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Render To Texture

 
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71M



Joined: 21 Jun 2005
Posts: 122
Location: London
PostPosted: Tue Nov 01, 2005 4:43 am    Post subject: Render To Texture Reply with quote
Could somebody please explain to me why the following code doesn't work?
I'm basically trying to get rendering to a texture working, but failing miserably!
The font renderer uses the current GU draw list to store polys in. Is that correct or is there another way to render 2D polygons into the render target?

Any help will be greatly received!

Cheers,
71M

Code:
   static const u32      RENDER_TARGET_WIDTH( 256 );
   static const u32      RENDER_TARGET_HEIGHT( 128 );
   u8 *               p_back_buffer( ( u8 * )sceGuSwapBuffers() );      // Get the address of the back buffer
   u8 * const            p_render_target( ( u8 * )( 2 * 512 * 272 * 4 ) );   // Where we are to render to, 2 x frame buffers @ 32bbp
   u32                  frame( 0 );

   while ( CInput::IsButtonDown( CInput::TRIANGLE ) == false )
   {
      CInput::Process();

      sceGuStart( GU_DIRECT, CGfx::GetDrawList() );

      // Setup render target viewport
      sceGuDrawBufferList( GU_PSM_8888, p_render_target, RENDER_TARGET_WIDTH );
      sceGuOffset( 2048 - ( RENDER_TARGET_WIDTH / 2 ), 2048 - ( RENDER_TARGET_HEIGHT / 2 ) );
      sceGuViewport( 2048, 2048, RENDER_TARGET_WIDTH, RENDER_TARGET_HEIGHT );

      if ( frame == 0 )   sceGuClearColor( 0xff800000 );
      else            sceGuClearColor( 0xff000080 );

      sceGuClear( GU_COLOR_BUFFER_BIT );

      CFont::GetDefaultFont()->Print( "COME ON!", V2( 0.f, 0.f ), 0xff00ff00 );   // Render some text


      // Restore normal viewport and draw buffer
      sceGuDrawBufferList( GU_PSM_8888, p_back_buffer, 512 );
      sceGuOffset( 2048 - ( CGfx::s_ScreenWidth / 2 ), 2048 - ( CGfx::s_ScreenHeight / 2 ) );
      sceGuViewport( 2048, 2048, CGfx::s_ScreenWidth, CGfx::s_ScreenHeight );

      sceGuClearColor( 0xff554433 );
      sceGuClear( GU_COLOR_BUFFER_BIT );

      //
      //   Draw the render target half size on the screen
      //
      vert_list[ 0 ].uv.x = 0.f;
      vert_list[ 0 ].uv.y = 0.f;
      vert_list[ 0 ].color = 0xffffffff;
      vert_list[ 0 ].pos.x = 0.f;
      vert_list[ 0 ].pos.y = 0.f;
      vert_list[ 0 ].pos.z = 0.f;

      vert_list[ 1 ].uv.x = RENDER_TARGET_WIDTH;
      vert_list[ 1 ].uv.y = 0.f;
      vert_list[ 1 ].color = 0xffffffff;
      vert_list[ 1 ].pos.x = 0.f + ( RENDER_TARGET_WIDTH / 2 );
      vert_list[ 1 ].pos.y = 0.f;
      vert_list[ 1 ].pos.z = 0.f;

      vert_list[ 2 ].uv.x = 0.f;
      vert_list[ 2 ].uv.y = RENDER_TARGET_HEIGHT;
      vert_list[ 2 ].color = 0xffffffff;
      vert_list[ 2 ].pos.x = 0.f;
      vert_list[ 2 ].pos.y = 0.f + ( RENDER_TARGET_HEIGHT / 2 );
      vert_list[ 2 ].pos.z = 0.f;

      vert_list[ 3 ].uv.x = RENDER_TARGET_WIDTH;
      vert_list[ 3 ].uv.y = RENDER_TARGET_HEIGHT;
      vert_list[ 3 ].color = 0xffffffff;
      vert_list[ 3 ].pos.x = 0.f + ( RENDER_TARGET_WIDTH / 2 );
      vert_list[ 3 ].pos.y = 0.f + ( RENDER_TARGET_HEIGHT / 2 );
      vert_list[ 3 ].pos.z = 0.f;

