Float pbuffer

OpenGL OpenGL: Advanced Coding
1

Hi,
i’ve realized a simple class to manage pbuffer and all functions correctly, now i’d like to add support for float pbuffer, after a seach on web i’ve found nothing of interesting, someone knows links where to learn?
To use float pbuffer i’ve to use special extensions, different from ati to nvidia, or does exist common extensions? and which card does support it?
Thank you

2

Before calling the chooseFormat routine, add these attributes

  if(pBufferFormat & PBUFFER_FORMAT_FLOAT)
  {
    attributes[i++] = WGL_PIXEL_TYPE_ARB;
    if(GLEE_NV_float_buffer)
    {
      attributes[i++] = WGL_TYPE_RGBA_ARB;
      attributes[i++] = WGL_FLOAT_COMPONENTS_NV;
      attributes[i++] = GL_TRUE;
    }
    else
    {
      if(GLEE_WGL_ATI_pixel_format_float)
        attributes[i++] = WGL_TYPE_RGBA_FLOAT_ATI;
      else
        attributes[i++] = WGL_TYPE_RGBA_ARB;
    }
  }
3

i’ve tried in this way:
i have an application that use a pbuffer (8 bit for 4 component) to build a texture and use it on a cube. All works fine.
Now i’ve simply added this line to use float pbuffer and changed color bit to 32:

  
int attrList[] =
{
 WGL_SUPPORT_OPENGL_ARB, true,
 WGL_DRAW_TO_PBUFFER_ARB, true,
 WGL_RED_BITS_ARB, 32,
 WGL_GREEN_BITS_ARB, 32,
 WGL_BLUE_BITS_ARB, 32,
 WGL_ALPHA_BITS_ARB, 32,
 WGL_DEPTH_BITS_ARB, 24,
 WGL_DOUBLE_BUFFER_ARB, false,
 WGL_PIXEL_TYPE_ARB,WGL_TYPE_RGBA_FLOAT_ATI,
 0
};
.......
if(!wglChoosePixelFormatARB(tempCurrenthDC, attrList, NULL, 1,&pixelFormat, &numFormats));
.......
........

It gives me not errors but framerate now is under 1 fps, is this correct?
(i have a radeon 9700)

4

try to disable blending and alpha testing.
seems you ran into a software emulated state configuration.

5

Thank you,i’ve forgotten to disable alpha test and blending, now it’s ok…

6

Why do you have to disable alpha test and blending?

7

if i don’t disable alpha testing (blending is not necessary), framerate goes down 1 fps (maybe opengl switch to software mode)…

8

Originally posted by YengaMatic:
Why do you have to disable alpha test and blending?
The hardware doesn’t support blending on floating point textures.