On May 18, 2009, at 3:34 PM, George Toledo wrote:
When Native Core Image Rendering is enabled it indicates that the filters render directly to the destination context. I understand this, but I don't understand what it is rendering to if it's not rendering to the destination context. I am basically seeking an explanation of "what exactly is happening to impact performance to this extent".
When it is on, we use [ciContext drawImage:], just like you would do in your own code with a fully CI-based render chain. That's why it is fast, the CoreImage framework can do their special optimizations and make it so.
When Direct Rendering is off, we render to an OpenGL quad which means retrieving the CI image data first and then drawing it like we draw all other image types. There are no assumptions made about the image's contents, so there may be conversions. I think ideally there would not be any difference in speed so write bugs if it's unexpectedly slow. The engine expert isn't on these lists so bug are the best way to make sure that gets looked at.
Troy
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