/ Examples / Control / CCImageSampler

Wherein we examine images as a means to express parameter changes.

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The Example

In this example we filter a repeating note sequence using the CCImageSampler node. The image lookup locations are generated by the CCGen2D node. In this example we use the time-varying image samples to control the parameters of a BandPass filter node.

At right is the image we're using for this example. As detailed below we use the red and green channels of this arbitrary image to control the filter parameters. We can see faint yellow dots representing the sample positions in the Image Editor.

The CCGen2D node generates the yellow dots dynamically and updates the image overlay during performance. You can paint or draw into the image and when you save your changes, CCImageSampler automatically reloads it and thus modifies the peformance.

When a sample encounters "hot" pixel values the extreme filter parameters are delivered to the filter. The hand-painted grayscale lines produce a rhythm click as the generator's samples encounter them.

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ImageSampler Node

Controller is a connection point for the upstream generator of sample image positions. CCImageSampler listens on this connection for ImageXY or ImageX/ImageY control messages. Values are normalized pixel coordinates between 0 and 1. Without an upstream connection the CCImageSampler receives no coordinates and therefore produces no image samples.

Image is the name of the image to sample. You can drag & drop an image from the workspace panel or enter the filename directly. Clicking on the arrow to its right causes the image to be displayed in an Image Editor panel.

RedCC controls the name of the control-change message the CCImageSampler produces on its output when the red channel of the image is sampled. Here, we see that the red channel controls Cutoff which happens to be the BandPass parameter for the filter center.

RedRange causes the pixel sample value between 0 and 1 to be remapped into a range appropriate for RedCC. Here we vary the cutoff frequency between 200 and 2000 Hertz.

GreenCC establishes the name of the CC message associated with green channel samples. Here, we see that the green channel controls Bandpass's Quality parameter.

GreenRange remaps the green channel values from 0-1 onto 1-6.

BlueCC, AlphaCC are empty and this means that their pixel values will not produce any CC messages.

Gen2D Node

The Gen2D node generates 2 dimensional control signals and is the sibling of our 1D CCGenerator. Since our goal is to generate sample points for CCImageSampler this is the perfect tool for the job. Gen2D generates a rich collection of samples with only a few easily mastered parameters. As you play with the parameters it is very helpful to have the Image Editor panel opened in an adjacent panel.

Controller is a connection point for controlling the CCGen2D node. Here it is unused but the mind boggles at the idea of automating some of these parameters.

CC Name is the name of the CC message we generate. ImageXY was chosen because this is the name required by CCImageSampler.

Target Node allows you to target a subnode in a node-group. Here it is unused.

Generator selects the pattern generator from:

• Random produces a random point in the 2D plane.
• Random Walk produces a random walk across the 2D plane.
• Perlin produces a smoother random walk across the 2D plane.
• Lissajous produces patterns ranging from classic oscilloscope images to circles and ellipses.
• Phasor can be used to scan the 2D plane linearly in either/both X and Y.

In this example we selected Phasor with carefully selected values for FreqX and FreqY to produce a Matrix-like raining pixel effect.

Rate controls the CC generator execution rate. At 10::ms we generate 100 samples per second. Changing rate may interact with your FreqX/Y settings so its usually wise to adopt a fixed value before investing heavily in tweaking the remaining parameters.

FreqX, FreqY independently control the X and Y pattern frequency.

PhaseX, PhaseY independently control the X and Y phase or pattern offset.

ScaleX, ScaleY independently control the X and Y scale of the pattern. Usually these values should be less than 1, though there are times where larger values are useful.

OutputMin, OutputMax remaps the [-1, 1] values of the pattern generator onto the coordinate range required by the CC consumer. Since we're targeting CCImageSampler / ImageXY, we'd like our values to reside in the [0-1] range. Values within thsi range can be used to constrain samples to a subset of the entire image.