reflection.c

OpeNGL超级宝典源代码. OpeNGL超级宝典源代码.

// Reflection.c
// OpenGL SuperBible
// Demonstrates using blending/transparency
// Program by Richard S. Wright Jr.

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

// Light and material Data
GLfloat fLightPos[4]   = { -100.0f, 100.0f, 50.0f, 1.0f };  // Point source
GLfloat fLightPosMirror[4] = { -100.0f, -100.0f, 50.0f, 1.0f };
GLfloat fNoLight[] = { 0.0f, 0.0f, 0.0f, 0.0f };
GLfloat fLowLight[] = { 0.25f, 0.25f, 0.25f, 1.0f };
GLfloat fBrightLight[] = { 1.0f, 1.0f, 1.0f, 1.0f };

static GLfloat yRot = 0.0f;         // Rotation angle for animation        

        
//////////////////////////////////////////////////////////////////
// This function does any needed initialization on the rendering
// context. 
void SetupRC()
    {
    // Grayish background
    glClearColor(fLowLight[0], fLowLight[1], fLowLight[2], fLowLight[3]);
   
    // Cull backs of polygons
    glCullFace(GL_BACK);
    glFrontFace(GL_CCW);
    glEnable(GL_CULL_FACE);
    glEnable(GL_DEPTH_TEST);
    
    // Setup light parameters
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, fNoLight);
    glLightfv(GL_LIGHT0, GL_AMBIENT, fLowLight);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, fBrightLight);
    glLightfv(GL_LIGHT0, GL_SPECULAR, fBrightLight);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
     
    // Mostly use material tracking
    glEnable(GL_COLOR_MATERIAL);
    glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
    glMateriali(GL_FRONT, GL_SHININESS, 128);
    }


///////////////////////////////////////////////////////////
// Draw the ground as a series of triangle strips. The 
// shading model and colors are set such that we end up 
// with a black and white checkerboard pattern.
void DrawGround(void)
    {
    GLfloat fExtent = 20.0f;
    GLfloat fStep = 0.5f;
    GLfloat y = 0.0f;
    GLfloat fColor;
    GLfloat iStrip, iRun;
    GLint iBounce = 0;
    
    glShadeModel(GL_FLAT);
    for(iStrip = -fExtent; iStrip <= fExtent; iStrip += fStep)
        {
        glBegin(GL_TRIANGLE_STRIP);
            for(iRun = fExtent; iRun >= -fExtent; iRun -= fStep)
                {
                if((iBounce %2) == 0)
                    fColor = 1.0f;
                else
                    fColor = 0.0f;
                    
                glColor4f(fColor, fColor, fColor, 0.5f);
                glVertex3f(iStrip, y, iRun);
                glVertex3f(iStrip + fStep, y, iRun);
                
                iBounce++;
                }
        glEnd();
        }
    glShadeModel(GL_SMOOTH);
    }

///////////////////////////////////////////////////////////////////////
// Draw random inhabitants and the rotating torus/sphere duo
void DrawWorld(void)
    {
    glColor3f(1.0f, 0.0f, 0.0f);
    glPushMatrix();
        glTranslatef(0.0f, 0.5f, -3.5f);
    
        glPushMatrix();
            glRotatef(-yRot * 2.0f, 0.0f, 1.0f, 0.0f);
            glTranslatef(1.0f, 0.0f, 0.0f);
            glutSolidSphere(0.1f, 17, 9);
        glPopMatrix();

        
        glRotatef(yRot, 0.0f, 1.0f, 0.0f);
        gltDrawTorus(0.35, 0.15, 61, 37);

    glPopMatrix();
    }


///////////////////////////////////////////////////////////////////////        
// Called to draw scene
void RenderScene(void)
    {
    // Clear the window with current clearing color
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        
    glPushMatrix();
        // Move light under floor to light the "reflected" world
        glLightfv(GL_LIGHT0, GL_POSITION, fLightPosMirror);
        glPushMatrix();
            glFrontFace(GL_CW);             // geometry is mirrored, swap orientation
            glScalef(1.0f, -1.0f, 1.0f);
            DrawWorld();
            glFrontFace(GL_CCW);
        glPopMatrix();
    
        // Draw the ground transparently over the reflection
        glDisable(GL_LIGHTING);
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        DrawGround();
        glDisable(GL_BLEND);
        glEnable(GL_LIGHTING);
        
        // Restore correct lighting and draw the world correctly
        glLightfv(GL_LIGHT0, GL_POSITION, fLightPos);
        DrawWorld();
    glPopMatrix();
        
    // Do the buffer Swap
    glutSwapBuffers();
    }



///////////////////////////////////////////////////////////
// Called by GLUT library when idle (window not being
// resized or moved)
void TimerFunction(int value)
    {
    yRot += 1.0f;   // Update Rotation
    
    // Redraw the scene
    glutPostRedisplay();
    
    // Reset timer
    glutTimerFunc(1,TimerFunction, 1);
    }

void ChangeSize(int w, int h)
    {
    GLfloat fAspect;

    // Prevent a divide by zero, when window is too short
    // (you cant make a window of zero width).
    if(h == 0)
        h = 1;

    glViewport(0, 0, w, h);
        
    fAspect = (GLfloat)w / (GLfloat)h;

    // Reset the coordinate system before modifying
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
	
    // Set the clipping volume
    gluPerspective(35.0f, fAspect, 1.0f, 50.0f);
        
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();    
    glTranslatef(0.0f, -0.4f, 0.0f);
    }

/////////////////////////////////////////////////////////////
// Main program entrypoint
int main(int argc, char* argv[])
    {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(800,600);
    glutCreateWindow("OpenGL Blending and Transparency");
    glutReshapeFunc(ChangeSize);
    glutDisplayFunc(RenderScene);
    glutTimerFunc(10, TimerFunction, 1);
    
    SetupRC();
    glutMainLoop();

    return 0;
    }