Ultimately, objects are always drawn in the screen by setting pixels into it. Plotting a point by setting a pixel is entirely reasonable, and can be indeed done directly, in realtime, for several millions of points. I just tested the C program below, compiled with gcc without optimizations, and it gives about 80 fps for three million points (on my 6 year-old thinkpad). My point: CPUs are ridiculously fast, and you can indeed do a lot of large-scale data visualization without need to meddle with the GPU.
#define FPS 80
void plot_points(
float *o, // output raster array (w*h)
int w, // width of raster
int h, // height of raster
float *x, // input point coordinates (2*n)
int n // number of input points
)
{
// initialize the output raster
for (int i = 0; i < 2*w*h; i++)
o[i] = 0;
// accumulate the points that fall inside the raster
for (int i = 0; i < n; i++)
{
int p = x[2*i+0];
int q = x[2*i+1];
if (p >= 0 && p < w && q >= 0 && q < h)
o[w*q+p] += 1;
}
}
#include <stdlib.h>
int main(void)
{
int w = 1000;
int h = 1000;
int n = 3000000;
float *x = malloc(2*n*sizeof*x);
float *o = malloc(w*h*sizeof*o);
for (int i = 0; i < 2*n; i++)
x[i] = 1000*(rand()/(1.0+RAND_MAX));
for (int i = 0; i < FPS ; i++)
plot_points(o, w, h, x, n);
return 0;
}
// NOTE: if this program runs in less than 1 second, it means that it
// is faster than "FPS"
You're plotting individual points here, not a proper data graph. Even if you need a cloud of points, it's not enough, since you need to have different sizes and types of points that may have different sizes based on another data column, and definitely need to be drawn with antialiasing, even if they're simple squares.
Then, to draw something like this imgur.com/a/mXvEBzl (ADS-B data, ~10 million points iirc), you need to connect points with (antialiased) lines, where individual pixel should be blended into plot with respect of line opacity. Also, lines can be of different thickness, so it multiplies your `o[w x p+p] += 1` again.
I'm not even talking about multiple layers that are quite standard.
I use my own plotting app, it takes a lot more than just slap a bunch of points into "float *o". Try to write your own, you will figure it out pretty quickly, unless you're ok with black blobs that resemble the input data.
