• Create Account

Banner advertising on our site currently available from just \$5!

### #ActualSillyCow

Posted 28 September 2013 - 11:27 PM

Switch the order of your rotate and translate.

When you want to rotate an object on it's axis, rotation should come first.

However, since openGL transforms are a stack, what happens first is what is closest to the code.

So the order of transforms of opengl is actually resversed.

This is kind of confusing at first, but is really logical when you need heirerchial animations (like a skeleton). It's also required because of the linear-algebra behind openGL.

So what you should be doing is:

void DrawShip(GLfloat position_X,GLfloat position_Y, GLfloat position_Z, GLfloat rotation,GLfloat color)
{
glPushMatrix();
glColor3f(color,0.0f,0.0f);
glTranslatef(position_X,position_Y,position_Z); //move only after the ship is rotated.
glRotatef(rotation,0.0f,0.0f,1.0f); //Now rotation will happen before movement
glBegin(GL_LINE_LOOP);glVertex3f(0.0f,-0.25f+position_Y,0.0f); glVertex3f(-0.25f,-0.5f+position_Y,0.0f); glVertex3f(-0.5f,-0.5f+position_Y,0.0f); glVertex3f(-0.0f,0.5f+position_Y,0.0f);
glVertex3f(0.5f,-0.5f+position_Y,0.0f);
glVertex3f(0.25f,-0.5f+position_Y,0.0f);
glVertex3f(0.0f,-0.25f+position_Y,0.0f);
glEnd();
glPopMatrix();
}

### #2SillyCow

Posted 28 September 2013 - 11:26 PM

Switch the order of your rotate and translate.

When you want to rotate an object on it's axis, rotation should come first.

However, since openGL transforms are a stack, what happens first is what is closest to the code.

So the order of transforms of opengl is actually resversed.

This is kind of confusing at first, but is really logical when you need heirerchial animations (like a skeleton). It's also required because of the linear-algebra behind openGL.

So what you should be doing is:

void DrawShip(GLfloat position_X,GLfloat position_Y, GLfloat position_Z, GLfloat rotation,GLfloat color)
{
glPushMatrix();
glColor3f(color,0.0f,0.0f);
glTranslatef(position_X,position_Y,position_Z); //move only after the ship is rotated.
glRotatef(rotation,0.0f,0.0f,1.0f); //Now rotation will happen before movement
glBegin(GL_LINE_LOOP);glVertex3f(0.0f,-0.25f+position_Y,0.0f); glVertex3f(-0.25f,-0.5f+position_Y,0.0f); glVertex3f(-0.5f,-0.5f+position_Y,0.0f); glVertex3f(-0.0f,0.5f+position_Y,0.0f); glVertex3f(0.5f,-0.5f+position_Y,0.0f); glVertex3f(0.25f,-0.5f+position_Y,0.0f); glVertex3f(0.0f,-0.25f+position_Y,0.0f); glEnd(); glPopMatrix(); }

### #1SillyCow

Posted 28 September 2013 - 11:26 PM

Switch the order of your rotate and translate.

When you want to rotate an object on it's axis, rotation should come first.

However, since openGL transforms are a stack, what happens first is what is closest to the code.

So the order of transforms of opengl is actually resversed.

This is kind of confusing at first, but is really logical when you need heirerchial animations (like a skeleton). It's also required because of the linear-algebra behind openGL.

So what you should be doing is:

void DrawShip(GLfloat position_X,GLfloat position_Y, GLfloat position_Z, GLfloat rotation,GLfloat color)
{
glPushMatrix();
glColor3f(color,0.0f,0.0f);
glTranslatef(position_X,position_Y,position_Z); //move only after the ship is rotated.
glRotatef(rotation,0.0f,0.0f,1.0f); //Now rotation will happen before movement

glBegin(GL_LINE_LOOP);

glVertex3f(0.0f,-0.25f+position_Y,0.0f); glVertex3f(-0.25f,-0.5f+position_Y,0.0f); glVertex3f(-0.5f,-0.5f+position_Y,0.0f); glVertex3f(-0.0f,0.5f+position_Y,0.0f); glVertex3f(0.5f,-0.5f+position_Y,0.0f); glVertex3f(0.25f,-0.5f+position_Y,0.0f); glVertex3f(0.0f,-0.25f+position_Y,0.0f); glEnd(); glPopMatrix(); }

PARTNERS