So, I have got a very simple problem. (I am 11 so please try not to use so much trigonometry...) I have got an Opengl project, I call it "Paintball". It is supporsed to be an FPS. You have got a gun (MS3D model) and when you shoot, I find the intersection point of sector and the view vector and I render particles there (explosion from NeHe tutorials). So this is the code that renders the particle: #ifdef BILLBOARD glBegin(GL_TRIANGLE_STRIP); glTexCoord2d(0,0); glVertex3f(x + (-right.x - up.x), y + (-right.y - up.y), z + (-right.z - up.z)); glTexCoord2d(1,0); glVertex3f(x + ( right.x - up.x), y + ( right.y - up.y), z + ( right.z - up.z)); glTexCoord2d(1,1); glVertex3f(x + ( right.x + up.x), y + ( right.y + up.y), z + ( right.z + up.z)); glTexCoord2d(0,1); glVertex3f(x + (-right.x + up.x), y + (-right.y + up.y), z + (-right.z + up.z)); glEnd(); //CRASH 1 #else glBegin(GL_TRIANGLE_STRIP); glTexCoord2d(1,1); glVertex3f(x+0.2f,y+0.2f,z); glTexCoord2d(0,1); glVertex3f(x-0.2f,y+0.2f,z); glTexCoord2d(1,0); glVertex3f(x+0.2f,y-0.2f,z); glTexCoord2d(0,0); glVertex3f(x-0.2f,y-0.2f,z); glEnd(); //CRASH 2 #endif I call this code in a FOR cycle. If I define BILLBOARD, so the application crashes on the line //CRASH 1. If I dont, it crashes on the line //CRASH 2, but it doesnt crash in the first cycle. Doesnt anybody know how to solve this problem? Thanks.

Just out of curiosity why are you using preproccessor?

I use preprocessor because I have got two variations of my application: with billboarding (realistic) and without it (fast).

I did.

It crashed later, it was this font drawing function:

void Font_drawtext( bool sada, int xpos, int ypos, int size, char *str, ... )
{
glDisable(GL_DEPTH_TEST); // Disables Depth Testing
char buffer[1024];
int i, L, ascii;
float cx, cy;
memset(buffer, '\0', 1024);
va_list argptr;
va_start( argptr, str );
_vsnprintf( buffer, 1024, str, argptr );
va_end( argptr );
L = strlen( buffer );
glCallList( fontsavestate );
glTranslatef( (float)xpos, (float)ypos, 0 );
for( i=0; i<L; i++ ) {
ascii = (int)buffer;
if( buffer == '&' && i+1<L )
{
glColor3f(1.0f,0.0f,0.0f);
continue;
}
else {
cx=float(ascii%16)/16.0f;
cy=(float(ascii/16)/16.0f)+((sada)?(0.5):(0));
glBegin( GL_QUADS );
glTexCoord2f( cx,1-cy-0.0625f );
glVertex2i( 0,0 );
glTexCoord2f( cx+0.0625f,1-cy-0.0625f );
glVertex2i( size,0 );
glTexCoord2f( cx+0.0625f,1-cy );
glVertex2i( size,size );
glTexCoord2f( cx,1-cy );
glVertex2i( 0,size );
glEnd(); // <-- CRASH POINT!
glTranslatef( (float)size, 0, 0 );
}
}
glCallList( fontrestorestate );
glEnable(GL_DEPTH_TEST); // Enables Depth Testing
}

There was another glEnd before this funcion, but it WASNT in pair with glBegin(GL_QUADS). Maybe the matter is the GL_QUADS.

So, this is the code rendering the particles. I am too lazy to remove the comments so please dont worry about non-english comments. They are in Czech. (a little country in center of Europe)

glBlendFunc(GL_SRC_ALPHA,GL_ONE);// Typ blendingu
glBindTexture(GL_TEXTURE_2D,texture_particles);// Vybere texturu

camera.Look();

glColor3f(1.0f,1.0f,1.0f);

#ifdef BILLBOARD
const float width = 0.1f;// Polovina velikosti
const float height = 0.1f;
float mat[16];
glGetFloatv(GL_MODELVIEW_MATRIX, mat);
CVector3 right=CVector3(mat[0], mat[4], mat[8]);
right=Normalize(right);
right = right * width;
CVector3 up=CVector3(mat[1], mat[5], mat[9]);
up=Normalize(up);
up = up * height;
#endif

for (loop=0;loop<MAX_PARTICLES;loop++)// Cyklus prochází každou èástici
{
if (particle[loop].active)// Pokud je èástice aktivní
{
// Vykreslení
float x=particle[loop].x;// x pozice
float y=particle[loop].y;// y pozice
float z=particle[loop].z;// z pozice + zoom

#ifdef BILLBOARD
// Vykreslení
glBegin(GL_TRIANGLE_STRIP);
glTexCoord2d(0,0);
glVertex3f(x + (-right.x - up.x),
y + (-right.y - up.y),
z + (-right.z - up.z));
glTexCoord2d(1,0);
glVertex3f(x + ( right.x - up.x),
y + ( right.y - up.y),
z + ( right.z - up.z));
glTexCoord2d(1,1);
glVertex3f(x + ( right.x + up.x),
y + ( right.y + up.y),
z + ( right.z + up.z));
glTexCoord2d(0,1);
glVertex3f(x + (-right.x + up.x),
y + (-right.y + up.y),
z + (-right.z + up.z));
glEnd();
#else
glBegin(GL_TRIANGLE_STRIP);// Vytvoøí obdélník pomocí triangle strip
glTexCoord2d(1,1); glVertex3f(x+0.2f,y+0.2f,z);// Horní pravý
glTexCoord2d(0,1); glVertex3f(x-0.2f,y+0.2f,z);// Horní levý
glTexCoord2d(1,0); glVertex3f(x+0.2f,y-0.2f,z);// Dolní pravý
glTexCoord2d(0,0); glVertex3f(x-0.2f,y-0.2f,z);// Dolní levý
glEnd();// Ukonèí triangle strip
#endif



particle[loop].x+=particle[loop].xi/(slowdown*1000);// Pohyb na ose x
particle[loop].y+=particle[loop].yi/(slowdown*1000);// Pohyb na ose y
particle[loop].z+=particle[loop].zi/(slowdown*1000);// Pohyb na ose z
particle[loop].xi+=1.8f;// Gravitaèní pùsobení na ose x
particle[loop].yi+=1.8f;// Gravitaèní pùsobení na ose y
particle[loop].zi+=1.8f;// Gravitaèní pùsobení na ose z
particle[loop].life-=particle[loop].fade;// Sníží život o stárnutí
if (particle[loop].life<0.0f) particle[loop].active=false;
}
}


The particles are from NeHe lesson XX (Particle System). You can find there english comments.