Medals: 135

 « Reply #3 - Posted 2009-02-19 08:59:08 »

Doesn't seem to do anything here with one cpu core 100% load.

JDK 6 u12 (32Bit)
Core 2 Duo P9500 2.53Ghz
9800M GTS
Forceware 185.20

Mathias - I Know What [you] Did Last Summer!
soothsayer

Senior Newbie

Projects: 1

 « Reply #4 - Posted 2009-02-19 10:20:06 »

I am afraid cylab I do not know what is the problem.

Perhaps run the program without antialiasing.
cylab

JGO Wizard

Medals: 135

 « Reply #5 - Posted 2009-02-19 10:38:50 »

Thats very odd. I ran the code in the Netbeans profiler and it rund fine, while running it normally, it stalls...

Mathias - I Know What [you] Did Last Summer!
cylab

JGO Wizard

Medals: 135

 « Reply #6 - Posted 2009-02-19 10:42:20 »

Adding a Thread.sleep(10) at the end of the main loop did the trick. It seems your tight loop has eaten away the AWT-Thread.

Mathias - I Know What [you] Did Last Summer!
soothsayer

Senior Newbie

Projects: 1

 « Reply #7 - Posted 2009-02-19 12:59:42 »

Thank you very much. I will complete the code soon.
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