Table of contents
Collapse the table of content
Expand the table of content

Promoting Z Buffers to 32 Bits Per Pixel

Last Updated: 2/14/2017

This topic applies to DirectX 8.0 and later.

A display driver whose display device does not support rendering to z and color buffers with differing pixel depths must transparently promote a 16 bits per pixel (bpp) z buffer to 32 bpp in order to render both the z buffer and a 32 bpp color buffer at the same time. Note, however, that the z buffer cannot also have stencil bits. Therefore, applications are not required to correct this mismatch in buffer pixel depth.

If the driver's display device can render to z and color buffers of differing pixel depth, the driver sets the D3DFORMAT_OP_ZSTENCIL_WITH_ARBITRARY_COLOR_DEPTH flag in the dwOperations member of the DDPIXELFORMAT structure for z-buffer formats. The Direct3D runtime then lets applications render to any mismatch of z- and color-pixel depths.

If the driver does not set D3DFORMAT_OP_ZSTENCIL_WITH_ARBITRARY_COLOR_DEPTH for z-buffer formats, the runtime only lets applications render to a mismatch of 32 bpp color buffer and 16 bpp z buffer with no stencil bits as described in the introductory paragraph. In this case, the driver allocates a 32 bpp z buffer in place of the requested 16 bpp z buffer.

If D3DFORMAT_OP_ZSTENCIL_WITH_ARBITRARY_COLOR_DEPTH is not set, the runtime does not let applications render to the following mismatch scenarios:

  • 16 bpp color buffer and 32 bpp z buffer at the same time. For rendering to succeed in this scenario, the driver would have to substitute a 16 bpp z buffer for the 32 bpp z buffer, which would degrade z precision and cause noticeable artifacts.

  • Any z format whose depth stencil does not occupy the same number of bits per pixel as the color buffer (in other words, mismatching z and stencil surfaces). For rendering to succeed in this scenario, the driver would have to change the number of stencil bits, which would also cause noticeable artifacts.

Send comments about this topic to Microsoft

© 2017 Microsoft