Explanation of TorqueOptions?

Andrew Thompson

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Jul 24, 2013, 2:41:47 PM7/24/13

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Hi guys,

Sorry for a cross-post here and the cartoDB support forum, but I only just found the mailing list.

I'm interested in using Torque and have gotten one of my tables to work with the Github pages demo. But I'm trying to figure out what the various options do. In particular, "blendmode" and its various options are baffling me. Resolution I think I get (but what makes this different than "cell size"?), and steps I have a hunch on (number of frames between start date and end date?).

Thanks for any help! Very cool library.

-Andrew

Andrew Hill

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Jul 24, 2013, 3:15:10 PM7/24/13

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Hey Andrew,

We are working right now to cleanup, speedup, and document the Torque library. We should have a much more user-friendly library in the next couple of weeks. Of course, you can watch the changes on the dev branch once we have a solid internet connection :|

If you have a specific question and want to get running on the old library, I'm happy to answer them. Resolution relates to the actual X,Y dimensions that data will collapse to coming from the server and drawing to pixels. Cell size has to do with buffered trim around it (as in the ships example). There are a number of blendmodes, but I'm not sure actually how many are actually useful in Torque, they are

"lighter",

"source-over",

"copy",

"destination-atop",

"destination-in",

"destination-out",

"destination-over",

"source-atop",

"source-in",

"source-out",

"xor"

And deal with how a pixel is drawn giving new information and existing information (already drawn) on the map.

Like I said though, we are trying to clean this up pretty quickly!

Cheers,

Andrew

-Andrew

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Andrew Thompson

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Jul 24, 2013, 4:02:15 PM7/24/13

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Thanks Andrew.

All, I found this paper that uses the same terminology as Torque's available blend modes and provides some extra detail (and helpful graphics of each!): http://dev.w3.org/fxtf/compositing-1/#porterduffcompositingoperators

It seems as if the "destination" is whatever basemap you're using (quoting the paper, "Destination is synonymous with backdrop.") *or* if you have the "cumulative" checkbox checked and you already have points drawn on the map, then destination includes those as well. The "source" seems to be the dots/other symbology drawn by Torque for whatever time-enabled data you have. I don't think this makes much difference if you don't have cumulative checked. If you are displaying cumulative results though, it seems to differ a lot.

Currently I'm a fan of "source-over": it seems to give more emphasis to newly-drawn points. When drawing a point on top of an area where an old point was drawn (ie, in the example, an old weather ship crossing over a route already taken by a historical ship), it makes the intersection a deeper color.

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