# Difference between revisions of "Bullet Solver COMP"

## Summary

In a Bullet Dynamics system, the Bullet Solver COMP is analogous to the world/simulation in which actors/bodies (ie. Actor COMPs) operate. A Bullet Solver COMP contains any number of actors/bodies (Actor COMPs) or forces (Force COMP/Impulse Force COMP), and as the name suggests it also uses the Bullet Physics API to step through the simulation.

The Bullet Solver COMP runs a Bullet simulation based on some simulation parameters (eg. linear multiplier or angular multiplier) and updates the transformations of the Actor COMPs contained within it as the simulation progresses forward. The simulation can be paused, slowed down, sped up, or restarted using the parameters on the COMP.

The Bullet Solver COMP simulation operates in a vacuum, so there will be no air resistance applied to any actors in the simulation. The simulation is stepped at the given sample rate, and the Actor COMP transform is updated accordingly. These transformations are the same results displayed in the Bullet Solver CHOP.

The Actor COMPs referenced by the Bullet Solver COMP do not need to be inside its network. They can be anywhere as long as they are not already referenced by another Bullet Solver COMP.

## Parameters - Solver Page

Actors actors - The Actor COMPs to include in the simulation. These actors cannot already be a part of another Bullet Solver COMP.

Global Forces forces - The Force COMPs to include in the simulation. These forces are global forces and will be applied to all non-static actors in the simulation.

Gravitational Acceleration gravity - - Gravity applied to all actors in the simulation in m/s^2. Gravity is applied to actors irrespective of their mass.

• X gravityx -
• Y gravityy -
• Z gravityz -

Dimension dimension - - The dimension of the simulation. The options in this menu can also be recreated using the linear/angular multiplier parameters.

• 1D 1d - Actor is constrained to linear velocity only on the X axis, with no angular velocity (linmult 1,0,0 and angmult 0,0,0)
• 2D 2d - Actor is constrained to linear velocity only on the XY plane, with angular velocity only around the Z axis (linmult 1,1,0 and angmult 0,0,1)
• 3D 3d - Actor is not constrained and can move in any direction: X, Y, or Z. Similarly, the Actor can also rotate in any direction: X, Y, or Z (linmult 1,1,1 and angmult 1,1,1)

Linear Multiplier linmult - - A multiplier for the linear velocities of the actors in the simulation. For example, if linmult is (0, 1, 1) then the actors can move linearly at normal speed on the Y and Z axes but cannot move in the X direction. These values are multiplied internally by the values from dimension. For example, if the dimension is 2D and linmult is (0, 1, 1) then the only direction the actors can move is along the Y axis because 2D is constraining on the Z and this parameter is constraining on the Y.

• X linmultx -
• Y linmulty -
• Z linmultz -

Angular Multiplier angmult - - A multiplier for the angular velocities of the actors in the simulation. For example, if angmult is (1, 0, 0) then the actors can only rotate on the X axes. These values are multiplied internally by the values from dimension. So, if dimension is 2D and angmult is (1, 0, 0) then the actor will not be able to rotate in any direction because 2D constrains rotation only to the Z axis, and this parameter is constraining it only to the X axis.

• X angmultx -
• Y angmulty -
• Z angmultz -

Initialize Sim and Collision Shapes initall - Resets all bodies to their initial state (ie. position, orientation, velocity) and recreates their collision shapes. This parameter is equivalent to pulsing each Actor COMP's "Initialize Actor". Creating collision shapes can be time consuming in certain cases, so if it's not need then Initialize Sim should be used instead. Collision shapes need to be recreated if any of the SOPs used to create the collision shape change, or if the instancing OP changes.

Initialize Sim init - Reset all bodies to their initial state (ie. position, orientation, velocity). This will not begin stepping through the simulation, it will only initialize. NOTE: This will not reset the collision shapes of any Actor COMPs, "Initialize Sim and Collision Shapes" above or "Initialize Actor" on the Actor COMP should be used for that.

Start Sim start - Initialize the simulation and run it (begin stepping).

Play play - Play the simulation. Will step through the simulation when toggled on, but will not when it is toggled off (ie. it will be paused).

Sample Rate rate - The sample rate of the simulation. The sample rate affects the timestep, which is 1/rate   Simulation Speed simspeed - The speed of the simulation. It is a multiplier for the size of the timestep to slow down or speed up the simulation.

