PDA

View Full Version : No 16 Bit mode on Geforce 4 ?



Jan
09-30-2003, 12:50 PM
Hi

I use this pixeldescriptor:

static PIXELFORMATDESCRIPTOR pfd=
{
sizeof (PIXELFORMATDESCRIPTOR),
1,PFD_DRAW_TO_WINDOW|
PFD_SUPPORT_OPENGL|
PFD_DOUBLEBUFFER|
PFD_SWAP_EXCHANGE,
PFD_TYPE_RGBA,
m_iColorDepth,m_iColorDepth/4,0,m_iColorDepth/4,0,m_iColorDepth/4,0,
m_iColorDepth/4,0,0,
0,0,0,0,
m_iDepthBits,m_iStencilBits,0,
PFD_MAIN_PLANE,
0,0,0,0
};

m_iDepthBits is set to 24
m_iStencilBits is set to 8

If i set m_iColorDepth to 32, it works fine.
If i set it to 16, i get the Microsoft renderer and my program crashes (but that could be something else).

Do Geforces (with 45.25 drivers) only support 32 Bit framebuffers?

If i remember correctly i once used a 16 Bit buffer, but that only worked without an alpha-channel. Since i request an alpha-channel, it does not work.

Is this normal?

Jan.

harsman
09-30-2003, 01:48 PM
You won't get 16bit colour if you need destination alpha and/or stencil IIRC. With 24-bit colour and z you get nice 32bit alignment with alpha and z/stencil, which the memory controller probably likes.

Jan
10-01-2003, 09:05 AM
So if i really want 16 Bit color, what other settings do i have to use then?

16 Bit color and 16 Bit Z and no stencil?

Is there any combination with alpha + stencil other than 32 Bit color / 24 depth / 8 stencil?

Jan.

V-man
10-01-2003, 09:41 AM
Jan, enumerate the pixel formats and choose one.

Take a look at ARB_pixel_format

Mazy
10-01-2003, 11:01 AM
i just must ask.. why do you need 16bit? most people aim for better quality all the time http://www.opengl.org/discussion_boards/ubb/smile.gif

Jan
10-01-2003, 11:20 AM
Of course i want good quality. But only if the pc is fast enough. IsnŽt that why people use a 16 Bit color-buffer? Because their pc is not good enough? I just want another option to reduce the quality but to increase the speed. And in a fillrate-limited situation the color-depth can make a big difference.

V-man: IŽll do that, good idea.

Jan.

Jan
10-01-2003, 11:39 AM
I downloaded nVidias "NV Pixel Format 1.0".

It says, that my Gf 4 supports only 2 16 Bit Color formats with alpha. However, those 2 formats use 16 Bit for RGB, but additionally 8 Bit for alpha. Plus, they are only for rendering to bitmaps (not to a window) and they are only rendered by software, so no hw acceleration.

Seems as if here is no 16 Bit color mode with alpha.

Jan.