Experimental:Laser CHOP

Summary

The Laser CHOP produces channels that can drive a laser projector. It uses the points and lines of a SOP or CHOP and outputs the channels at a specified sample rate, typically 10,000 to 96,000 samples per second. The Laser CHOP gives optimal control over the movement of the reflectors of the laser projector as well as enhanced color control. In particular, it gives better control of lines being straight, end-points being not cut off or over-drawn, and eliminating tails, all adjustable using a set of parameters.

The resulting channels can be sent to the Laser Device CHOP in case of controlling a Laser via the ILDA Protocol, or the Audio Device Out CHOP in case of using one of LaserAnimation Sollinger's AVB capable devices, where the audio is output via the Audio Device Out CHOP to a low-latency AVB-ready audio device like those from MOTU, RME, LaserAnimation Sollinger or Apple macOS.

LaserAnimation Sollinger's AVB2ILDA devices give you access to features for the professional sector including 24bit resolution on the x/y signal and all color channels. Additionally the AVB2ILDA device includes software for electronic masking, making it possible to limit the laser output for certain areas (for example to protect scanning areas such as auditoriums or sectors with optical equipment). Also packaged is a color correction tool that includes individual control of the color delay for 3 colors as well as a Digital Geometric Correction to allow for projection on for example uneven surfaces. (The Laser CHOP replaces the Scan CHOP.)

The CHOP was developed with the help of LaserAnimation Sollinger who guided us in speccing and implementing the necessary parameters, especially in regards of the blanking timing settings.

Tip: See the OP Snippets for setup and usage examples.

LASERS ARE DANGEROUS - DAMAGE TO YOUR OR THE AUDIENCE'S EYE SIGHT IS A VERY REAL RISK

• If you plan to use lasers

1. Understand all the laws and regulations for laser operation in your area.
2. Become a certified Laser Safety Officer (this is required by law in some areas). Courses are available from ILDA directly: ILDA Laser Safety Courses

• Make sure an emergency stop button is close to you at all times.
• Do not let anyone enter the laser projection area unless all precautions have been taken to limit the output.
• Make sure there are no reflective surfaces in the projection area that might cause the beam to reflect unintendedly.

Corner Points

The Laser CHOP categorizes input points as either corner points or guide points. Prior to the 2023.30000 series of builds, all points were considered corner points.

All input points are corner points by default. To set a point as either a corner or guide point, use a boolean attribute named "LasCorner" for SOP inputs, or a "lascorner" channel for CHOP inputs. LasCorner=true means it is a corner point.

Guide points are simply points that help move the laser along a path or curve, and they will not have abrupt changes in line direction between the two line segments they're a part of. Guide points are only output once and never repeated. Guide points are also useful for point interpolation when stepping is done along the curve.

Corner points essentially define the start/end points of an individual line strip on the laser. Interpolation of color and point position stepping is done between corner points, with guide points used for weighting. Corner points should also be used when there is an abrupt change in the laser direction (eg. right or acute angle) so that appropriate hold points can be added to increase sharpness of the image.

Corner points repeat as a function of their angle and the corner hold parameters. Additionally, for extra per-point control, corner hold look-up factor and hold add can be used through special attributes in SOP inputs, or channels in CHOP inputs:

• "LasCornerHoldAdd" (SOP) or "lascornerholdadd" (CHOP)
• "LasCornerHoldLookupFactor" (SOP) or "lascornerholdlookupfactor" (CHOP)

Corner hold repeat is calculated as follows, where H is the hold value calculated from the angle/parameters:

NumRepeatPoints = HoldAdd + HoldLookupFactor * H

See also: Laser Device CHOP

laserCHOP_Class

Parameters - Laser Page

Active active - When disabled, the CHOP will zero out all channels.

Source OP source - ⊞ - Select the source operator type for the laser image.

• SOP sop - Use a SOP as the source for the Laser image. Apart from position attributes, the SOP's point color attributes are used to determine the color output.

• CHOP chop - Use a CHOP as the source for the Laser image. The CHOP expects x and y channels and every sample will be interpreted as a point to be drawn. To draw multiple shapes, also specify an id named channel to identify each shape. All other channels will be interpreted as color channels and blanking will be applied to those. This makes it possible to drive Lasers that have more than just rgb diodes active.

SOP sop - Path to the SOP.

CHOP chop - Path to the CHOP. The input CHOP must have x, y channels for the point positions. In addition, it also supports z, r, g, b, and id channels. The id channel is used for grouping points together as a single shape. By default when no id channel is present, each point is separate and unconnected. Additional and arbitrarily named colour channels may be added for laser projectors that accept more than just r, g, b. Additional channels include: "lascorner", "lascornerholdadd", and "lascornerholdlookupfactor".