Feedback CHOP feedback - (see also: Bullet Solver CHOP) A reference to a CHOP to feedback. The Bullet Solver COMP will take the transform/velocity channels from the CHOP and override the respective actor's transform or velocity at the beginning of the next simulation step. If you feedback a Bullet Solver CHOP that has no change to the channel values in it, the simulation will act as normal as nothing is being overriden. This allows you do things like the example below. For example, to negate the velocity of every actor in a simulation you could use a Bullet Solver CHOP, put that into a Switch CHOP with the second input being the same CHOP only with the velocity channels negated. Then export a button pulse to the switch index and put the Switch CHOP into the Feedback CHOP parameter. Then, when the button is pressed for a single frame (pulsed) the velocities will be overridden and negated. The only channels required to feedback are the actor_id and body_id channels, all other channels are optional. The channel names should all be the same as in the Bullet Solver CHOP. In addition to the channels outputted in the Bullet Solver CHOP, force and torque can also be used. The channel names are force[xyz] and torque[xyz]. NOTE: scale cannot be used for feedback.

Perform Contact Test contacttest - Enables contact testing for all bodies in the simulation. Contact testing is used for the colliding and total_collisions channels on the Bullet Solver CHOP. Without this parameter enabled those channel values will not update. NOTE: Contact testing can be slow for lots of bodies.

Always Simulate alwayssim - When enabled the Bullet Solver COMP will simulate (ie. cook) every frame.

Callbacks DAT callbacks - A reference to a DAT with python callbacks. The available callbacks are: onCollision(solverComp, collisions), onFrameStart(solverComp), onFrameEnd(solverComp), onInit(solverComp), onStart(solverComp). A DAT with these callbacks will be automatically created and referenced when a Bullet Solver COMP is created. onCollision(solverComp, collisions) passes a list of all collisions occuring, and requires that Perform Contact test be enabled. collisions is a list of named tuples (bodyA and bodyB). bodyA and bodyB are the two bodies participating in the collision. bodyA and bodyB are Python Body Objects (see Body Class).

## Parameters - Xform Page

The Xform parameter page controls the object component's transform in world space.

Transform Order xord - - The menu attached to this parameter allows you to specify the order in which the changes to your Component will take place. Changing the Transform order will change where things go much the same way as going a block and turning east gets you to a different place than turning east and then going a block. In matrix math terms, if we use the 'multiply vector on the right' (column vector) convention, a transform order of Scale, Rotate, Translate would be written as T * R * S * Position.

• Scale Rotate Translate srt -
• Scale Translate Rotate str -
• Rotate Scale Translate rst -
• Rotate Translate Scale rts -
• Translate Scale Rotate tsr -
• Translate Rotate Scale trs -

Rotate Order rord - - The rotational matrix presented when you click on this option allows you to set the transform order for the Component's rotations. As with transform order (above), changing the order in which the Component's rotations take place will alter the Component's final position. A Rotation order of Rx Ry Rz would create the final rotation matrix as follows R = Rz * Ry * Rx

• Rx Ry Rz xyz - R = Rz * Ry * Rx
• Rx Rz Ry xzy - R = Ry * Rz * Rx
• Ry Rx Rz yxz - R = Rz * Rx * Ry
• Ry Rz Rx yzx - R = Rx * Rz * Ry
• Rz Rx Ry zxy - R = Ry * Rx * Rz
• Rz Ry Rx zyx - R = Rx * Ry * Rz

Translate t - - The three fields allow you to specify the amount of movement along any of the three axes; the amount, in degrees, of rotation around any of the three axes; and a non-uniform scaling along the three axes. As an alternative to entering the values directly into these fields, you can modify the values by manipulating the Component in the Viewport with the Select & Transform state.

• X tx -
• Y ty -
• Z tz -

Rotate r - - The three fields allow you to specify the amount of movement along any of the three axes; the amount, in degrees, of rotation around any of the three axes; and a non-uniform scaling along the three axes. As an alternative to entering the values directly into these fields, you can modify the values by manipulating the Component in the Viewport with the Select & Transform state.

• X rx -
• Y ry -
• Z rz -

Scale s - - The three fields allow you to specify the amount of movement along any of the three axes; the amount, in degrees, of rotation around any of the three axes; and a non-uniform scaling along the three axes. As an alternative to entering the values directly into these fields, you can modify the values by manipulating the Component in the Viewport with the Select & Transform state.

