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Convolution Visualizer

Visualize continuous and discrete convolution step by step. Slide the flipped kernel across the signal and see the output build.

Tested tool guide Tested browser tools Checked August 16, 2026

What Convolution Visualizer does, with a checked example

Convolution Visualizer exposes the overlap behind continuous and discrete convolution. It flips the kernel, moves it across the signal, and shows how the products at each position contribute to the output. This makes the tool useful for connecting the convolution formula to filtering and impulse-response behavior. The common source of confusion is the flip: sliding an unflipped kernel describes cross-correlation, not convolution.

Worked example

A concrete input and expected output from the current implementation.

Input

Discrete signal x[n] = [1, 2]; kernel h[n] = [1, 1]; both begin at n = 0

Expected output

Full convolution y[n] = [1, 3, 2] for n = 0, 1, 2

The output samples are 1*1 = 1, then 1*1 + 2*1 = 3, then 2*1 = 2. The output has three samples because the two length-2 sequences overlap at three distinct shifts.

How the result is produced

1

Discrete sliding sum

For discrete sequences, the value at output index n is the sum of x[k]h[n-k] over the samples that overlap. At each step, the visualizer associates the current alignment with its pointwise products and their sum. Moving through every alignment builds the full finite convolution from its first partial overlap to its last.

2

Continuous overlap integral

For continuous signals, the corresponding value at shift t is the integral of x(tau)h(t-tau) over tau. The flipped and shifted second function is multiplied by the first wherever their supports overlap. The area under that product is one point of the convolution output, so changing the shift traces the resulting function.

Good uses

  • Checking by hand how a short finite impulse response kernel transforms a discrete signal.
  • Seeing why convolution with an impulse reproduces a shifted or scaled version of the other signal.
  • Comparing convolution with cross-correlation when kernel reversal changes the output.

Limits and checks

  • Sequence origins matter. The same listed values can receive different output indices if their first samples do not both occur at zero.
  • A full convolution is longer than either finite input in many cases; a cropped or same-length result represents only part of it.
  • Continuous plots show geometric overlap; for ordinary convolution integrals, changing a piecewise function only at isolated boundary points does not change the result.

Common questions

Why is the kernel shown backward?

Kernel reversal is part of convolution itself. In the discrete formula h[n-k], increasing k reads the kernel in the opposite direction before the shift is applied. If the kernel is not reversed, the sliding product computes cross-correlation instead. The two results can still match when the kernel is symmetric.

Does convolution always make a signal smoother?

No. A normalized averaging kernel can smooth rapid changes, but convolution is not inherently a smoothing operation. Difference kernels can emphasize changes, an impulse can preserve the signal, and other kernels can introduce shifts or oscillatory responses. The displayed result depends on the kernel values, their indexing, and how they overlap the signal.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

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