Hi,
I’m a newbie to opengl, trying to write a code,
where i’ve 2 objects circle and a point. as the circle moves, the point traces a curve. when i use a function to move the circle, i’ve to always give
glClear (GL_COLOR_BUFFER_BIT) , which erases the current scene in on the window, and draws the scene completely again. but when i want to trace a curve, with respect to the movement of the circle, i cannot use glClear, as it will erase, the curve, drawn in the previous iteration. how can i avoid this. I want to trace the curve, along with the movement of circle.
Thanks in advance,
Surya
You have to trace your curve again and again everytime as well as the circle, even if the curve does not move.
void render(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
/* render curve here /
glTranslatef(/ circle movement here /);
/ render circe here */
}
And if the curve is very long to render (e.g. millions of vertices) you may render your curve, grab the picture into a texture, and then render a simple quad with that texture over it, to simulate the presence of the curve. It’s a bit complex to setup, though, so you may do it only if you need better performance.