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Microsoft Windows Logo Program System and Device Requirements  —  93

Hardware supports transparent blter. There is no restriction on source size. A transparent blter can perform a block transfer (blt) with a source key transparent color. This requirement assumes that the blter is asynchronous with the host processor.

B4. Hardware provides support to prevent tearing.

Hardware provides support to prevent tearing.  The hardware must support a mechanism for preventing visible artifacts such as tearing. The mechanism for doing this is at the discretion of the hardware designer, but it must support tear-free capabilities for both full-screen and non-occluded windowed applications. Only one of two simultaneous displays of the same image on two displays (for example, internal mobile panel and external VGA monitor attached) must meet this requirement. The mechanism to prevent tearing must be performed in synchronization with the vertical blanking interval (VBI).

Except when explicitly requested to do otherwise by an application (via Microsoft DirectDraw), blts must synchronize with the vertical scan line to avoid tearing. The ability to read the current scan line supports blting or writing to the screen without tearing. In some contexts, such as video playback, this support eliminates the need for the secondary overlay buffer. Other exceptions to this requirement may be allowed and are documented in the Windows DDK.

B4.1.4.8 Adapter supports hardware-accelerated 3-D graphics

Including these additional new 3-D requirements for hardware support:

B4. Multi-texturing.

Multitexturing hardware can apply multiple textures to a polygon. The most common application of multitexturing is with map-based techniques for diffuse lighting and specular reflections.

Implementing this capability requires supporting two or more sets of independent texture coordinates.

The following texture combination operations are required:

MODULATERGB: Component-wise multiplication of both texture colors.

MODULATELPHA: Multiply colors of one texture by the alpha of the other.

ADD: Component-wise addition of both textures.

BLEND: Linear combination of textures weighted by a scalar specified in a register or in a polygon alpha.

Multitexturing is used to compute the texture value that participates in the pixel pipeline implemented in Direct3D.

This technique must work in combination with fogging and alpha blending, but is not required to operate at the same time as other advanced filtering. Multipass multitexturing is acceptable; single-pass multitexturing is preferred.

B4. Source and destination alpha blending; required texture size increases to 1024×1024 for all texture operations.

Hardware supports RGB Rasterization. In red-green-blue (RGB) mode under Microsoft Direct3D, shading across a surface is accomplished by independently interpolating all color components. The following capabilities are required for RGB rasterization:

B4. Textures. These include the following:

MIP–mapped textures

Bilinear, or better filtered textures, rather than point-sampled, with perspective correction

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