forums.ps2dev.org Forum Index forums.ps2dev.org
Homebrew PS2, PSP & PS3 Development Discussions
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

GU buffers autoswapping?

 
Post new topic   Reply to topic    forums.ps2dev.org Forum Index -> PSP Development
View previous topic :: View next topic  
Author Message
svxs



Joined: 19 Jun 2009
Posts: 15
PostPosted: Mon Jun 29, 2009 11:13 am    Post subject: GU buffers autoswapping? Reply with quote
I had an interesting idea. I need to convert DXTn compressed images to RGBA8 pixel format. The GU can handle DXTn compressed images natively, so my idea was to use it to do the conversion so that I won't need to write an algorithm to do it in software.

I planned on using the GU to render it to the draw buffer and just not swap with the display buffer. I'd have it render the DXTn image as a texture on a quad and read back the RGB data directly from the draw buffer in VRAM to somewhere in RAM without affecting anything currently on the screen.

But the buffers are swapping automatically. My code doesn't contain any calls to sceGuSwapBuffers(), so I have no idea what's up.

I also tried going directly to the rasterizer instead of transforming first, but I was wrong to assume that it was my problem.

Code:

/* Body of the function that's messing up. */
sceGuStart (GU_DIRECT, gList);

sceGumMatrixMode (GU_MODEL);
sceGumLoadIdentity()

draw_quad (64, 64);

sceGuFinish();
sceGuSync (0, 0);

/* To illustrate that nothing is going on after this: */
while ( 1 )
{
}


Code:

void
draw_quad ( const float nW
            , const float nH )
{
  struct vert2d
  {
    float u, v;
    uint32_t color;
    float x, y, z;
  } *p_verts = (struct vert2d *)
               sceGuGetMemory (2 * sizeof (struct vert2d));

  p_verts[0] = (struct vert2d) { 0.0f, 0.0f, 0xFF0000FF, 0.0f, 0.0f, 0.0f };
  p_verts[1] = (struct vert2d) { nW,   nH,   0xFF0000FF, nW,   nH,   0.0f };

  sceGumDrawArray
  (
    GU_SPRITES
    , GU_TEXTURE_32BITF|GU_COLOR_8888|GU_VERTEX_32BITF|GU_TRANSFORM_3D
    , 2
    , 0
    , p_verts
  );
}


Any idea what's causing the buffers to swap? Any idea how to avoid it?
Back to top
View user's profile Send private message
svxs



Joined: 19 Jun 2009
Posts: 15
PostPosted: Tue Jun 30, 2009 4:25 am    Post subject: Reply with quote
Still can't figure this out.

The only things happening prior to this are:

A thread is set up to handle the home button.
The debug screen is initted to display the status of some operations:
The contents of a few archives is indexed in a hash table.
A few megabytes of models and images for textures are stored.
The GU is initted for drawing. Pasting that code into a sample from the SDK doesn't force the sample to automatically swap the buffers, so it isn't that.

And then, the above code is used. I'm puzzled.
Back to top
View user's profile Send private message
J.F.



Joined: 22 Feb 2004
Posts: 2906
PostPosted: Tue Jun 30, 2009 6:14 am    Post subject: Reply with quote
You'll have to post more code if you want more than just guesses.
Back to top
View user's profile Send private message AIM Address
Jim



Joined: 02 Jul 2005
Posts: 487
Location: Sydney
PostPosted: Tue Jun 30, 2009 7:52 am    Post subject: Reply with quote
Are you accidentally drawing on the frontbuffer?

Jim
_________________
http://www.dbfinteractive.com
Back to top
View user's profile Send private message Visit poster's website
svxs



Joined: 19 Jun 2009
Posts: 15
PostPosted: Wed Jul 01, 2009 3:53 am    Post subject: Reply with quote
I have a weird feeling that you're right Jim... I'm not sure why I would've been, but all the symptoms point that way. It's tough to tell since I removed the code in order to focus on something else. With a tremendous project like this, it's too easy to get sidetracked by the small things.

What would cause it to draw to the front buffer instead of the back buffer though? Being as intrinsically unfamiliar as I am with the SDK, my only guess would be that it could be the result of some erroneous code as a callback for buffer swapping. I was using a callback for a while, but it would've been registered much later in the program's flow than when this problem was occurring...

I'll try this idea again in a few days probably. There's still a lot of other tiny things to focus on that seem to be causing problems, but that solution to this one makes sense.
Back to top
View user's profile Send private message
J.F.



Joined: 22 Feb 2004
Posts: 2906
PostPosted: Wed Jul 01, 2009 7:14 am    Post subject: Reply with quote
When you setup the GU, the first few lines usually look like this:

Code:
   sceGuInit();
   sceGuStart(GU_DIRECT, list);
   sceGuDrawBuffer(GU_PSM_8888, (void*)0, BUF_WIDTH);
   sceGuDispBuffer(SCR_WIDTH, SCR_HEIGHT, (void*)0x88000, BUF_WIDTH);


The (void*)0 sets the offset in vram for the draw buffer, and the (void*)0x88000 sets the offset for the display buffer. This would most likely were you'd get them backwards (or possible have them set to the same value).
Back to top
View user's profile Send private message AIM Address
svxs



Joined: 19 Jun 2009
Posts: 15
PostPosted: Thu Jul 02, 2009 4:44 am    Post subject: Reply with quote
Hmm. Definitely wouldn't be that, then. Pointers to all three memory areas for the draw, display, and z buffers have always been to the correct places, although I recently started using valloc() from the libvram helper library to allocate them properly. The pointers are properly converted to VRAM-relative addresses for that, of course.

Was:
Code:

  void *const p_draw_buffer = (void *) 0x0;
  void *const p_display_buffer = (void *) 0x88000;
  void *const p_depth_buffer = (void *) 0x110000;

  /* Set up the buffers. */
  sceGuDrawBuffer (GU_PSM_8888, p_draw_buffer, 512);
  sceGuDispBuffer (SCREEN_WIDTH, SCREEN_HEIGHT, p_display_buffer, 512);
  sceGuDepthBuffer (p_depth_buffer, 512);


Now is:
Code:

  void *const p_draw_buffer = vGuPointer (valloc (512 * SCREEN_HEIGHT * 4));
  void *const p_display_buffer = vGuPointer (valloc (512 * SCREEN_HEIGHT * 4));
  void *const p_depth_buffer = vGuPointer (valloc (512 * SCREEN_HEIGHT * 2));

  /* Set up the buffers. */
  sceGuDrawBuffer (GU_PSM_8888, p_draw_buffer, 512);
  sceGuDispBuffer (SCREEN_WIDTH, SCREEN_HEIGHT, p_display_buffer, 512);
  sceGuDepthBuffer (p_depth_buffer, 512);


It would have to be something else, but my guess is that it was having to do with a callback and some bad code to swap buffers that I wrote in a rush. I removed it a day or two ago since it became no longer necessary; I'll add it back in some time and see if this whole idea goes any differently.

Edit:

On second thought, I wasn't even swapping the buffers at that point. A mystery.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    forums.ps2dev.org Forum Index -> PSP Development All times are GMT + 10 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group