// OPEN_GL_test.cpp : Defines the entry point for the console application.
//
// OPEN_GL_test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#define GL_PI 3.1415f

GLfloat xRot = 0.45f;
GLfloat yRot = 0.35f;
GLboolean bCull = glIsEnabled(GL_CULL_FACE);
GLboolean bDepth = glIsEnabled(GL_DEPTH_TEST);
GLboolean bOutline = (GLboolean)true;

GLenum shademode = GL_FLAT;

GLfloat ex = 0.0f;
GLfloat ey = 0.0f;
GLfloat ez = -120.0f;
GLfloat delta = 0.01f;
GLfloat deltaR = 0.01f;


///////////////////////////////////////////////////////////


void SetupRC()
{
	// Black background
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

	// Set drawing color to green
	glColor3f(0.0f, 1.0f, 0.0f);

	// Set color shading model to flat
	glShadeModel(shademode);

	// Clockwise-wound polygons are front facing; this is reversed
	// because we are using triangle fans
	glFrontFace(GL_CW);
}

// Called to draw scene

void RenderScene(void)
{
	// Reset coordinate system

	glLoadIdentity();
	gluLookAt(ex, ey, ez, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

	GLfloat x, y, angle;         // Storage for coordinates and angles
	int iPivot = 1;            // Used to flag alternating colors

							   // Clear the window and the depth buffer
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	// Turn culling on if flag is set
	if (bCull)   glEnable(GL_CULL_FACE);
	else        glDisable(GL_CULL_FACE);

	// Enable depth testing if flag is set
	if (bDepth)  glEnable(GL_DEPTH_TEST);
	else        glDisable(GL_DEPTH_TEST);

	// Draw the back side as a wireframe only, if flag is set
	if (bOutline)glPolygonMode(GL_BACK, GL_LINE);
	else        glPolygonMode(GL_BACK, GL_FILL);

	// Save matrix state and do the rotation
	glPushMatrix();
	glRotatef(xRot, 1.0f, 0.0f, 0.0f);
	glRotatef(yRot, 0.0f, 1.0f, 0.0f);

	// Begin a triangle fan
	glBegin(GL_TRIANGLE_FAN);

	// Pinnacle of cone is shared vertex for fan, moved up z-axis
	// to produce a cone instead of a circle
	glVertex3f(0.0f, 0.0f, 75.0f);

	// Loop around in a circle and specify even points along the circle
	// as the vertices of the triangle fan

	for (angle = 0.0f; angle < (2.0f*GL_PI); angle += (GL_PI / 8.0f))

	{
		// Calculate x and y position of the next vertex
		x = 50.0f*sin(angle);
		y = 50.0f*cos(angle);

		// Alternate color between red and green

		if ((iPivot % 2) == 0)    glColor3f(0.0f, 1.0f, 0.0f);
		else			        glColor3f(1.0f, 0.0f, 0.0f);

		// Increment pivot to change color next time
		iPivot++;

		// Specify the next vertex for the triangle fan
		glVertex2f(x, y);
	}

	// Done drawing fan for cone
	glEnd();

	// Begin a new triangle fan to cover the bottom
	glBegin(GL_TRIANGLE_FAN);

	// Center of fan is at the origin
	glVertex2f(0.0f, 0.0f);

	for (angle = 0.0f;  angle < (2.0f*GL_PI);    angle += (GL_PI / 8.0f))
	{
		// Calculate x and y position of the next vertex
		x = 50.0f*sin(angle);
		y = 50.0f*cos(angle);

		// Alternate color between red and green
		if ((iPivot % 2) == 0)
			glColor3f(0.0f, 1.0f, 0.0f);
		else
			glColor3f(1.0f, 0.0f, 0.0f);

		// Increment pivot to change color next time
		iPivot++;

		// Specify the next vertex for the triangle fan
		glVertex2f(x, y);
	}

	// Done drawing the fan that covers the bottom
	glEnd();

	// Restore transformations
	glPopMatrix();

	// Flush drawing commands
	glFlush();//glutSwapBuffers();
}

// Called by GLUT library when the window has changed size

void ChangeSize(GLsizei w, GLsizei h)
{    // Set Viewport to window dimensions
	glViewport(0, 0, (GLsizei)w, (GLsizei)h);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	//glOrtho (-100.0, 100.0, -100, 100, -270.0, 270.0);
	//glFrustum (-1.0, 1.0, -1.0, 1.0, 1.5, 20.0);
	gluPerspective(60.0, 1.0, 1.5, 500.0);
	glMatrixMode(GL_MODELVIEW);
}



void SpecialKeys(int key, int x, int y)
{
	GLfloat dx, dz;


	if (key == GLUT_KEY_UP)
	{//increase distance from camera to origin
		ex *= (1.0f + deltaR);  ey *= (1.0f + deltaR);	ez *= (1.0f + deltaR);
	}

	if (key == GLUT_KEY_DOWN)
	{//reduce distance from camera to origin (close up)
		ex *= (1.0f - deltaR); ey *= (1.0f - deltaR);	ez *= (1.0f - deltaR);
	}

	if (key == GLUT_KEY_LEFT)
		//Rotate camera around origin in Oxz plane
	{
		dx = -ez;     dz = ex;
		GLfloat s = sqrtf(ex*ex + ey*ey + ez*ez);
		ex += delta*dx;       ez += delta*dz;
		GLfloat s1 = sqrtf(ex*ex + ey*ey + ez*ez) / s;
		ex /= s1;	ey /= s1;	ey /= s1;
	}

	if (key == GLUT_KEY_RIGHT)
		//Rotate camera around origin in Oxz plane
	{
		dx = -ez;     dz = ex;
		GLfloat s = sqrtf(ex*ex + ey*ey + ez*ez);
		ex -= delta*dx;      	ez -= delta*dz;
		GLfloat s1 = sqrtf(ex*ex + ey*ey + ez*ez) / s;
		ex /= s1;	ey /= s1;	ey /= s1;
	}


	if (key == GLUT_KEY_F1) bCull = !bCull;
	if (key == GLUT_KEY_F2)bDepth = !bDepth;
	if (key == GLUT_KEY_F3)bOutline = !bOutline;
	if (key == GLUT_KEY_F4)
	{
		if (shademode == GL_FLAT) { shademode = GL_SMOOTH; }
		else { if (shademode == GL_SMOOTH) { shademode = GL_FLAT; } };
		glShadeModel(shademode);
	}
	// Refresh the Window
	glutPostRedisplay();


	// Refresh the Window
	glutPostRedisplay();
}


///////////////////////////////////////////////////////////



int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(/*GLUT_DOUBLE*/GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(200, 200);
	glutInitWindowPosition(100, 100);
	glutCreateWindow(argv[0]);
	glutDisplayFunc(RenderScene);
	glutReshapeFunc(ChangeSize);
	glutSpecialFunc(SpecialKeys);

	SetupRC();
	glutMainLoop();
	return 0;
}