      const u8 * const   p_render_target_edram( ( u8 * )( ( u32 )( p_render_target ) + ( u32 )( sceGeEdramGetAddr() ) ) );

      sceGuEnable( GU_TEXTURE_2D );
      sceGuTexFunc( GU_TFX_MODULATE, GU_TCC_RGBA );
      sceGuTexWrap( GU_CLAMP, GU_CLAMP );
      sceGuTexFilter( GU_LINEAR, GU_LINEAR );
      sceGuTexScale( 1.0f, 1.0f );
      sceGuTexOffset( 0.0f, 0.0f );
      sceGuTexMode( GU_PSM_8888, 0, 0, 0 );
      sceGuTexImage( 0, RENDER_TARGET_WIDTH, RENDER_TARGET_HEIGHT, RENDER_TARGET_WIDTH, p_render_target_edram );
      sceGuDrawArray( GU_TRIANGLE_STRIP, GU_TEXTURE_32BITF | GU_COLOR_8888 | GU_VERTEX_32BITF | GU_TRANSFORM_2D, 4, 0, vert_list );

      frame = ( frame ? 0 : 1 );

      sceGuFinish();
      sceGuSync( 0, 0 );

      sceDisplayWaitVblankStart();

      p_back_buffer = ( u8 * )sceGuSwapBuffers();
   }
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71M



Joined: 21 Jun 2005
Posts: 122
Location: London
PostPosted: Tue Nov 01, 2005 4:46 am    Post subject: Reply with quote
Oh, by the way I don't have a Z buffer, hence only 2 frame buffers are currently reside in VRAM.

Code:
u8 * const            p_render_target( ( u8 * )( 2 * 512 * 272 * 4 ) );   // Where we are to render to, 2 x frame buffers @ 32bbp
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Paco



Joined: 09 Oct 2005
Posts: 54
PostPosted: Tue Nov 01, 2005 12:15 pm    Post subject: Reply with quote
71M wrote:
Oh, by the way I don't have a Z buffer, hence only 2 frame buffers are currently reside in VRAM.

The Gu init will set a ZBuffer up for ya, so make sure you explicitly disable Z writes and Z compares. Check the source code code for sceGuDrawBuffer() if you want to see exactly what it does.
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Paco
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71M



Joined: 21 Jun 2005
Posts: 122
Location: London
PostPosted: Tue Nov 01, 2005 6:41 pm    Post subject: Reply with quote
Hi Paco,
Yup, all z/depth tests are disabled after the call to sceGuDrawBuffer().
I tried rendering to the top of VRAM just to make sure, but still the same results.
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71M



Joined: 21 Jun 2005
Posts: 122
Location: London
PostPosted: Wed Nov 02, 2005 6:15 am    Post subject: Reply with quote
Hmm, after further tests, it seems that the alpha component isn't being cleared correctly.
If I upload a texture with alpha set to 255 to the render target address it works fine.
Is there something else that I need to do to clear the alpha bits?
Does this sound correct in anyones experience?

Cheers,
71M
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Paco



Joined: 09 Oct 2005
Posts: 54
PostPosted: Wed Nov 02, 2005 8:55 am    Post subject: Reply with quote
71M wrote:
Hmm, after further tests, it seems that the alpha component isn't being cleared correctly.

Ahh yes you can't use the texture alpha from a rendertarget unless you do some extra work. If I remember correctly, the alpha channel of a rendertarget contains the stencil buffer.
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Paco
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71M



Joined: 21 Jun 2005
Posts: 122
Location: London
PostPosted: Wed Nov 02, 2005 9:01 am    Post subject: Reply with quote
Excellent, thanks for that information. At least it's not me going mad :)
I have done some extra work, and everything seems to be working correctly now.
To see the render to target and the code that appears to be working for me, check out the next release of FileAssistant++ ;)

Cheers,
71M
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