select.c

OpeNGL超级宝典源代码. OpeNGL超级宝典源代码.

// Planets.c
// OpenGL SuperBible, 3rd Edition
// Richard S. Wright Jr.
// [e-mail]

#include "../../Common/OpenGLSB.h"	// System and OpenGL Stuff
#include <math.h>

struct Rectangle
	{
	int top;
	int bottom;
	int left;
	int right;
	};

///////////////////////////
// Object Names
#define TORUS	1
#define SPHERE	2
 
struct Rectangle boundingRect;	// Bounding rectangle
GLuint selectedObject = 0;		// Who is selected
float fAspect;					// Display aspect ratio


#if !defined(M_PI)
#define M_PI 3.14159265f
#endif

///////////////////////////////////////////////////////////
// Draw a torus (doughnut)  
// at z = 0... torus aligns with xy plane
void DrawTorus(int numMajor, int numMinor)
	{
    float majorRadius = 0.35F;
    float minorRadius = 0.15F;
    double majorStep = 2.0F*M_PI / numMajor;
    double minorStep = 2.0F*M_PI / numMinor;
    int i, j;
	float c, r, z;

	glEnable(GL_NORMALIZE);
    for (i=0; i<numMajor; ++i) 
		{
		double a0 = i * majorStep;
		double a1 = a0 + majorStep;
		GLfloat x0 = (GLfloat) cos(a0);
		GLfloat y0 = (GLfloat) sin(a0);
		GLfloat x1 = (GLfloat) cos(a1);
		GLfloat y1 = (GLfloat) sin(a1);

		glBegin(GL_TRIANGLE_STRIP);
		for (j=0; j<=numMinor; ++j) 
			{
			double b = j * minorStep;
			c = (float) cos(b);
			r = minorRadius * c + majorRadius;
			z = minorRadius * (GLfloat) sin(b);

			glTexCoord2f((float)i/(float)numMajor, (float)j/(float)numMinor);
			glNormal3f(x0*c, y0*c, z/minorRadius);
			glVertex3f(x0*r, y0*r, z);

			glTexCoord2f((float)(i+1)/(float)numMajor, (float)j/(float)numMinor);
			glNormal3f(x1*c, y1*c, z/minorRadius);
			glVertex3f(x1*r, y1*r, z);
			}
		glEnd();
		}
	glDisable(GL_NORMALIZE);
	}


///////////////////////////////////////////////////////////
// Just draw a sphere of some given radius
void DrawSphere(float radius)
	{
	GLUquadricObj *pObj;
	pObj = gluNewQuadric();
	gluQuadricNormals(pObj, GLU_SMOOTH);
	gluSphere(pObj, radius, 26, 13);
	gluDeleteQuadric(pObj);
	}


///////////////////////////////////////////////////////////
// Render the torus and sphere
void DrawObjects(void)
	{
	// Save the matrix state and do the rotations
	glMatrixMode(GL_MODELVIEW);
	glPushMatrix();

	// Translate the whole scene out and into view	
	glTranslatef(-0.75f, 0.0f, -2.5f);	

	// Initialize the names stack
	glInitNames();
	glPushName(0);

	// Set material color, Yellow
	// torus
	glColor3f(1.0f, 1.0f, 0.0f);
	glLoadName(TORUS);
	glPassThrough((GLfloat)TORUS);
	DrawTorus(40, 20);


	// Draw Sphere
	glColor3f(0.5f, 0.0f, 0.0f);
	glTranslatef(1.5f, 0.0f, 0.0f);
	glLoadName(SPHERE);
	glPassThrough((GLfloat)SPHERE);	
	DrawSphere(0.5f);

	// Restore the matrix state
	glPopMatrix();	// Modelview matrix
	}
	
///////////////////////////////////////////////////////////
// Called to draw scene
void RenderScene(void)
	{
	// Clear the window with current clearing color
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	
	// Draw the objects in the scene
	DrawObjects();

