Specifically, with all the possible time interpolation techniques (explicit/implicit, fixed/adaptive. Which only makes the effort more enormous-looking. As for 4-D grids, I am not convinced that a unique (or even canonical) 4D representation and extent exist. I am not trying to be choosy about whether that's done at the pipeline level. To me, that means the programming model should make multiple time steps available. For example: temporal plots, temporal interpolation, temporal derivative estimation, and streakline generation. My point is that on many occasions, values for multiple timesteps will be required simultaneously for processing. Martink 13:11, (EDT) I agree that both the single-timestep and multi-timestep pipelines have to retrieve all of the data requested in the end. Maybe there is some other approach that makes more sense. That is the same basic situation as not using multiblock just depth first (100 blocks on filter 1, 100 block on filter 2) versus breadth first. requesting one cell for 100 time steps will result in a 100 block data set (a block is really a dataset as well) and for almost all filters the pipeline will iterate them 100 times, once for each block. The multiblock approach I don't think buys us much as the pipeline will just iterate over the blocks all the same. But maybe that is the direction we should head. Well I hear you :) The ideal fix is to go to a true 4D representation and extent. That's just asking for lots of code replication and tedious programming. Also, I suspect that many filters that operate on temporal data will end up creating a multiblock dataset or some equivalent in order to hold the datasets they require. The new executive in VTK 5 is slower than the old one and running the executive once for each frame in an interactive session(15+ fps) doesn't seem terribly feasible. I have two problems with the second approach: user interactivity and developer ease-of-use. My suggestion is to go with the second approach. The second approach is simpler in that it can work with minor changes to the current pipeline. It would tend to use a larger memory footprint (many timesteps in memory at once). The first approach would require changes to the multiblock executive. The second approach is to only fullfill requests for one time step at a a time. The first is that a request for multiple time steps is handled by returning a multiblock dataset, one block for each time step. First finalize buyin on the basic approach.
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