// opengl.cpp
//
// Copyright 1998 by David K. McAllister
//
// This file implements the API calls that draw particle groups in OpenGL.

#include "general.h"

#ifdef WIN32
// This is for something in gl.h.
#include <windows.h>
#else
#define NULL 0
#endif

#ifdef __APPLE__
#include <OpenGL/gl.h>
#else
#include <GL/gl.h>
#endif

// XXX #include <iostream.h>

extern "C" {

	// Emit OpenGL calls to draw the particles. These are drawn with
	// whatever primitive type the user specified(GL_POINTS, for
	// example). The color and radius are set per primitive, by default.
	// For GL_LINES, the other vertex of the line is the velocity vector.
	// XXX const_size is ignored.
	void pDrawGroupp(int primitive, bool const_size, bool const_color)
	{
		_ParticleState& _ps = _GetPState();

		// Get a pointer to the particles in gp memory
		ParticleGroup* pg = _ps.pgrp;

		if (pg == NULL)
			return; // ERROR

		if (pg->p_count < 1)
			return;

		if (primitive == GL_POINTS)
		{
			glPushClientAttrib(GL_CLIENT_VERTEX_ARRAY_BIT);
			glEnableClientState(GL_VERTEX_ARRAY);
			if (!const_color)
			{
				glEnableClientState(GL_COLOR_ARRAY);
				glColorPointer(4, GL_FLOAT, sizeof(Particle), &pg->list[0].color);
			}

			glVertexPointer(3, GL_FLOAT, sizeof(Particle), &pg->list[0].pos);
			glDrawArrays((GLenum)primitive, 0, pg->p_count);
			glPopClientAttrib();
			// XXX For E&S
			glDisableClientState(GL_COLOR_ARRAY);
		}
		else
		{
			// Assume GL_LINES
			glBegin((GLenum)primitive);

			if (!const_color)
			{
				for (int i = 0; i < pg->p_count; i++)
				{
					Particle& m = pg->list[i];

					// Warning: this depends on alpha following color in the Particle struct.
					glColor4fv((GLfloat*)&m.color);
					glVertex3fv((GLfloat*)&m.pos);

					// For lines, make a tail with the velocity vector's direction and
					// a length of radius.
					pVector tail = m.pos - m.vel;
					glVertex3fv((GLfloat*)&tail);
				}
			}
			else
			{
				for (int i = 0; i < pg->p_count; i++)
				{
					Particle& m = pg->list[i];
					glVertex3fv((GLfloat*)&m.pos);

					// For lines, make a tail with the velocity vector's direction and
					// a length of radius.
					pVector tail = m.pos - m.vel;
					glVertex3fv((GLfloat*)&tail);
				}
			}
			glEnd();
		}
	}

	void pDrawGroupl(int dlist, bool const_size, bool const_color, bool const_rotation)
	{
		_ParticleState& _ps = _GetPState();

		// Get a pointer to the particles in gp memory
		ParticleGroup* pg = _ps.pgrp;
		if (pg == NULL)
			return; // ERROR

		if (pg->p_count < 1)
			return;

		//if(const_color)
		//	glColor4fv((GLfloat *)&pg->list[0].color);

		for (int i = 0; i < pg->p_count; i++)
		{
			Particle& m = pg->list[i];

			glPushMatrix();
			glTranslatef(m.pos.x, m.pos.y, m.pos.z);

			if (!const_size)
				glScalef(m.size.x, m.size.y, m.size.z);
			else
				glScalef(pg->list[i].size.x, pg->list[i].size.y, pg->list[i].size.z);

			// Expensive! A sqrt, cross prod and acos. Yow.
			if (!const_rotation)
			{
				pVector vN(m.vel);
				vN.normalize();
				pVector voN(m.velB);
				voN.normalize();

				pVector biN;
				if (voN.x == vN.x && voN.y == vN.y && voN.z == vN.z)
					biN = pVector(0, 1, 0);
				else
					biN = vN ^ voN;
				biN.normalize();

				pVector N(vN ^ biN);

				double M[16];
				M[0] = vN.x;  M[4] = biN.x;  M[8] = N.x;  M[12] = 0;
				M[1] = vN.y;  M[5] = biN.y;  M[9] = N.y;  M[13] = 0;
				M[2] = vN.z;  M[6] = biN.z;  M[10] = N.z; M[14] = 0;
				M[3] = 0;     M[7] = 0;      M[11] = 0;   M[15] = 1;
				glMultMatrixd(M);
			}

			// Warning: this depends on alpha following color in the Particle struct.
			if (!const_color)
				glColor4fv((GLfloat*)&m.color);

			glCallList(dlist);

			glPopMatrix();
		}
	}
}