Class EXTTextureCompressionDXT1
Support of EXT_texture_compression_s3tc is attractive for OpenGL-ES implementations because it provides compressed textures that allow for significantly reduced texture storage. Reducing texture storage is advantageous because of the smaller memory capacity of many embedded systems compared to desktop systems. Smaller textures also provide a welcome performance advantage since embedded platforms typically provide less performance than desktop systems. S3TC compressed textures are widely supported and used by applications. The DXT1 format is used in the vast majority of cases in which S3TC compressed textures are used.
However, EXT_texture_compression_s3tc specifies functionality that is burdensome for an OpenGL-ES implementation. In particular it requires that the
driver provide the capability to compress textures into S3TC texture formats, as an S3TC texture format is accepted as the internalformat
parameter of TexImage2D and CopyTexImage2D. Further, EXT_texture_compression_s3tc may require conversion from one S3TC format to another during
CompressedTexSubImage2D if the format
parameter does not match the internalformat
of the texture image previously created by
TexImage2D.
In an OpenGL-ES implementation it is therefore advantageous to support a limited subset of EXT_texture_compression_s3tc: Restrict supported texture formats to DXT1 and restrict supported operations to those that do not require texture compression into an S3TC texture format or decompression from an S3TC texture format.
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Field Summary
Modifier and TypeFieldDescriptionstatic final int
Accepted by theinternalformat
parameter of CompressedTexImage2D and theformat
parameter of CompressedTexSubImage2D.static final int
Accepted by theinternalformat
parameter of CompressedTexImage2D and theformat
parameter of CompressedTexSubImage2D. -
Method Summary
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Field Details
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GL_COMPRESSED_RGB_S3TC_DXT1_EXT
public static final int GL_COMPRESSED_RGB_S3TC_DXT1_EXTAccepted by theinternalformat
parameter of CompressedTexImage2D and theformat
parameter of CompressedTexSubImage2D.- See Also:
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GL_COMPRESSED_RGBA_S3TC_DXT1_EXT
public static final int GL_COMPRESSED_RGBA_S3TC_DXT1_EXTAccepted by theinternalformat
parameter of CompressedTexImage2D and theformat
parameter of CompressedTexSubImage2D.- See Also:
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