Summed Area Table Filter

[AnastaZIuk]

Status:

• written and tested OUTDATED, changed many times

almost done

[AnastaZIuk]

done

[AnastaZIuk]

I will do exactly what I did before but with no caching nor wasting memory for all the layers

[Crisspl]

Don't use auto this much! It becomes illegible, use auto only in generic/template code when you actually need it and in case of very long type names (but even then prefer typedef/using instead). auto i = 0u isnt a good place to use auto for sure!

[Crisspl]

Actually... i dont know why you even touch output regions while decoding.. Just do CBasicImageFilterCommon::executePerRegion(commonExecuteData.inImg, decode, commonExecuteData.inRegions.begin(), commonExecuteData.inRegions.end(), clip);, fill scratch with decoded texels, do SAT on scratch, and finally executePerRegion over output regions (encode). Ofc all of the above should be done per layer. Take into account my today's review. Yout negative offsets problem must be result of wrong API usage (of which is great amount as I already found quite a few in review comments), but theres no point in looking for whats wrong because it can be redesigned and done in much simpler way (the main part, (i.e. SAT code) most likely doesnt need any changes)

[devshgraphicsprogramming]

Don't use auto this much! It becomes illegible, use auto only in generic/template code when you actually need it and in case of very long type names (but even then prefer typedef/using instead). auto i = 0u isnt a good place to use auto for sure!

Also auto without a reference (auto&) turns into a "copy-by-value" which has other performance implications.

[devshgraphicsprogramming]

OK I think clip_functor_t needs an explainer https://github.com/buildaworldnet/IrrlichtBAW/blob/shader_pipeline/include/irr/asset/filters/CBasicImageFilterCommon.h#L58

You create the object by giving it the subresource (mip level and layer) of the original image, as well as the offset + extent to clip to, these are pretty much derived from your Filter's State.

you also pass it some texel-block-format info, but thats just for convenience and speed (it can derive those from the format).

Whenever you call the clip functor's function operator https://github.com/buildaworldnet/IrrlichtBAW/blob/shader_pipeline/include/irr/asset/filters/CBasicImageFilterCommon.h#L69 it will produce a newRegion that is the intersection of the offset and extent of the functor and the offset and extent of referenceRegion.

Now in order to produce such a region so its valid and is "as-if" it specified the image itself, you need to do the following:

1. Resolve your bufferWidth if it was 0/-1 and similar because you need to know the byte-distance between successive rows and layers in a clipped region
2. Find an Offset that is both within the functor's state and the referenceRegion (maximum of the coordinates)
3. Find an Extent that when added to the previously computed offsets is still within both rectangles (minimum of the coordinates with the maximum subtracted). targetLimit is the the one-past the max coordinate of the rectangle given in the constructor, while resultLimit is the equivalent for the input region.
4. Compute a new bufferOffset given the change in the offset (offset can only become larger than the reference region so the bufferOffset shall be increased by a non-negative number)

You can see step 2 and 3 being done starting on this line: https://github.com/buildaworldnet/IrrlichtBAW/blob/shader_pipeline/include/irr/asset/filters/CBasicImageFilterCommon.h#L82

If the two rectangles don't intersect (no common texels) then we return false https://github.com/buildaworldnet/IrrlichtBAW/blob/shader_pipeline/include/irr/asset/filters/CBasicImageFilterCommon.h#L84

The offsetInOffset cannot be negative: https://github.com/buildaworldnet/IrrlichtBAW/blob/shader_pipeline/include/irr/asset/filters/CBasicImageFilterCommon.h#L90