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This thread is locked; no one can reply to it.
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| [A5] Drawing primitives to sub-bitmaps causes erroneous behavior |
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X-G
Member #856
December 2000
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The scenario, pseudo-like: set_target_bitmap(create_sub_bitmap(somebitmap)) draw_some_stuff() draw_filled_rectangle() draw_some_more_stuff() When I do this, everything in the same frame after the primitive is drawn as if the sub-bitmap originated at (0, 0) rather than wherever it originates. In other words, half the stuff or so on screen ends up massively offset. xofs and yofs in the ALLEGRO_BITMAP structure are still correct, however. It does appear to draw to the correct parent bitmap (i.e. somebitmap). If I remove the call to draw_filled_rectangle(), everything works correctly, so this surely cannot be an issue in my code. Suggestions? APPEND: Surrounding the primitive draw call with al_store_state(&st, ALLEGRO_STATE_TRANSFORM); causes the error to disappear, so the primitive rendering is apparently doing something inappropriate to the transforms. -- |
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Matthew Leverton
Supreme Loser
January 1999
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Sounds like a bad bug... Is there any primitive specifically that triggers the behavior? Edit: I'm unable to reproduce it using a small test program on Windows with D3D or OpenGL. What types of bitmaps are you working with? Backbuffer, memory, etc. |
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SiegeLord
Member #7,827
October 2006
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I'm having trouble reproducing it as well. Here's the test code I used: 1#include <allegro5/allegro5.h>
2#include <allegro5/allegro_direct3d.h>
3#include <allegro5/allegro_opengl.h>
4#include <allegro5/allegro_primitives.h>
5
6int main()
7{
8 al_init();
9 al_init_primitives_addon();
10 al_install_keyboard();
11
12 al_set_new_display_flags(ALLEGRO_DIRECT3D);
13
14 ALLEGRO_DISPLAY *disp = al_create_display(800, 600);
15 ALLEGRO_BITMAP* bmp = al_create_bitmap(800, 600);
16 ALLEGRO_BITMAP* sub_bmp = al_create_sub_bitmap(bmp, 100, 100, 100, 100);
17 ALLEGRO_BITMAP* square = al_create_bitmap(50, 50);
18
19 al_set_target_bitmap(square);
20 al_clear_to_color(al_map_rgb_f(0, 0, 1));
21 al_set_target_bitmap(al_get_backbuffer(disp));
22
23 ALLEGRO_KEYBOARD_STATE state;
24 while(!al_key_down(&state, ALLEGRO_KEY_ESCAPE))
25 {
26 al_get_keyboard_state( &state );
27
28 /* Clear large bitmap */
29 al_set_target_bitmap(bmp);
30 al_clear_to_color(al_map_rgb_f(0, 0, 0));
31
32 /* Draw to sub-bitmap */
33 al_set_target_bitmap(sub_bmp);
34 /* Primitives call */
35 al_draw_filled_rectangle(0, 0, 50, 50, al_map_rgb_f(1, 0, 0));
36 /* This call should be drawn in different spot than the above one */
37 al_draw_bitmap(square, 0, 0, 0);
38
39 al_set_target_bitmap(al_get_backbuffer(disp));
40 al_draw_bitmap(bmp, 0, 0, 0);
41
42 al_flip_display();
43 }
44
45 return 0;
46}
"For in much wisdom is much grief: and he that increases knowledge increases sorrow."-Ecclesiastes 1:18 |
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X-G
Member #856
December 2000
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Aside from the backbuffer provided by Allegro, I have a separate bitmap that is 1/4 the size of the backbuffer (256x240 vs. 512x480). I then have a sub-bitmap inside this second bitmap, which is 256x244 and offset by 8 on the y-axis. I don't know if it matters, but there is then a clipping rectangle in place on top of this, but in this case it equals the size of the 256x244 sub-bitmap. Then I draw some bitmaps, then the filled rectangle, then some more bitmaps. Finally the larger bitmap is draw_scaled to the real backbuffer. Then I flip. The second batch of bitmaps is drawn 8 pixels above the first. The exact distance changes if I change where the sub-bitmap starts, along both the X and Y axes. I only tried with filled and stroked rectangles, but it happens for both of those. -- |
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Matthew Leverton
Supreme Loser
January 1999
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X-G said: I then have a sub-bitmap inside this second bitmap, which is 256x244 I assume you mean 256x224. But still I cannot duplicate your behavior. However, it looks like OpenGL totally ignores the clipping on a sub bitmap. Using the D3D driver, I get results I expect when clipping a sub bitmap. On OpenGL, it's as if the clipping rectangle was never set. Update: The patch here might help, if this was somehow related to the clipping not being set. |
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X-G
Member #856
December 2000
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Yes, I meant 256x224. I forgot to check last night, but I don't think this is a clipping issue. The bitmaps are literally offset, not inappropriately clipped. I don't know if I'm using the OpenGL driver; whatever is the default on Windows 7. I'll try and cook up a smaller reproduction sample... -- |
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Matthew Leverton
Supreme Loser
January 1999
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If it's particular to D3D or OpenGL you can easily find out: #include <allegro5/allegro_direct3d.h> #include <allegro5/allegro_opengl.h> al_set_new_display_flags(ALLEGRO_OPENGL); // al_set_new_display_flags(ALLEGRO_DIRECT3D);
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