• X sx -
• Y sy -
• Z sz -

Pivot p - - The Pivot point edit fields allow you to define the point about which a Component scales and rotates. Altering the pivot point of a Component produces different results depending on the transformation performed on the Component.

For example, during a scaling operation, if the pivot point of an Component is located at -1, -1, 0 and you wanted to scale the Component by 0.5 (reduce its size by 50%), the Component would scale toward the pivot point and appear to slide down and to the left.

In the example above, rotations performed on an Component with different pivot points produce very different results.

• X px -
• Y py -
• Z pz -

Uniform Scale scale - This field allows you to change the size of an Component uniformly along the three axes.

Note: Scaling a camera's channels is not generally recommended. However, should you decide to do so, the rendered output will match the Viewport as closely as possible when scales are involved.

Constrain To constrain - Allows the location of the object to be constrained to any other object whose path is specified in this parameter.

Look At lookat - Allows you to orient your Component by naming the Component you would like it to Look At, or point to. Once you have designated this Component to look at, it will continue to face that Component, even if you move it. This is useful if, for instance, you want a camera to follow another Component's movements. The Look At parameter points the Component in question at the other Component's origin.

Tip: To designate a center of interest for the camera that doesn't appear in your scene, create a Null Component and disable its display flag. Then Parent the Camera to the newly created Null Component, and tell the camera to look at this Component using the Look At parameter. You can direct the attention of the camera by moving the Null Component with the Select state. If you want to see both the camera and the Null Component, enable the Null Component's display flag, and use the Select state in an additional Viewport by clicking one of the icons in the top-right corner of the TouchDesigner window.

Look At Up Vector lookup - - When specifying a Look At, it is possible to specify an up vector for the lookat. Without using an up vector, it is possible to get poor animation when the lookat Component passes through the Y axis of the target Component.

• Don't Use Up Vector - Use this option if the look at Component does not pass through the Y axis of the target Component.
• Use Up Vector - This precisely defines the rotates on the Component doing the looking. The Up Vector specified should not be parallel to the look at direction. See Up Vector below.
• Use Quaternions - Quaternions are a mathematical representation of a 3D rotation. This method finds the most efficient means of moving from one point to another on a sphere.
• Don't use up vector off -
• Use up vector on -
• Use quaternions quat -

Path SOP pathsop - Names the SOP that functions as the path you want this Component to move along. For instance, you can name an SOP that provides a spline path for the camera to follow.

Production Tip: For Smooth Motion Along a Path - Having a Component follow an animation path is simple. However, when using a NURBS curve as your path, you might notice that the Component speeds up and slows down unexpectedly as it travels along the path. This is usually because the CVs are spaced unevenly. In such a case, use the Resample SOP to redistribute the CVs so that they are evenly spaced along the curve. A caution however - using a Resample SOP can be slow if you have an animating path curve.

An alternative method is to append a Basis SOP to the path curve and change it to a Uniform Curve. This way, your Component will move uniformly down the curve, and there is no need for the Resample SOP and the unnecessary points it generates.

Roll roll - Using the angle control you can specify a Component's rotation as it animates along the path.

Position pos - This parameter lets you specify the Position of the Component along the path. The values you can enter for this parameter range from 0 to 1, where 0 equals the starting point and 1 equals the end point of the path. The value slider allows for values as high as 10 for multiple "passes" along the path.

Orient along Path pathorient - If this option is selected, the Component will be oriented along the path. The positive Z axis of the Component will be pointing down the path.

Orient Up Vector up - - When orienting a Component, the Up Vector is used to determine where the positive Y axis points.

• X upx -
• Y upy -
• Z upz -

Auto-Bank Factor bank - The Auto-Bank Factor rolls the Component based on the curvature of the path at its current position. To turn off auto-banking, set the bank scale to 0.

## Parameters - Pre-Xform Page

The Pre-Xform parameter page applies a transform to the object component before the Xform page's parameters are applied. That is, it is the same as connecting a Null COMP as a parent of this node, and putting same transform parameters in there as you would in the Pre-Xform page. In terms of matrix math, if we use the 'multiply vector on the right' (column vector) convention, the equation would be preXForm * xform * vector.

Apply Pre-Transform pxform - Enables the transformation on this page.

Transform Order pxord - - Refer to the documentation on Xform page for more information.

