Houdini 13.0 Nodes

interface version 1

Builds the bounding box for animated input geometry.

This operator can evaluate its input geometry over a frame range, merge it into a single geometry, and compute the resulting bounding box. The results are also returned as numeric parameter values (so they can be referred to in expressions, etc).

  • Bounds of the view frustrum of an animated camera: a common technique for determining the visible 3D area of a shot (used with a Camera Frustrum qL SOP). The color-code indicates the relative timing of each geometry snapshot.

This operator can be very useful for DOP solvers that have bounding box settings for spatial limits (e.g. fluids or volumetrics).

With this node, such limits can be easily approximated, even (especially) when considering animated geometry.

Currently this operator only calculates non-oriented bounding boxes.

Tip

A practical example: when doing fluid simulations, the bounding box size and center output values can be directly linked to the volume limit parameters of a Flip Solver DOP.

This allows for completely procedural simulation setups – no need to adjust the limits by hand after geometry or animation changes. (The bounding geometry itself could be constructed from actual scene objects that are involved in the simulation.)

Tip

For heavier geometry, use larger frame step values and “Bounding Box” detail mode. (You can also reduce the geometry detail by “manual” preprocessing before passing it to this operator, e.g. keeping only every n-th primitive, etc.)

Although the overall bounds computation might happen to be expensive, it also has to be computed once (unless the input geometry animation changes).

Parameters

Group, Group Type

Allows to specify a subset of the entire geometry to work with.

Convert Input to Polygons

The input geometry will be converted to polygons before the bounding box calculations. This can be useful when dealing with more esoteric geometry types (e.g. implicit primitives).

Geometry Detail

The detail level of each individual geometry that will be merged together for the bounding box computation.

Default

Use the input geometry as it is. It gives the exact same result as Points Only, but uses more memory. It can be useful for more detailed guide displays, however.

Points Only

Since bounding boxes are calculated from geometry points, there’s no reason to keep anything else but the points.

Bounding Box

Replace each geometry sample from the animation with its bounding box. It might be useful for heavy input geometry. (The final result box will be somewhat larger.)

Centroids

Replace each geometry sample with a single point at its centroid.

This is intended to be a rough feedback for the motion path of the input geometry centroid. It is not reliable for an all-encompassing bounding box.

Frame Range (Start, End, Inc)

The input geometry will be evaulated multiple times within this range, the results merged, and from that will the final bounding box be computed.

The frame step value is important: for heavier geometry, keep it as low as possible, but without losing detail from the animation (the visual feedback of the guide display can be helpful).

(Usually it’s enough to sample every n-th frame – the results will still be acceptable, and with a much smaller speed/memory impact.)

Also note that for all fields fractional values are supported (so non-integer frame step values are valid and allowed).

Minimum Size, Lower Padding, Upper Padding

Adjustments to the final bounding box (see Bound SOP for details.)

Output Type

Geometry to output: final bounding box, or the geometry “trail” the final bounds are computed from. The output values (below) are not affected by this setting.

Show Guide

The guide display shows all the geometry that is merged together from the individual animation frames. It can be useful for adjusting geometry detail and frame step (Inc) settings.

Guide Colors

The guide geometry will be displayed with a color gradient to indicate the movement of the trail over time. (The gradient is pink/blue-to-red, where the pink/blue is mapped to the beginning of the time range, and red is to the end.)

Add 'bounds' Name Prefix

Adds the “BOUNDS_” prefix to the node name. (This allows easier picking of the node from an UI selection list – it also provides an unified naming scheme for Bounds nodes).

Output
Values

These contain various numeric results of the final bounding box (size and center, coordinates of opposite corners).

These parameters can be linked to other nodes (“Paste Copied References”) wherever necessary.

Link to Container

This utility tab allows quick and easy copying (or connecting) of the boundary output values to any container (D)OP.

Container OP Path

Path to the container-type (D)OP. Any operator can be specified that has size/center parameters to define its boundaries.

Parms (size/center)

Names of the size and center parameters on the target container node. The defaults are center and t (these are compatible with all regular DOP containers).

Link to Container

Pressing this button will create relative expression references on the target container. The references will point to the output Size and Center values on this operator.

Tip

Linking boundary values to container dimension parameters one can create full-procedural setups (e.g. by linking the emitter geometry boundaries to the initial dimensions of a volume container).

Copy Current Values

Pressing this button will copy the current size and center values to the target container. No expression links will be created (or deleted).

Release Notes

interface version 1 —

2014-05-07

  • Group parameter now works properly

  • Some UI/help streamlining

  • Added Centroids option for Geometry Detail

2014-03-10

  • Added main help image.

2014-01-16

  • Added support for fractional frame increments (with a limit of 0.01).

2014-01-15

  • Added bbox link preset for FLIP fluid solver maximum volume limit parameters.

2013-09-15

  • Added more presets to Link to Container parameters

2013-09-12

  • Added frame range presets

  • Added “Link to Container” output functionality

2013-08-27

  • Added colored guide option to indicate trail direction over time

  • Minor UI changes

2013-08-13

  • Attributes/groups are kept if the output is “trailed geometry”.

2013-05-08

  • Added “Convert to Polygons” toggle.

2013-04-22

  • Changed default node color to light green (the “referred-to” color).

  • Published the 'Editable' switch in the UI for the output expressions.

2013-04-18

  • Supports Group parameter

  • Distinctive node color

  • Displays animation range in network editor (descriptive parm)

  • Convenience button for node name prefixing (“BOUNDS_<name>”)

2013-04-14

The first frame of the range were often not added to the overall bounding box (the usual “remainder issue”). This is now fixed.

2013-04-10

First version.