3. PhysX Scenes

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Here’s our third PhysX tutorial, and it doesn’t look like we are getting anywhere, but this tutorial is going to start getting into the PhysX SDK. We are going to create a scene which will calculate all our physics interactions. Just like OpenGL needs a window to draw to, PhysX needs a scene to simulate a world with. But don’t interperet this wrong, the PhysX SDK DOES NOT do any rendering for you.

So, continuing on from the previous tutorial, we need to create a new global variable that will be the scene for our PhysX world. This is going to be called gScene, and takes the type NxScene. We will set it like so:

// NxScene* gScene = NULL;

So we have a scene, what do we do with it? First off we are going to set the most basic of properties, gravity. So we need to create a scene descriptor which will hold the properties for our scene. We are going to start off with creating a variable for our scene descriptor called sceneDesc like so:

NxSceneDesc sceneDesc;

Now that we have a scene descriptor, we need to set our gravity:

// sceneDesc.gravity.set(0.0f, -9.8f, 0.0f);

And now we are going to create our scene:

// gScene = gPhysicsSDK->createScene(sceneDesc);

So we now have a scene that we can add objects to, and adjust its properties as needed. Eg: In the game Prey, we change the gravity direction throughout to allow for a new type of gameplay.

To close up our program, we need to go to our deinitNX function and release our scene:

// gPhysicsSDK->releaseScene(*gScene);
// gScene = 0;

So we now have a scene, in our next tutorial we are going to start playing with some different parameters. You can check it out here.

If you have any questions, just email me at swiftless@gmail.com

#include <stdio.h>

#include <GL\glut.h>
#include <GL\gl.h>

#include <Physics\include\NxPhysics.h>

#define NOMINMAX

#include <windows.h>

#pragma comment(lib,"PhysXLoader.lib")
#pragma comment(lib,"NxCharacter.lib")
#pragma comment(lib,"NxCooking.lib")

#pragma comment(lib,"NxExtensions.lib")

static NxPhysicsSDK* gPhysicsSDK = NULL;

NxScene* gScene = NULL;

void initNX(void){
gPhysicsSDK = NxCreatePhysicsSDK(NX_PHYSICS_SDK_VERSION);

NxSceneDesc sceneDesc;
sceneDesc.gravity.set(0.0f, -9.8f, 0.0f);
gScene = gPhysicsSDK->createScene(sceneDesc);
}

void deinitNX(void){

gPhysicsSDK->releaseScene(*gScene);
gScene = 0;

gPhysicsSDK->release();
}

void display(void){

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glLoadIdentity();

glutSwapBuffers();
}

void reshape(int w, int h){
glViewport(0,0, (GLsizei)w, (GLsizei)h);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60, (GLfloat)w / (GLfloat)h, 0.1f, 100.0f);
glMatrixMode(GL_MODELVIEW);
}

int main(int argc, char** argv) {

glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_STENCIL);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow("Physics");

initNX();

glutDisplayFunc(display);
glutIdleFunc(display);
glutReshapeFunc(reshape);

glutMainLoop();

deinitNX();

return 0;
}

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Download main.cpp Source Code for this Tutorial

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