Output Sample Rate outputrate - The sample rate of the Laser CHOP, and the sample rate at which it will output to the laser. With the default 48000 samples per second and a 60fps frame rate, the Laser CHOP can output 800 position and color values per frame.

Swap Output swap - Lets you swap the x and y axis of the output.

X Scale xscale - Control the horizontal scale of the output.

Y Scale yscale - Control the vertical scale of the output.

Rotate rotate - Control the rotation of the output.

Camera camera - Specify the path to a Camera COMP used to draw a SOP from the cameras view.

Update Method updatemethod - ⊞ - Control how the Laser CHOP pulls data from its source.

In most cases you will want to keep this at the default setting "When All Points Drawn".

There is a specific usage case that requires the "Every Frame" update method. Background is that the Laser CHOP might have to draw the input values over multiple frames. For example given a source with 200 sampling values. After applying all blanking and step sizes at a certain sample rate, the Laser might need more than one frame to draw the full image. The effect will be visible by the Laser image flickering. With the default setting, the Laser will grab a new set of samples from its input once it has completed drawing all previous values. With the "Every Frame" update method, the Laser will grab the updated values for the remaining samples after each frame.

• When All Points Drawn alldrawn - The Laser CHOP will read the source data once all points of the previous frame have been drawn.

• Every Frame everyframe - The Laser CHOP will update the input every frame, no matter if it finished drawing the previous frame or not.

Frame Start Pulse startpulse - When enabled, will insert a sample with all colors set to -1 at the beginning of the laser frame.

Debug Channel debugchan - When enabled, an extra channel with point state will be included:

• -1 : Frame Start Pulse
• 0 : Color
• 1 : Corner Hold Point
• 2 : Start Point Hold Time
• 3 : Pre Blank On
• 4 : Post Blank On
• 5 : Blanking
• 6 : Pre Blank Off
• 7 : Post Blank Off

Parameters - Scanning Page

Step Size stepsize - The distance each x,y can change while outputing color.

Blanking Step Size bstepsize - The distance each x,y can change while not outputing color (blanking).

Minimum Corner Hold mincornerhold - The minimum value of the corner hold of a point. The value of the corner hold of a point is calculated linearly in the range from the minimum to maximum corner hold, based on the steepness of the angle at the point. This angle is calculated with the following three points: the previous point, the point itself, and the next point. Example: when the angle at the point is 180 degrees then the corner hold of the point will be the minimum value.

Maximum Corner Hold maxcornerhold - The maximum value of the corner hold of a point. See Minimum corner Hold for more details. When the angle at the point is 0 degrees, then the corner hold will be the maximum value. If the maximum value is lower than the minimum then the maximum will be clamped upward.

Corner Hold Lookup CHOP cornerholdchop - Reference to a CHOP to use as the custom lookup curve when interpolating from min to max hold. By default (ie. when no CHOP is specified), then it is linearly interpolated.

Closed Shape Overlap closedoverlap - For closed shapes, the number of points (specified in milliseconds) to overlap the start/end, to utilize color interpolation and get a more uniform shape.

Parameters - Color Page

These parameters let you control how the color channels for the Laser are created. Especially paying attention to the blanking settings which will have to be adjusted matching the capabilities of your laser projector.

Blanking is the capability of a laser projector to rapidly turn on / off the laser when displaying animations. For example when displaying multiple shapes, the laser needs the ability of blanking to omit the empty spots between the shapes. As the laser's mirrors are driven by motors, the positional data that is send to the laser is likely to be ahead of the actual mirror position - the mirror must catch up to the data. The Color data though is in time and as a result the effect can be visible tails at points where the laser switches off its color. Adjusting the blanking parameters can help prevent this.

Red Scale redscale - Set the intensity of the Red Channel.

Green Scale greenscale - Set the intensity of the Green Channel.

Blue Scale bluescale - Set the intensity of the Blue Channel.

Pre Blanking On Delay preblankon - Set the time in ms the Laser should wait at a position before turning the color output off.

Post Blanking On Delay postblankon - Set the time in ms the Laser should wait at a position after turning the color output off.

Pre Blanking Off Delay preblankoff - Set the time in ms the Laser should wait at a position before turning the color output on.

Post Blanking Off Delay postblankoff - Set the time in ms the Laser should wait at a position after turning the color output on.

Start-Point Hold Time starthold - Set the time in ms the Laser should wait at the first point of a new data frame before continuing on.

Color Delay colordelay - Set the delay in ms of the color channels in the output.

Interpolate Colors interpcolors - When enabled, interpolates colors between points.

Brightness Curve Lookup CHOP brightnesscurvechop - Reference a CHOP to use as a custom look-up for soft-edge blending of closed shapes.

