Ho to use multi sampling ?

no-reply@allegro.cc (Soporythmique) — Thu, 06 Sep 2012 05:24:05 +0000

Hello,

(Sorry for my bad english)

I'm having trouble with the multi-sampling, I know that this function il enabled by default, but when I try this:

#SelectExpand
  1al_set_new_display_option(ALLEGRO_SAMPLE_BUFFERS, 1, ALLEGRO_SUGGEST);
  al_set_new_display_option(ALLEGRO_SAMPLES, 8, ALLEGRO_SUGGEST);
  if (al_get_display_option(Affichage, ALLEGRO_SAMPLE_BUFFERS))
  {
      printf("With multisampling, level %i\n", al_get_display_option(Affichage, ALLEGRO_SAMPLES));
  }
  else
  {
      printf("Without multisampling.\n");
  }

It return "Without multisampling" . . .
I draw on a bitmap, and then draw that bitmap on the screen like I saw on a tutorial:

#SelectExpand
 1al_set_target_bitmap(Buffer);
 2    al_clear_to_color(al_map_rgb(0, 0, 0));
 3al_draw_line(x1, y1, x2, y2, al_map_rgb(255, 120, 120), 0);
 4    al_set_target_bitmap(al_get_backbuffer(Affichage));
 5    al_draw_scaled_bitmap(Buffer, 0, 0, LargeurAffichage, HauteurAffichage, 0, 0, 1920, 1080, 0);

So I don't know where is the problem . . .

Thanks for your help

PS: My graphic crad is a 520M

no-reply@allegro.cc (Trent Gamblin) — Thu, 06 Sep 2012 05:27:35 +0000

1) I think you have to be drawing onto the display for multisampling to work (but I could be wrong!)

2) According to your code you're setting those display options (SAMPLE_BUFFERS, SAMPLES) after you already have a display. You have to set the before you create a display.

no-reply@allegro.cc (Soporythmique) — Thu, 06 Sep 2012 05:51:38 +0000

Trent Gamblin said:

According to your code you're setting those display options (SAMPLE_BUFFERS, SAMPLES) after you already have a display. You have to set the before you create a display.

Thank you it was just that, I thought it was activated by default.

Just a last question, I didn't understound the utility of drawing on a bitmap for then draw this bitmap on the screen . . . it use twice more time no ?

Currently I draw directly on the screen, and it work perfectly.

no-reply@allegro.cc (Elias) — Thu, 06 Sep 2012 05:51:47 +0000

Multisampling only works when drawing directly to the display.

(We could add multisampling for offscreen targets if someone needs it and wants to implement it, for example by using this extension: http://www.khronos.org/registry/gles/extensions/EXT/EXT_multisampled_render_to_texture.txt

Either just enabling it for all video bitmaps if the display has multi-sampling or adding a new bitmap flag would work API-wise I think.)

no-reply@allegro.cc (Trent Gamblin) — Thu, 06 Sep 2012 06:09:12 +0000

Enable it with a ~~display~~ bitmap flag out of those two options. Otherwise there's no way to get a non-multisampled bitmap if you have a multi-sampled display. I'm sure there's a use case.