Capture SOP

From TouchDesigner 088 Wiki

Summary

The Capture SOP is used to weight points in a geometry to capture regions. The weighting scheme is described in the next section, Capture Region SOP.

The weights and the regions they correspond to are transferred down the SOP chain as point and detail attributes.

The Capture SOP can take an optional second input to specify extra capture regions to use in the capture process. Any capture regions that are in this second input are processed after the capture regions that are in the object hierarchy specified by the Hierarchy parameter. You can also specify a second input and not specify a Parent Object at all.

PythonIcon.png captureSOP_Class

Parameters - Capture Page

Hierarchy - An object hierarchy is traversed to find the Capture Regions with which to do the weighting. This parameter specifies the top of the traversal hierarchy.

Weight From

  • Surface - (default) uses the surface to compute the weight of a point (or CV in the case of NURBS). This is very helpful for NURBS surfaces when the CV's may be far off the surface. By using Weight From Surface, each CV is weight based on the surface's location within a Capture Region. This is determined by calculating the CVs "most influenced point" on the NURBS surface and computing the weight of that position.
  • Points - Using the Weight From Points choice, the location of the point within the region is used for the weighting.

Capture Frame - Specifies the frame number to do the capture computations. Every time TouchDesigner reaches this frame, the geometry will be re-captured. It is a common practice to set the Capture Frame to an frame outside of your animation range, -1 for example.

Note: When a .toe file is loaded, all of the associated capture regions are evaluated at the Capture Frame. Keyframes must be set to position the capture regions properly at the Capture Frame, otherwise the geometry will be weighted incorrectly upon the subsequent file loads.

Point Coloring - This option colors each point by capture region (using point attributes) according to its capture weight. The points inherit their colors from the Capture Region(s) in which they lie. For example, if a point falls within a blue capture region and also a yellow capture region, the point will be colored green (more blue near if the blue weighting dominates, and more yellow if the yellow weight dominates). In addition, the points become darker as the weighting gets lighter. For example, near the edge of a blue region, a caught point will appear dark blue. Near the centre, it will appear bright blue. If a point is not caught by any region, it is colored bright red.

Parameters - Override Page

Override File - The name of the capture override file (*.ocapt). This file is loaded after TouchDesigner completes its point weighting. Each line of the override file lists a point number, a region (path and primitive number) and a weight. The points on the geometry are modified to use these custom weights.

Override File Format - Each line in the override file must have the following format:

For example:

0 /obj/chain_bone1/cregion 0 0.0 
0 /obj/chain_bone2/cregion 0 3.757989 
0 /obj/chain_bone3/cregion 0 1.757989


This weights point 0 to three regions (actually only two because the first entry has a weight of zero). Remember that the Override File is read after TouchDesigner does it's own capture weight computation, so in this case, if point 0 was originally assigned to region /obj/chain_bone4/cregion 0, this part of its weighting would be unchanged. There is no upper limit to the number of regions that can be weighted to a point. If a point/region combination is in the file twice, the second one is used.

For example:

0 /obj/chain_bone1/cregion 0 1.0
0 /obj/chain_bone1/cregion 0 2.0

This causes the first entry to be ignored (a weighting of 2.0 is used).

The weight field is used to prescribe the relative amount of influence a region has on a point. It can be any number. The range of the weights computed by TouchDesigner are specified by the Inner/Outer Weight parameter of each Capture Region (please see Capture Region SOP). The easiest way to a capture Override File is to use the Save Override File button (see below) and start from the file produced by TouchDesigner.

Save File - The file specified here can be used as a "working file" to save the point weighting of all the points or a selected subset of points. The file format for the capture override files is fairly straight-forward (see above), so this is a good place to start if you need to do custom overriding.

Increment Save File - This increments the Save File name before saving. Be careful about turning this option off because there is no warning or confirm dialog to prevent you from overwriting an .ocapt file.

Save All Data to File - This saves the point weighting of all points to the Save File.

Save Selected Points to File - This saves the point weighting only for the points that are selected in the viewport.

Note: you must be editing this particular SOP in the Viewport for this selection to apply to this SOP.

See Also