Corbin Simpson schrieb:
> On Mon, Mar 29, 2010 at 5:50 PM, Ian Romanick <i...@freedesktop.org> wrote:
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>>
>> Philipp Klaus Krause wrote:
>>
>>> Well, there is TexSubImage2D. Assuming we have a compressed texture
>>> stored internally as some S3TC format and then the application replaces
>>> part of it using TexSubImage2D. According to ARB_texture_compression we
>>> may not go to uncompressed ("the allocation and chosen compressed image
>>> format must not be a function of any other state and cannot be changed
>>> once they are established". And while ARB_texture_compression does not
>>> require TexSubImage2D support, EXT_texture_compression_s3tc does.
>> Ah. Good catch. My best guess is that there are few, if any, apps that
>> do that. Such apps would be easy to detect. We could enable the
>> non-conformant behavior by default, and provide a driconf switch to
>> disable it. We'd then need to blacklist apps that use unsupported
>> cases. Since we can detect these cases, we can log a message when the
>> occur.
>>
>> Does that seem like a reasonable compromise?
>
> We don't have to compromise at all. If the image is already compressed
> internally, then updating it with TexSubImage or CompressedTexSubImage
> must be done along the block boundaries,
Yes.
> and must be done with
> pre-compressed blocks,
Why?
> so we are never decompressing and recompressing
> the texture.
Philipp
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