Helloy everybody, I started with Nehe's Tutorial #19 this morning and implemented the particle system in my application. It works fine after some "adaptions", but now I realize, that my particles won't "burn out", I mean, they are created, they fly their way across the screen or whatever and then they suddenly disappear. But in the lesson application, the particles fade out gradually on their way. I checked everything to my knowledge and can't seem to find out why they won't fade out gradually in my version. Here is the init_particles ( ) function to initialize the particle system:
void init_particles ( void )
// initializes the particle system
{
// setup the particle system
for ( int loop = 0; loop < MAX_PARTICLES; loop++ )
{
// activate the particle
particle[loop].active = true;
// give it full life
particle[loop].life = 1.0f;
// give it a random fade speed
particle[loop].fade = float ( rand ( ) % 100 ) / 1000.0f + 0.003f;
particle[loop].r = fire_color[rand ( ) % 4][0];
particle[loop].g = fire_color[rand ( ) % 4][1];
particle[loop].b = fire_color[rand ( ) % 4][2];
// give it a random speed
particle[loop].xi = float ( ( rand ( ) % 50 ) - 25.0f ) * 10.0f;
particle[loop].yi = float ( ( rand ( ) % 50 ) - 25.0f ) * 10.0f;
particle[loop].zi = float ( ( rand ( ) % 50 ) - 25.0f ) * 10.0f;
// give it an upward gravity
particle[loop].xg = 0.0f;
particle[loop].yg = 0.6f;
particle[loop].zg = 0.0f;
}
}
And here is the draw_particles ( ) function, that draws the particles and updates their movement etc. It gets called by my draw_scene ( ) function every frame.
void draw_particles ( float x, float y, float z )
// draws particles at a specific location
{
// move for the particle system test
glTranslatef ( x, y, z );
// disable depth testing
glDisable ( GL_DEPTH_TEST );
// enable blending
glEnable ( GL_BLEND );
// select blending type
glBlendFunc ( GL_SRC_ALPHA, GL_ONE );
for ( int loop = 0; loop < MAX_PARTICLES; loop++ )
// loop through all particles
{
if ( particle[loop].active )
// if the particle is active
{
float x = particle[loop].x;
float y = particle[loop].y;
float z = particle[loop].z;
// set texture for particle
glBindTexture ( GL_TEXTURE_2D, texture[2] );
// set color and transparency for particle
glColor4f ( particle[loop].r, particle[loop].g, particle[loop].b, particle[loop].life );
// build quad from triangle strip
glBegin ( GL_TRIANGLE_STRIP );
glTexCoord2d ( 1, 1 ); glVertex3f ( x + 0.5f, y + 0.5f, z );
glTexCoord2d ( 0, 1 ); glVertex3f ( x - 0.5f, y + 0.5f, z );
glTexCoord2d ( 1, 0 ); glVertex3f ( x + 0.5f, y - 0.5f, z );
glTexCoord2d ( 0, 0 ); glVertex3f ( x - 0.5f, y - 0.5f, z );
glEnd ( );
// move the particle according to his speed
particle[loop].x += particle[loop].xi / ( 2.0f * 1000 );
particle[loop].y += particle[loop].yi / ( 2.0f * 1000 );
particle[loop].z += particle[loop].zi / ( 2.0f * 1000 );
// move the particle according to his gravity
particle[loop].xi += particle[loop].xg;
particle[loop].yi += particle[loop].yg;
particle[loop].zi += particle[loop].zg;
// reduce life by fade
particle[loop].life -= particle[loop].fade;
if ( particle[loop].life < 0.0f )
// if the particle is burned out
{
// give it new life and a random fade value
particle[loop].life = 1.0f;
particle[loop].fade = float ( rand ( ) % 100 ) / 1000.0f + 0.003f;
// center it
particle[loop].x = 0.0f;
particle[loop].y = 0.0f;
particle[loop].z = 0.0f;
// give it new speed and direction
particle[loop].xi = float ( ( rand ( ) % 60 ) - 30.0f );
particle[loop].yi = float ( ( rand ( ) % 60 ) - 30.0f );
particle[loop].zi = float ( ( rand ( ) % 60 ) - 30.0f );
// select new color
particle[loop].r = fire_color[rand ( ) % 4][0];
particle[loop].g = fire_color[rand ( ) % 4][1];
particle[loop].b = fire_color[rand ( ) % 4][2];
}
}
}
// reset color and transparency again
//glColor4f ( 1.0f, 1.0f, 1.0f, 1.0f );
// enable depth testing again
glEnable ( GL_DEPTH_TEST );
// and disable blending again
glDisable ( GL_BLEND );
}
I commented out the third line from the end in the draw_function ( ), but uncommenting it doesn't change a thing. Maybe I should also mention that my particles don't get the color they are supposed to take. It's almost like my glColor ( ) function does not get executed, but I couldn't find anything about this issue in either the tutorial or the OpenGL reference. Thanks, Jan.