	// If something is selected, draw a bounding box around it
	if(selectedObject != 0)
		{
		int viewport[4];
		
		// Get the viewport
		glGetIntegerv(GL_VIEWPORT, viewport);

		// Remap the viewing volume to match window coordinates (approximately)
		glMatrixMode(GL_PROJECTION);
		glPushMatrix();
		glLoadIdentity();
		
		// Establish clipping volume (left, right, bottom, top, near, far)
		glOrtho(viewport[0], viewport[2], viewport[3], viewport[1], -1, 1);
		glMatrixMode(GL_MODELVIEW);

		glDisable(GL_LIGHTING);
		glColor3f(1.0f, 0.0f, 0.0f);
		glBegin(GL_LINE_LOOP);
			glVertex2i(boundingRect.left, boundingRect.top);
			glVertex2i(boundingRect.left, boundingRect.bottom);
			glVertex2i(boundingRect.right, boundingRect.bottom);
			glVertex2i(boundingRect.right, boundingRect.top);
		glEnd();
		glEnable(GL_LIGHTING);
		}

	glMatrixMode(GL_PROJECTION);
	glPopMatrix();
	glMatrixMode(GL_MODELVIEW);

	glutSwapBuffers();
	}



///////////////////////////////////////////////////////////
// Go into feedback mode and draw a rectangle around the object
#define FEED_BUFF_SIZE	32768
void MakeSelection(int nChoice)
	{
	// Space for the feedback buffer
	static GLfloat feedBackBuff[FEED_BUFF_SIZE];

	// Storage for counters, etc.
	int size,i,j,count;

	// Initial minimum and maximum values
	boundingRect.right = boundingRect.bottom = -999999.0f;
	boundingRect.left = boundingRect.top =  999999.0f;

	// Set the feedback buffer
	glFeedbackBuffer(FEED_BUFF_SIZE,GL_2D, feedBackBuff);

	// Enter feedback mode
	glRenderMode(GL_FEEDBACK);

	// Redraw the scene
	DrawObjects();

	// Leave feedback mode
	size = glRenderMode(GL_RENDER);

	// Parse the feedback buffer and get the
	// min and max X and Y window coordinates
	i = 0;
	while(i < size)
		{
		// Search for appropriate token
		if(feedBackBuff[i] == GL_PASS_THROUGH_TOKEN)
			if(feedBackBuff[i+1] == (GLfloat)nChoice)
			{
			i+= 2;
			// Loop until next token is reached
			while(i < size && feedBackBuff[i] != GL_PASS_THROUGH_TOKEN)
				{
				// Just get the polygons
				if(feedBackBuff[i] == GL_POLYGON_TOKEN)
					{
					// Get all the values for this polygon
					count = (int)feedBackBuff[++i]; // How many vertices
					i++;

					for(j = 0; j < count; j++)	// Loop for each vertex
						{
						// Min and Max X
						if(feedBackBuff[i] > boundingRect.right)
							boundingRect.right = feedBackBuff[i];

						if(feedBackBuff[i] < boundingRect.left)
							boundingRect.left = feedBackBuff[i];
						i++;

						// Min and Max Y
						if(feedBackBuff[i] > boundingRect.bottom)
							boundingRect.bottom = feedBackBuff[i];

						if(feedBackBuff[i] < boundingRect.top)
							boundingRect.top = feedBackBuff[i];
						i++;
						}
					}
				else
					i++;	// Get next index and keep looking
				}
			break;
			}
		i++;
		}
	}


///////////////////////////////////////////////////////////
// Process the selection, which is triggered by a right mouse
// click at (xPos, yPos).
#define BUFFER_LENGTH 64
void ProcessSelection(int xPos, int yPos)
	{
	// Space for selection buffer
	static GLuint selectBuff[BUFFER_LENGTH];

