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 EtherDream CHOP or Helios DAC 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.
LASERS ARE DANGEROUS IF NOT HANDLED WITH RESPECT - DAMAGE TO YOUR OR THE AUDIENCE'S EYE SIGHT IS A VERY REAL RISK
- 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.
- If you plan to routinely handle Lasers, think about becoming a certified Laser Safety Officer. Courses are available from ILDA directly: ILDA Laser Safety Courses
Parameters - Laser Page
active - When disabled, the CHOP will zero out all channels.
source - ⊞ - Select the source operator type for the laser image.
sop- Use a SOP as the source for the Laser image. Appart from position attributes, the SOP's point color attributes are used to determine the color output.
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 - Path to the SOP.
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.
Input Sample Rate
inputrate - Specify the Sample Rate the input source will be sampled at. This can be lower than the output sample rate. If lower than the output sample rate then the output will be resampled (same as if put through a Resample CHOP).
Output Sample Rate
outputrate - The sample rate of the 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 - Lets you swap the x and y axis of the output.
xscale - Control the horizontal scale of the output.
yscale - Control the vertical scale of the output.
rotate - Control the rotation of the output.
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.
vertexorder - Output the points in the same order as the vertices of each polygon, instead of the order in which the points are defined in the geometry.
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 Vertex Hold
minverthold - The minimum value of the vertex hold of a point. The value of the vertex hold of a point is calculated linearly in the range from the minimum to maximum vertex 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 vertex hold of the point will be the minimum value.
Maximum Vertex Hold
maxverthold - The maximum value of the vertex hold of a point. See Minimum Vertex Hold for more details. When the angle at the point is 0 degrees, then the vertex hold will be the maximum value. If the maximum value is lower than the minimum then the maximum will be clamped upward.
camera - Specify the path to a Camera COMP used to draw a SOP from the cameras view.
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.
redscale - Set the intensity of the Red Channel.
greenscale - Set the intensity of the Green Channel.
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.
colordelay - Set the delay in ms of the color channels in the output.
Parameters - Common Page
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 - 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.
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
autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.
exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).
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An Operator Family that reads, creates and modifies 3D polygons, curves, NURBS surfaces, spheres, meatballs and other 3D surface data.
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.
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.
The term "Frame" is used (1) in the Timeline, (2) as a time-unit in CHOPs, (3) as a time-unit in TOPs, and (4) with movies images which are read and created with TOPs.
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 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 only 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.
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.
Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a Network Editor by pressing the keyboard shortcut 'p'.