www.pudn.com > Particles_OGL.zip > particle.cpp

#include "particle.h" 
#include "gl_obj.h" 
 
// Default constructor -- Zero everything out 
CParticle::CParticle() 
{ 
	color = ARGB(255, 255, 255, 255); 
	size = 0.0f; 
	life = 0.0f; 
	angle = 0.0f; 
	 
	// All other variables gets initialized with it's constructor 
} 
 
// Init the particle 
bool CParticle::init(const CPos &p, const CVector &v, float lifeSpan, float s, float a, int c, 
					 const char *texName) 
{ 
	pos = p; // Set the position 
	vel = v; // Set the velocity 
	 
	// Don't allow initialization of a "dead" particle  
	if(lifeSpan <= 0.0f) 
		return false; 
	 
	life = lifeSpan; // Set the time, in seconds, the particle will remain alive 
	 
	// Size must be positive 
	if(s <= 0.0f) 
		return false; 
		 
	size = s; // Set the size 
	angle = a; // Set the angle of texture UV rotation per second 
	color = c; // Set the color 
	 
	if(texName) // If a texture name was specified 
		return texture.load(texName); // Load the texture 
	else 
		return true; 
} 
 
void CParticle::process(float dt) 
{ 
	// If particle is dead, reset it's position 
	if(isAlive() == false) 
	{ 
		life = RAND(1.0f, 2.0f); // Make it alive again 
		pos = CPos(0,0,0); 
			return; 
	}		 
 
	// Apply velocity 
	pos.x += vel.x * dt; 
	pos.y += vel.y * dt; 
	pos.z += vel.z * dt; 
	 
	// Apply gravity 
	pos.y += kParticleGravity * dt; 
		 
	life -= dt; // Decrease particle's life span 
	 
	// Apply rotation by "angle" per second if applicable 
	if(angle != 0.0f) 
		texture.setRotation(texture.getRotAngle() + (angle * dt)); 
} 
 
void CParticle::render() 
{ 
	// If particle isn't alive, then there is nothing to render 
	if(isAlive() == false) 
		return; 
	 
	// Can't render a particle that does not have a valid texture  
	if(texture.getId() == TEXTURE_NOT_LOADED) 
		return; 
	 
	// This OpenGL functions makes the Z-buffer "read only".  That means OpenGL will 
	// use current z-buffer values to determine if a particle should be rendered or not, BUT, 
	// if it does render a particle it will NOT set any z-buffer values.  Why do we do this? 
	// Well we want the particles to blend, and not cover each other up.  So now we can 
	// render them in the same Z-depth and they will blend, but at the same time, they  
	// won't render over top of anything with a lesser Z-depth 
	glDepthMask(false); 
 
	// Set the color and texture for rendering 
	glColor4ub(GET_R(color), GET_G(color), GET_B(color), GET_A(color)); 
	texture.select(); 
	 
	glPushMatrix(); 
	 
		// Move to the world position of where to draw the particle 
		glTranslatef(pos.x, pos.y, pos.z); 
		 
		float halfSize = size * 0.5f; 
			 
		// Draw the particle 
		glBegin(GL_QUADS); 
			glTexCoord2f(0.0f, 1.0f); 
			glVertex3f(-halfSize, halfSize, 0.0f); // Top left vertex 
			 
			glTexCoord2f(0.0f, 0.0f); 
			glVertex3f(-halfSize, -halfSize, 0.0f); // Bottom left vertex 
			 
			glTexCoord2f(1.0f, 0.0f); 
			glVertex3f(halfSize, -halfSize, 0.0f); // Bottom right vertex 
			 
			glTexCoord2f(1.0f, 1.0f); 
			glVertex3f(halfSize, halfSize, 0.0f); // Top right vertex 
		glEnd(); 
		 
	glPopMatrix(); 
	 
	glDepthMask(true); // Put the Z-buffer back into it's normal "Z-read and Z-write" state 
}