• Scale Rotate Translate srt -
• Scale Translate Rotate str -
• Rotate Scale Translate rst -
• Rotate Translate Scale rts -
• Translate Scale Rotate tsr -
• Translate Rotate Scale trs -

Rotate Order prord - - Refer to the documentation on Xform page for more information.

• Rx Ry Rz xyz -
• Rx Rz Ry xzy -
• Ry Rx Rz yxz -
• Ry Rz Rx yzx -
• Rz Rx Ry zxy -
• Rz Ry Rx zyx -

Translate pt - - Refer to the documentation on Xform page for more information.

• X ptx -
• Y pty -
• Z ptz -

Rotate pr - - Refer to the documentation on Xform page for more information.

• X prx -
• Y pry -
• Z prz -

Scale ps - - Refer to the documentation on Xform page for more information.

• X psx -
• Y psy -
• Z psz -

Pivot pp - - Refer to the documentation on Xform page for more information.

• X ppx -
• Y ppy -
• Z ppz -

Uniform Scale pscale - Refer to the documentation on Xform page for more information.

Reset Transform preset - This button will reset this page's transform so it has no translate/rotate/scale.

Commit to Main Transform pcommit - This button will copy the transform from this page to the main Xform page, and reset this page's transform.

Xform Matrix/CHOP/DAT xformmatrixop - This parameter can be used to transform using a 4x4 matrix directly. For information on ways to specify a matrix directly, refer to the Matrix Parameters page.

## Parameters - Render Page

The Display parameter page controls the component's material and rendering settings.

Material material - Selects a MAT to apply to the geometry inside.

Render render - Whether the Component's geometry is visible in the Render TOP. This parameter works in conjunction (logical AND) with the Component's Render Flag.

Draw Priority drawpriority - Determines the order in which the Components are drawn. Smaller values get drawn after (on top of) larger values.

Pick Priority pickpriority - When using a Render Pick CHOP or a Render Pick DAT, there is an option to have a 'Search Area'. If multiple objects are found within the search area, the pick priority can be used to select one object over another. A higher value will get picked over a lower value. This does not affect draw order, or objects that are drawn over each other on the same pixel. Only one will be visible for a pick per pixel.

Wireframe Color wcolor - - Use the R, G, and B fields to set the Component's color when displayed in wireframe shading mode.

• Red wcolorr -
• Green wcolorg -
• Blue wcolorb -

Light Mask lightmask - By default all lights used in the Render TOP will affect geometry renderer. This parmaeter can be used to specify a sub-set of lights to be used for this particular geometry. The lights must be listed in the Render TOP as well as this parameter to be used.

## Parameters - Extensions Page

The Extensions parameter page sets the component's python extensions. Please see extensions for more information.

Re-Init Extensions reinitextensions - Recompile all extension objects. Normally extension objects are compiled only when they are referenced and their definitions have changed.

Extension Object 1 extension1 - A number of class instances that can be attached to the component.

Extension Name 1 extname1 - Optional name to search by, instead of the instance class name.

Promote Extension 1 promoteextension1 - Controls whether or not the extensions are visible directly at the component level, or must be accessed through the .ext member. Example: n.Somefunction vs n.ext.Somefunction

## Parameters - Common Page

The Common parameter page sets the component's node viewer and clone relationships.

Node View nodeview - - Determines what is displayed in the node viewer, also known as the Node Viewer. Some options will not be available depending on the Component type (Object Component, Panel Component, Misc.)

• Default Viewer default - Displays the default viewer for the component type, a 3D Viewer for Object COMPS and a Control Panel Viewer for Panel COMPs.
• Operator Viewer opviewer - Displays the node viewer from any operator specified in the Operator Viewer parameter below.

Operator Viewer opviewer - Select which operator's node viewer to use when the Node View parameter above is set to Operator Viewer.

Keep in Memory keepmemory -

Enable Cloning enablecloning - Control if the OP should be actively cloned. The Pulse button can be used to instantaneously clone the contents.

Enable Cloning Pulse enablecloningpulse -

Clone Master clone - Path to a component used as the Master Clone.

Load on Demand loadondemand - Loads the component into memory only when required. Good to use for components that are not always used in the project.

External .tox externaltox - Path to a .tox file on disk which will source the component's contents upon start of a .toe. This allows for components to contain networks that can be updated independently. If the .tox file can not be found, whatever the .toe file was saved with will be loaded.

