How does the Replace Below tool work in Aspire, and what are its replacement options?

Overview

Applies to: Aspire 12.5 only. Replace Below is not in the VCarve Pro manual.

Replace Below (the form's full name is "Replace Values Below Z with Plane") trims or flattens the bottom off a component. It solves a common problem: you have a baked component where a foreground element sits on top of a background layer, and you want to remove or change what is underneath without rebuilding the whole model. It removes everything below a chosen height and, optionally, drops the model by that height.

The Problem It Solves

Example: a grapevine clipart component baked on top of a textured background. Once baked together, the two elements are merged into one heightmap. Replace Below lets you remove what is underneath a threshold height.

Other use cases:

• Remove a texture or background from under a relief clipart after baking
• Strip out a base platform from underneath a 3D component
• Clean up the bottom of an imported STL that has an unwanted base plate or extra thickness from a 3D scan
• Remove an unwanted negative part of a component (from sculpting, or from combining with a deep subtracted model)
• Reset the bottom of a component to zero so it sits cleanly on the modeling plane

How to Access It

Two ways:

• Modeling tab: the Replace Below icon in the editing row
• Model menu: Replace Below

Select one or more components first, or activate a level to work on all the visible components beneath it.

The Replace Value Below Threshold

Before choosing a replacement, you enter the Replace Value Below height, the height at which the cut happens:

• Everything below this height gets replaced
• Everything above it is left unchanged

Local height: the value is local to the selected component(s). It is the value you would see if you hid everything except the components of interest, which is why it is easier to apply this to levels.

How to find the right value:

• If you know the thickness of the layer you want to remove (for example the background texture is 0.28"), enter that value directly
• In the 3D view, the form shows a moveable plane with a blue central pin. Click and drag the pin up or down to the height where everything below it should be replaced
• Or try a value and adjust, using Undo (Ctrl+Z) until only the background is removed

The Replacement Options

Replace Value With offers two choices, and a separate checkbox controls whether the model drops.

Plane

Replaces everything below the threshold with a flat plane at the threshold height.

Result: The component has a clean flat bottom at the specified height, and the foreground element sits above a flat base.

Use for: When you want the component to have a defined flat base. A flat base gives 3D finishing toolpaths a clean floor.

Transparent

Replaces everything below the threshold with transparency, completely removing the heightmap data below the threshold.

Result: The component loses its base. The foreground element exists alone with no background behind it.

Use for: When you baked a foreground element onto a background and want to recover just the foreground element. This is the closest thing to an "undo the bake" option.

Lower Component by Value (checkbox)

When checked, the model is also dropped by the given height. This is useful when the model is too thick or you want to get rid of a background that came in with an STL model. The flat bottom ends up at zero instead of at the threshold height. If you set the value to 0, it removes everything below the zero plane.

The Options at a Glance

Selecting Multiple Components

If only a single component is selected, it is replaced by the result. If you select multiple components (or a level with more than one component), they are baked into a single component first, and the operation is applied to that baked component. If you want different settings per component, apply the tool to them one at a time.

Measuring the Right Height

Three methods:

1. Know it in advance: if you created the background component, you know its height (for example you set a texture to 0.28" height)
2. Drag the pin: use the moveable plane with the blue pin in the 3D view
3. Hover in the 3D view: move the cursor over the background area and read the height at the bottom of the screen