Convolve Matchbox

Convolve is a Matchbox shader dedicated to creating lens effects using an FFT-based convolution process.

The Convolve Matchbox shader requires a Front and a Kernel input to create the result. It then convolves the kernel with the pixels that you defined with the Qualifier controls. The kernel should be an image in the range of 256x256 pixels size. However, larger image can be used, at the cost of performance.

Highlights options restrict the convolve to the image highlights.

Threshold

Sets the colour value threshold over which a colour is considered a highlight.

Max Threshold

Sets the maximum colour value to be used as a highlight: values over this limit are not considered a highlight. Enabled by Enable Max Threshold.

Gain

Boosts or reduces the highlights selected by Threshold and Max Threshold.

Kernel options manage the kernel convolved with the highlights.

Scale

Reduces or enlarges the kernel by varying the size of the Kernel input. Note that the larger Kernel input, the longer the convolution process takes.

Rotation

Rotates the Kernel input.

Gain

Adds or removes gain from the Kernel input.

Tint

Changes the Kernel input colour.

Output options define what the Matchbox outputs.

Viewing

Selects what displays in the viewport the stages of the pipeline of the Convolve effect.

• Input: The Front input texture.
• Highlights: The result of the Highlights Controls. This result enhances the convolution process by allowing the creation of bokeh on image features that would otherwise not stand out.
• Kernel: The Kernel input as modified by the Scale and Rotation Kernel Controls. The resulting kernel, futher modified by the Gain and Tint controls, is what's being convolved.
• Convolution: The result of the convolution process.
• Result: The final result.

Additive Convolution

Enable to use only the Highlights result pass in the convolution process, and then add back onto the Front input using an additive blending. This allows for creative results similar to what PhysicalGlareSFX. Disable to convolve the kernel over the whole Front input and create a more natural result.

Mix

Controls the mix of the Result with the original source.

Normalize

Sets the Kernel energy to 1.0 before Kernel Gain and Tint are applied.