PRB: Texture Transparency in Direct3D Immediate Mode

The information in this article applies to:

• Microsoft DirectX 3 Software Development Kit, version 3.0 on the following platform: Win95

SYMPTOMS

One method for achieving transparency in textures for use in Direct3D Immediate Mode is to use DirectDraw's support for color keys. When calling IDirectDrawSurface2::SetColorKey() on a texture surface to specify a transparent color, the texture does not exhibit any transparent pixels.

CAUSE

The default values of the internal-state variables in the rendering engine for the rendering module are not set to enable alpha blending so the texture is drawn completely with no transparency.

RESOLUTION

Enable alpha blending by setting the D3DRENDERSTATE_BLENDENABLE render state to TRUE.

MORE INFORMATION

The D3DOP_STATERENDER opcode for the Direct3D execute buffer sets the value of internal-state variables in the rendering engine for the rendering module. The D3DRENDERSTATE_BLENDENABLE D3DRENDERSTATETYPE for this opcode should be set to TRUE to enable alpha blending. The default value is FALSE. Setting this value to TRUE will enable texture transparency.