rotating object

[GClements]

so how do I adjust the angle variable.

Have keys for "rotate right" and "rotate left". Pressing one causes the angle to increase at a fixed rate, pressing the other causes it to decrease at a fixed rate.

[pbivens]

here is the code I am using

void ship_left_two()
{
       angle+=2.5f;
}
 
void ship_right_two()
{
	angle-=2.5f;
}

here is the drawing code

void DrawShip(GLfloat position_X,GLfloat position_Y, GLfloat position_Z, GLfloat rotation,GLfloat color)
{
	glPushMatrix();
	double magnitude = sqrt(position_X * position_X + position_Y * position_Y);
	double angle = atan2(position_Y,position_X);
	position_X = magnitude * cos(angle);
	position_Y = magnitude * sin(angle);
//	double acceleration = sqrt(position_X * position_X + position_Y * position_Y);
//	double angle = atan2(position_Y,position_X);
//	position_X = acceleration * cos(angle);
//	position_Y = acceleration * sin(angle);
//	position_X = speed_X;
//	position_Y = speed_Y;
//	glRotatef(rotation,0.0f,0.0f,1.0f);
	glTranslatef(position_X, position_Y, position_Z);
	glColor3f(color,0.0f,0.0f);
	glBegin(GL_LINE_LOOP);
	glVertex3f(0.0f,-0.25f,0.0f);
	glVertex3f(-0.25f,-0.5f,0.0f);
	glVertex3f(-0.5f,-0.5f,0.0f);
	glVertex3f(0.0f,0.5f,0.0f);
	glVertex3f(0.5f,-0.5f,0.0f);
	glVertex3f(0.25f,-0.5f,0.0f);
	glVertex3f(0.0f,-0.25f,0.0f);
	glEnd();
	glPopMatrix();
}

I am still a little confused

[GClements]

here is the drawing code

	double magnitude = sqrt(position_X * position_X + position_Y * position_Y);
	double angle = atan2(position_Y,position_X);
	position_X = magnitude * cos(angle);
	position_Y = magnitude * sin(angle);

This doesn't belong here. The drawing code in your first post was fine.

The issue is how you obtain the position which you pass to the drawing function.

[pbivens]

now I am totally confused, please help