how to speed up objects movement speed in opengl without dropping movement smoothness - performance

Question

Here's the function which is registered as display function in glutDisplayFunc()
void RenderFunction(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPointSize(5);
glBegin(GL_POINTS);
glVertex2i(0+i,0);
glEnd();
glutSwapBuffers();
i+=1;
glutPostRedisplay();
}
This way the point moves across the screen but its speed is really slow.
I can speed it up by incrementing i with greater number than 1, but then the motion doesn't seem smooth. How do I achieve higher speed?
I used to work with SFML which is made on the top of OpenGL and there the object moved really fast with move() method. So there has to be a way in OpenGL too.

Answer 1

In this case, there's probably not a lot you can do other than moving your point further each time you redraw. In particular, most performance improvement probably won't have any significant effect on the perceived speed in this case.
The problem is fairly simple: you're changing the location by one pixel at a time. Chances are pretty good that you have screen updating "locked" so it's happening in the conjunction with the monitor's refresh.
Assuming that's the case, with a typical monitor that refreshes at 60 Hz, you're going to get a fixed rate of your point moving 60 pixels per second. If you improve the code's efficiency, the movement speed won't change--it'll just reduce the amount of CPU time you're using to move the dot at the same speed.
Essentially the only choice to move if faster is to move more than one pixel per screen refresh. One pixel per screen refresh means 60 pixels per second, so (for example) to move across a typical HD screen (1920 dots horizontally) will take 1920 pixels/60 pixels/second = 32 seconds.
With really slow code, you might use 1% of the CPU to do that. With faster code, that might drop to some unmeasureably small amount--but either way, it's going to travel the same speed, so it'll take 32 seconds to get across the screen.
If you wanted to, you could unlock your screen updates from the screen refresh. Since you're only drawing one point, you can probably update the screen at a few thousand frames per second, so the dot would appear to move across the screen a lot faster.
In reality, however, the monitor is still only refreshing the screen at 60 Hz. When your code updates faster than that, it just means you'll produce a number of intermediate updates that never show up on the screen. As far as the pictures actually showing up on the screen go, you're just moving the point more than one pixel per screen refresh. The fact that you updated data in memory for all the intermediate points doesn't really change anything. The visible result is essentially the same as if you redrew once per screen refresh, and moved the point a lot further each time.

Answer 2

define model view matrix with i as translation component.
Then apply this matrix to the vertex you are defining. But yes as others are telling try to move to modern OpenGL.
glMatrixMode(GL_MODELVIEW);
glTranslatef(i, i, i);