	// Hit counter and viewport storage
	GLint hits, viewport[4];

	// Setup selection buffer
	glSelectBuffer(BUFFER_LENGTH, selectBuff);
	
	// Get the viewport
	glGetIntegerv(GL_VIEWPORT, viewport);

	// Switch to projection and save the matrix
	glMatrixMode(GL_PROJECTION);
	glPushMatrix();

	// Change render mode
	glRenderMode(GL_SELECT);

	// Establish new clipping volume to be unit cube around
	// mouse cursor point (xPos, yPos) and extending two pixels
	// in the vertical and horizontal direction
	glLoadIdentity();
	gluPickMatrix(xPos, viewport[3] - yPos, 2,2, viewport);

	// Apply perspective matrix 
	gluPerspective(60.0f, fAspect, 1.0, 425.0);

	// Draw the scene
	DrawObjects();

	// Collect the hits
	hits = glRenderMode(GL_RENDER);

	// Restore the projection matrix
	glMatrixMode(GL_PROJECTION);
	glPopMatrix();

	// Go back to modelview for normal rendering
	glMatrixMode(GL_MODELVIEW);

	// If a single hit occurred, display the info.
	if(hits == 1)
		{
		MakeSelection(selectBuff[3]);
		if(selectedObject == selectBuff[3])
			selectedObject = 0;
		else
			selectedObject = selectBuff[3];
		}

	glutPostRedisplay();
	}



///////////////////////////////////////////////////////////
// This function does any needed initialization on the rendering
// context.  Here it sets up and initializes the lighting for
// the scene.
void SetupRC()
	{
	// Lighting values
	GLfloat  dimLight[] = { 0.1f, 0.1f, 0.1f, 1.0f };
	GLfloat  sourceLight[] = { 0.65f, 0.65f, 0.65f, 1.0f };
	GLfloat	 lightPos[] = { 0.0f, 0.0f, 0.0f, 1.0f };

	// Light values and coordinates
	glEnable(GL_DEPTH_TEST);	// Hidden surface removal
	glFrontFace(GL_CCW);		// Counter clock-wise polygons face out
	//glEnable(GL_CULL_FACE);		// Do not calculate insides

	// Enable lighting
	glEnable(GL_LIGHTING);

	// Setup and enable light 0
	glLightfv(GL_LIGHT0,GL_AMBIENT,dimLight);
	glLightfv(GL_LIGHT0,GL_DIFFUSE,sourceLight);
	glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
	glEnable(GL_LIGHT0);

	// Enable color tracking
	glEnable(GL_COLOR_MATERIAL);
	
	// Set Material properties to follow glColor values
	glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);

	// Gray background
	glClearColor(0.60f, 0.60f, 0.60f, 1.0f );
	glLineWidth(2.0f);
	}


///////////////////////////////////////////////////////////
// Set viewport and projection
void ChangeSize(int w, int h)
	{
	// Prevent a divide by zero
	if(h == 0)
		h = 1;

	// Set Viewport to window dimensions
    glViewport(0, 0, w, h);

	// Calculate aspect ratio of the window
	fAspect = (GLfloat)w/(GLfloat)h;

	// Set the perspective coordinate system
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	// Field of view of 45 degrees, near and far planes 1.0 and 425
	gluPerspective(60.0f, fAspect, 1.0, 425.0);

	// Modelview matrix reset
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	}

///////////////////////////////////////////////////////////
// Process the mouse click
void MouseCallback(int button, int state, int x, int y)
	{
	if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
		ProcessSelection(x, y);
	}

///////////////////////////////////////////////////////////
// Program entry point
int main(int argc, char* argv[])
	{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize(800,600);
	glutCreateWindow("Select an Object");
	glutReshapeFunc(ChangeSize);
	glutMouseFunc(MouseCallback);
	glutDisplayFunc(RenderScene);
	SetupRC();
	glutMainLoop();

	return 0;
	}