OpenGL-GLUT tutorial (8) glut scenario Roaming II

GLUT Tutorial Keyboard example ------ Scenario roaming II  In this section, let's take a look at the previous example. This time we will use advanced keyboard control. In the initialization section, we have two variables: deltaangle and deltamode. These variables control rotation and movement of cameras. When the value is not 0, the camera performs some operations. When the value is 0, the camera does not move. The initial values of these two variables are 0, that is, the initial state of the camera does not move.

#include <math.h>

#include <GL/glut.h>

float angle=0.0,deltaAngle = 0.0,ratio;

float x=0.0f,y=1.75f,z=5.0f;

float lx=0.0f,ly=0.0f,lz=-1.0f;

GLint snowman_display_list;

int deltaMove = 0;

void changeSize(int w, int h)

         {

         // Prevent a divide by zero, when window is too short

         // (you cant make a window of zero width).

         if(h == 0)

                 h = 1;

         ratio = 1.0f * w / h;

         // Reset Projection Matrix

         glMatrixMode(GL_PROJECTION);

         glLoadIdentity();

         // Set the size of the view.

         glViewport(0, 0, w, h);

         // Set the visible space

         gluPerspective(45,ratio,1,1000);

         glMatrixMode(GL_MODELVIEW);

         glLoadIdentity();

         gluLookAt(x, y, z, 

                       x + lx,y + ly,z + lz,

                           0.0f,1.0f,0.0f);

         }

void drawSnowMan() {

         glColor3f(1.0f, 1.0f, 1.0f);

// Draw Body     

         glTranslatef(0.0f ,0.75f, 0.0f);

         glutSolidSphere(0.75f,20,20);

// Draw Head

         glTranslatef(0.0f, 1.0f, 0.0f);

         glutSolidSphere(0.25f,20,20);

// Draw Eyes

         glPushMatrix();

         glColor3f(0.0f,0.0f,0.0f);

         glTranslatef(0.05f, 0.10f, 0.18f);

         glutSolidSphere(0.05f,10,10);

         glTranslatef(-0.1f, 0.0f, 0.0f);

         glutSolidSphere(0.05f,10,10);

         glPopMatrix();

// Draw Nose

         glColor3f(1.0f, 0.5f , 0.5f);

         glRotatef(0.0f,1.0f, 0.0f, 0.0f);

         glutSolidCone(0.08f,0.5f,10,2);

}

GLuint createDL() {                          //Returns a display list.

         GLuint snowManDL;

         // Create the id for the list

         snowManDL = glGenLists(1);

         // start list

         glNewList(snowManDL,GL_COMPILE);

         // call the function that contains 

         // the rendering commands

                 drawSnowMan();

         // endList

         glEndList();

         return(snowManDL);

}

void initScene() {

         glEnable(GL_DEPTH_TEST);

         snowman_display_list = createDL();

}

void orientMe(float ang) {

         lx = sin(ang);

         lz = -cos(ang);

         glLoadIdentity();

         gluLookAt(x, y, z, 

                       x + lx,y + ly,z + lz,

                           0.0f,1.0f,0.0f);

}

void moveMeFlat(int i) {

         x = x + i*(lx)*0.1;

         z = z + i*(lz)*0.1;

         glLoadIdentity();

         gluLookAt(x, y, z, 

                       x + lx,y + ly,z + lz,

                           0.0f,1.0f,0.0f);

}

The following code is different from the previous one. The following function first checks whether the two variables we define are 0. If it is not 0, the corresponding function is called to control the movement and rotation of the camera.

void renderScene(void) {

         if (deltaMove)

                 moveMeFlat(deltaMove);

         if (deltaAngle) {

                 angle += deltaAngle;

                 orientMe(angle);

         }

         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Draw ground

         glColor3f(0.9f, 0.9f, 0.9f);

         glBegin(GL_QUADS);

                 glVertex3f(-100.0f, 0.0f, -100.0f);

                 glVertex3f(-100.0f, 0.0f, 100.0f);

                 glVertex3f( 100.0f, 0.0f, 100.0f);

                 glVertex3f( 100.0f, 0.0f, -100.0f);

         glEnd();

// Draw 36 SnowMen

         for(int i = -3; i < 3; i++)

                 for(int j=-3; j < 3; j++) {

                          glPushMatrix();

                          glTranslatef(i*10.0,0,j * 10.0);

                          glCallList(snowman_display_list);;

                          glPopMatrix();

                 }

         glutSwapBuffers();

}

The following functions are the callback functions of the special key control we registered, and the release of the key (the release of the key ).

void pressKey(int key, int x, int y) {

         switch (key) {

                 case GLUT_KEY_LEFT : 

                          deltaAngle = -0.01f;break;

                 case GLUT_KEY_RIGHT : 

                          deltaAngle = 0.01f;break;

                 case GLUT_KEY_UP : 

                          deltaMove = 1;break;

                 case GLUT_KEY_DOWN : 

                          deltaMove = -1;break;

         }

}

void releaseKey(int key, int x, int y) {

         switch (key) {

                 case GLUT_KEY_LEFT : 

                 case GLUT_KEY_RIGHT : 

                          deltaAngle = 0.0f;break;

                 case GLUT_KEY_UP : 

                 case GLUT_KEY_DOWN : 

                          deltaMove = 0;break;

         }

}

There are three new lines of code in the main function.

The glutignorekeyrepeat function transmits a non-zero value to tell glut not to send the keyborad repeat message. Then, the gluspecialupfunc and glukeyboardupfunc call the registered callback function.

int main(int argc, char **argv)

{

         glutInit(&argc, argv);

         glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);

         glutInitWindowPosition(100,100);

         glutInitWindowSize(640,360);

         glutCreateWindow("SnowMen from 3D-Tech");

         initScene();

         glutIgnoreKeyRepeat(1);

         glutSpecialFunc(pressKey);

         glutSpecialUpFunc(releaseKey);

         glutDisplayFunc(renderScene);

         glutIdleFunc(renderScene);

         glutReshapeFunc(changeSize);

         glutMainLoop();

         return(0);

}

You can download this section of the vc6 ). You can also change the camera settings function.

Http://www.lighthouse3d.com/opengl/glut/index.php? 8)