Reload .tox on Start reloadtoxonstart - When on (default), the external .tox file will be loaded when the .toe starts and the contents of the COMP will match that of the external .tox. This can be turned off to avoid loading from the referenced external .tox on startup if desired (the contents of the COMP are instead loaded from the .toe file). Useful if you wish to have a COMP reference an external .tox but not always load from it unless you specifically push the Re-Init Network parameter button.

Reload Custom Parameters reloadcustom - When this checkbox is enabled, the values of the component's Custom Parameters are reloaded when the .tox is reloaded.

Reload Built-In Parameters reloadbuiltin - When this checkbox is enabled, the values of the component's built-in parameters are reloaded when the .tox is reloaded.

Save Backup of External savebackup - When this checkbox is enabled, a backup copy of the component specified by the External .tox parameter is saved in the .toe file. This backup copy will be used if the External .tox can not be found. This may happen if the .tox was renamed, deleted, or the .toe file is running on another computer that is missing component media.

Sub-Component to Load subcompname - When loading from an External .tox file, this option allows you to reach into the .tox and pull out a COMP and make that the top-level COMP, ignoring everything else in the file (except for the contents of that COMP). For example if a .tox file named project1.tox contains project1/geo1, putting geo1 as the Sub-Component to Load, will result in geo1 being loaded in place of the current COMP. If this parameter is blank, it just loads the .tox file normally using the top level COMP in the file.

Re-Init Network reinitnet - This button will re-load from the external .tox file (if present), followed by re-initializing itself from its master, if it's a clone.   TouchDesigner Build:

Actor • Ambient Light • Animation • Base • Blend • Bone • Bullet Solver • Button • Camera Blend • Camera • Component • Constraint • Container • Engine • Environment Light • FBX • Field • Force • Geometry • Handle • Impulse Force • Light • List • Null • Nvidia Flex Solver • Nvidia Flow Emitter • OP Viewer • Parameter • Replicator • Select • Shared Mem In • Shared Mem Out • Slider • Table • Time • USD • Widget • Window

An Operator Family that contains its own Network inside. There are twelve 3D Object Component and eight 2D Panel Component types. See also Network Path.

samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.

An Operator Family which operate on Channels (a series of numbers) which are used for animation, audio, mathematics, simulation, logic, UI construction, and many other applications.

An Operator Family that manipulates text strings: multi-line text or tables. Multi-line text is often a command Script, but can be any multi-line text. Tables are rows and columns of cells, each containing a text string.

An Operator Family that contains its own Network inside. There are twelve 3D Object Component and eight 2D Panel Component types. See also Network Path.

The location of an operator within the TouchDesigner environment, for example, /geo1/torus1, a node called torus1 in a component called geo1. The path / is called Root. To refer instead to a filesystem folder, directory, disk file or http: address, see Folder.

An Operator Family that reads, creates and modifies 3D polygons, curves, NURBS surfaces, spheres, meatballs and other 3D surface data.

An Operator Family that associates a shader with a SOP or Geometry Object for rendering textured and lit objects.

Any component can be extended with its own Python classes which contain python functions and data.

The component types that are used to render 3D scenes: Geometry Component contain the 3D shapes to render, plus Camera, Light, Ambient Light, Null, Bone, Handle and other component types.

The viewer of a node can be (1) the interior of a node (the Node Viewer), (2) a floating window (RMB->View... on node), or (3) a Pane that graphically shows the results of an operator.

A custom interactive control panel built within TouchDesigner. Panels are created using Panel Components whose look is created entirely with TOPs.

To pulse a parameter is to send it a signal from a CHOP or python or a mouse click that causes a new action to occur immediately. A pulse via python is via the .pulse() function on a pulse-type parameter, such as Reset in a Speed CHOP. A pulse from a CHOP is typically a 0 to 1 to 0 signal in a channel.

Cloning can make multiple components match the contents of a master component. A Component whose Clone parameter is set will be forced to contain the same nodes, wiring and parameters as its master component. Cloning does not create new components as does the Replicator COMP.

TouchDesigner Component file, the file type used to save a Component from TouchDesigner.

TOuch Environment file, the file type used by TouchDesigner to save your project.

Every component contains a network of operators that create and modify data. The operators are connected by wires that define where data is routed after the operator cooks its inputs and generates an output.