Parameters - Common Page

Time Slice timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.

Scope scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.

Sample Rate Match srselect - ⊞ - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.

• Resample At First Input's Rate first - Use rate of first input to resample others.

• Resample At Maximum Rate max - Resample to the highest sample rate.

• Resample At Minimum Rate min - Resample to the lowest sample rate.

• Error If Rates Differ err - Doesn't accept conflicting sample rates.

Export Method exportmethod - ⊞ - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.

• DAT Table by Index datindex - Uses the docked DAT table and references the channel via the index of the channel in the CHOP.

• DAT Table by Name datname - Uses the docked DAT table and references the channel via the name of the channel in the CHOP.

• Channel Name is Path:Parameter autoname - The channel is the full destination of where to export to, such has geo1/transform1:tx.

Export Root autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.

Export Table exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).

Info CHOP Channels

Extra Information for the Laser CHOP can be accessed via an Info CHOP.

Common CHOP Info Channels

• start - Start of the CHOP interval in samples.

• length - Number of samples in the CHOP.

• sample_rate - The samplerate of the channels in frames per second.

• num_channels - Number of channels in the CHOP.

• time_slice - 1 if CHOP is Time Slice enabled, 0 otherwise.

• export_sernum - A count of how often the export connections have been updated.

Common Operator Info Channels

• total_cooks - Number of times the operator has cooked since the process started.

• cook_time - Duration of the last cook in milliseconds.

• cook_frame - Frame number when this operator was last cooked relative to the component timeline.

• cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.

• cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.

• cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.

• cooked_this_frame - 1 if operator was cooked this frame.

• warnings - Number of warnings in this operator if any.

• errors - Number of errors in this operator if any.

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An Operator Family which operate on Channels (a sequence of numbers (Samples)) which are used for animation, audio, mathematics, simulation, logic, UI construction, and data streamed from/to devices and protocols.

A Operator Family that reads, creates and modifies 3D points, polygons, lines, particles, surfaces, spheres and meatballs. Particles and point clouds are now done primarily on the GPU using TOPs.

Any of the procedural data operators. OPs do all the work in TouchDesigner. They "cook" and output data to other OPs, which ultimately result in new images, data and audio being generated. See Node.

The location of an operator within the TouchDesigner environment, for example, /geo1/circle1, a node called circle1 in a component called geo1. The path / is called Root. This path is displayed at the top of every Pane, showing which Component's network you are currently in. To refer instead to a filesystem folder, directory, disk file or http: address, see Folder.

samples-per-second of a CHOP. Each CHOP in your network has a sample rate. In contrast, the overall timeline has a Frame Rate, which is the number of frames to cook and display per second, generally your monitor display frequency, default 60.

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

The term "Frame" is a measurement of time used (1) in the Timeline, (2) as a time-unit in CHOPs, and (3) as a time unit in movie files that are read into TOPs and written out from TOPs. The frame rate is the frames per second (FPS).

To "pulse" a parameter is to send it a signal from (1) an exported CHOP channel or (2) a python command or (3) 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 parameter in a Speed CHOP. A pulse from a CHOP is typically a 0 to 1 to 0 signal in an exported channel.

A CHOP outputs one or more channels, where a channel is simply a sequence of numbers (Samples), representing motion, audio, etc. Channels are passed between CHOPs in TouchDesigner networks. Channels can be Exported to Parameters.

Each SOP has a list of Points. Each point has an XYZ 3D position value plus other optional attributes. Each polygon Primitive is defined by a vertex list, which is list of point numbers.

A Link. The grey dashed lines between nodes is a Reference or Link that indicates one operator is getting data from another operator from any Operator Family.

The grey dashed lines between nodes is a Reference (or Link). A Reference is (1) a Parameter Reference, a parameter in an OP that is a name or path to another operator, (2) a Node Reference, an expression in a parameter or DAT script that contains the name or path of another operator, (3) a DAT Cell Reference or (4) a CHOP Channel Reference.

A Link or Reference is a dashed line between nodes that represent other data flowing between nodes. Examples are CHOP Exports, node Paths in parameters, and expressions in parameters referencing CHOP channels, DAT tables and other nodes. In contrast is a Wire that connects nodes in the same Operator Family.

A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the set of short channels that contain the CHOP channels' samples between the last and the current cook frame.

A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator. TOPs have Channel Mask, a similar feature.

Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.

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

Every operator in TouchDesigner has a set of control Parameters that can be integer or floating point numbers, menus, binary toggles, text strings or operator paths, which determine the output of the operator.

TouchDesigner is a hierarchy of components. "root" is the top-most network in the hierarchy. The Network Path or Path for root is simply /. A typical path is /project1/moviein1.