Rotating objects

Put glTranslate before glRotate, for example:

glLoadIdentity();
static int i = 0;

glTranslatef(0,0,-10);
glRotatef(++i,0,1,0);

DisplayModel();

and ensure that DisplayModel() hasn't any glTranslate and the model is centered.

[Edited by - Lord_Vader on February 21, 2007 3:52:18 PM]

The identity matrix resets your rotations.

Try

Loadidentity
pushmatrix
rotate
popmatrix

Thx

But this doesnt help with my rotating problem: it doesnt spin correctly on its y axis, it spins in wide circcle around 1 point

Put glTranslate before glrotate.

I did but it doesnt help

Can you post the whole code?

#include <gl.h>
#include <glut.h>
#include <cstdlib>
float ypos = 0.0,xpos = 0.0,rotate=0.0;
void drawterrain(){
glColor3f(0,256,0);
glBegin(GL_POLYGON);
glVertex3f(0.1,0.9,0.0);
glVertex3f(0.9,0.9,0.0);
glVertex3f(0.9,0.1,0.0);
glVertex3f(0.1,0.1,0.0);
glEnd();
}
void drawobject(){
glColor3f(256,256,0);
glBegin(GL_POLYGON);
glVertex3f(0.4,0.6,0);
glVertex3f(0.6,0.6,0);
glVertex3f(0.6,0.4,0);
glVertex3f(0.4,0.4,0);
glEnd();
glColor3f(256,0,0);
glBegin(GL_POLYGON);
glVertex3f(0.4,0.6,0);
glVertex3f(0.6,0.6,0);
glVertex3f(0.6,0.6,0.1);
glVertex3f(0.4,0.6,0.1);
glEnd();
}
void display()
{
glLoadIdentity();
glClearColor(256,256,256,0);
glClear(GL_COLOR_BUFFER_BIT);
drawterrain();
glPushMatrix();
glTranslatef(xpos,ypos,0.0);
glRotatef(rotate,0.0,0.0,0.0);
drawobject();
glPopMatrix();
glFlush();
}

void init(){
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(0.0,1.0,-0.1,1.0,-1.0,0.0);
GLfloat lightpos[] = {0.5,0.5,-0.2,0.0};
GLfloat lightdir[] = {0,0,1};
GLfloat red[]={256,0,0};
GLfloat blue[]={0,0,256};
GLfloat white[]={256,256,256};
}
void keyboard(unsigned char key, int x,int y)
{
switch(key){
case 'z':
ypos = ypos+0.01;
display();
break;
case 's':
ypos = ypos - 0.01;
display();
break;
case 'q':
xpos =xpos - 0.01;
display();
break;
case 'd':
xpos =xpos + 0.01;
display();
break;
case 'a':
rotate = rotate +1.0;
display();
break;

}
}
int main(int argc, char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGBA);
glutInitWindowSize(800,600);
glutInitWindowPosition(100,100);
glutCreateWindow("Titel");
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
init();
glutMainLoop();
return 0;
}

You didn't rotate on any axis.

void display(){glLoadIdentity();glClearColor(256,256,256,0);glClear(GL_COLOR_BUFFER_BIT);drawterrain();glPushMatrix();glTranslatef(xpos,ypos,0.0);glRotatef(rotate,0.0,0.0,0.0);   // this is the culpritdrawobject();glPopMatrix();glFlush();}

Here's a working one:

What does that pic supposed to mean? My monitor is borked.

What my object does when i use glrotatef

Did you try my code in the post above your the picture?

It was just a mistake while copying it, i wanted to show my brother how glRotatef works, so it didnt help

I had this problem as well I hope what I'm about to tell you will help you...

You have the 3D cartesian system which has 3 axes, now when you spin around the axes, you take the closest vertex to the axe that you want to spin and spin the entire object while using this vertex as the pivot point, as far as I understand it, correct me if I'm wrong... now what you can do is make sure that the object is centered on the (0, 0, 0) point all the time, meaning, move it to the point you want to and then rotate it. Ok I'm not sure I'm clear enough so let's try some code:

float xRot = 0;float yRot = 0;float zRot = 0;// advance x, y, z rot every few milliseconds. . .//-------------------------------------------// Rendering codeglLoadIdentity();glClearColor(.0f, .0f, .5f, 1.0f);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);glPushMatrix();glLoadIdentity();glRotatef(45.0f + xRot, 1.0f,  .0f,  .0f);glRotatef(45.0f + yRot,  .0f, 1.0f,  .0f);glRotatef(45.0f + zRot,  .0f, .0f,  1.0f);glBegin(GL_QUADS);    glVertex3f(-0.5f,  0.5f, -10.0f);    glVertex3f( 0.5f,  0.5f, -10.0f);        glVertex3f( 0.5f, -0.5f, -10.0f);    glVertex3f(-0.5f, -0.5f, -10.0f);    glEnd();glPopMatrix();

My perspective is:
gluPerspective(45.f, (GLfloat)640/ (GLfloat)480, 1.f, 400.f);

So the basic idea is to keep the object centered on the axes...

Hope that helped...