/*
	glparticle.cpp - Particle system
	Copyright (c) HalfLucifer, 2002.3.1
*/
#include "glparticle.h"


GLparticle::GLparticle()
{
	m_NumParticle = 2000;
	m_Size = 50.0f;
	m_Radius = 0.1f;
	m_Gravity = 5.0f;
	m_Bounce = 0.4f;
	m_EnergyDrop = 0.01f;
	m_BirthVelocity = 25.0f;
}

GLparticle::~GLparticle()
{
	delete [] m_ParticlePool;
}

bool GLparticle::Initialize()
{
	srand(GetTickCount());

	m_Color = GLvector((float)(rand()%256)/255, (float)(rand()%256)/255, (float)(rand()%256)/255);
	m_Texture.LoadJPG("particle.jpg");
	m_ParticlePool = new Particle[m_NumParticle];
	if (!m_ParticlePool)
		return false;

	return true;
}

void GLparticle::Update()
{
	for (int i=0; i<m_NumParticle; i++)
	{
		m_ParticlePool[i].position += m_ParticlePool[i].velocity;
		m_ParticlePool[i].energy -= m_EnergyDrop;

		if (m_ParticlePool[i].position[1] > m_Radius)
			m_ParticlePool[i].position[1] -= m_Gravity;
		else
		{
			m_ParticlePool[i].position[1] = m_Radius;
			m_ParticlePool[i].velocity[1] = -m_ParticlePool[i].velocity[1];
			m_ParticlePool[i].velocity *= m_Bounce;
		}

		if (m_ParticlePool[i].energy <= 0)
		{
			m_ParticlePool[i].position = m_Position;
			m_ParticlePool[i].energy = 1.0f;

			float alpha = 2 * (float)GLPi * rand()/RAND_MAX;
			float beta  = (float)GLPi * ((float)rand()/RAND_MAX - 0.5f); 
			m_ParticlePool[i].velocity[0] = (float)(m_BirthVelocity * cos(beta) * sin(alpha));
			m_ParticlePool[i].velocity[1] = (float)(m_BirthVelocity * sin(beta));
			m_ParticlePool[i].velocity[2] = (float)(m_BirthVelocity * cos(beta) * cos(alpha));
		}
	}
}

void GLparticle::Render()
{
	GLvector v;
	GLvector up = camera.GetUpVector();
	GLvector right = camera.GetRightVector();

	glBlendFunc(GL_ONE, GL_ONE);
	glEnable(GL_BLEND);
	glDisable(GL_DEPTH_TEST);
	glDisable(GL_LIGHTING);
	glBindTexture(GL_TEXTURE_2D, m_Texture.ID());

	for (int i=0; i<m_NumParticle; i++)
	{
		v = m_Color * m_ParticlePool[i].energy;
		glColor3fv(v);
		glPushMatrix();
			glTranslatef(m_ParticlePool[i].position[0], m_ParticlePool[i].position[1], m_ParticlePool[i].position[2]);
			if (g_billboard)
			{
				glBegin(GL_TRIANGLES);
					v = up*(-m_Size/2) + right*(-m_Size);
					glTexCoord2f(0.0f, 0.0f);
					glVertex3fv(v);
					v = up*(-m_Size/2) + right*m_Size;
					glTexCoord2f(1.0f, 0.0f);
					glVertex3fv(v);
					v = up*m_Size/2;
					glTexCoord2f(0.5f, 0.75f);
					glVertex3fv(v);
				glEnd();
			}
			else
			{
				glBegin(GL_TRIANGLES);
					glTexCoord2f(0.0f, 0.0f);
					glVertex3f(-m_Size, -m_Size/2, 0.0f);
					glTexCoord2f(1.0f, 0.0f);
					glVertex3f(m_Size, -m_Size/2, 0.0f);
					glTexCoord2f(0.5f, 0.75f);
					glVertex3f(0.0f, m_Size/2, 0.0f);
				glEnd();
			}
		glPopMatrix();
	}

	glEnable(GL_LIGHTING);
	glEnable(GL_DEPTH_TEST);
	glDisable(GL_BLEND);
	glColor3f(1.0f, 1.0f, 1.0f);
}

void GLparticle::SetEmitterPos(GLvector &pos)
{
	m_Position = pos;
	m_Target = pos;
}

void GLparticle::MoveEmitterPos(GLvector &pos)
{
	m_Target = pos;
}

void GLparticle::SetColor(GLvector &color)
{
	m_Color = color;
}

void GLparticle::SetNum(int num)
{
	if (num > 0)
	{
		delete [] m_ParticlePool;
		m_NumParticle = num;
		m_ParticlePool = new Particle[m_NumParticle];
	}
}