Common HueForge Terms

Blending Down

This is the traditional way of using HueForge. Darker colors on the bottom with the lighter colors on the top. Your blending is always referencing the colors below the current layer. The benefit of this mode is that darker colors tend to have lower #Transmission Distance (TD) and do not blend well, where brighter colors are available in higher TDs and can be blended providing shadows. This makes the filament requirements for blending much simpler. The drawback is primarily in modes like Color Pop and Color Aware. Since each section is it's own HueForge, the top of each section often has a white which will show on the edges of the print below the black of the next section.

Blending Up

In #Standard Luminance mode, filaments are blended "down" to darker base layers (most commonly black). Blending up reverses this and puts the lighter colors at the bottom and the darker color at the top. This generally requires either a high TD dark shade, or multiple shades of a color to allow smooth color blending. The benefit is the black layer is generally shared with the next section and there will not be any white lip around the base of the next layer (see [Rebasing]). Blending up is common in #Color Match but can also be used in #Color Pop and #Color Aware using #Split Image or #Invert Region

Color Aware

Color Aware is a #Luminance Mode that splits the HueForge mesh into 3 sections by "color". (See Color_Aware for a basic How To guide) The colors are defined by the RGB color channels red, green, and blue. Color is picked by which color channel has the maximum value. Ties go to red, and if #Tolerance is 0, grayscale will go into blue unless there is a #Color Shift. This lets users separate color regions in images by color though sometimes the groupings are not ideal for the image. For instance yellow is in the red bucket, but often conflicts with skin tones or needs to blend smoothly with greens for leaves/plants. Using the CA Presets can also allow users to effectively remove one of the three ranges from the image when your image is primarily just two colors, though this is currently a byproduct of applying specific settings and is not a true removal of the third color space.

Color Core

The color core, in the middle of the HueForge display, is a visual representation of each layer in a HueForge print and how they blend. This reference will show in real-time the way moving color sliders will affect the colors of various layers in the mesh. In v0.8.0 (currently Beta only) the Color Core gains slider flags which allow direct manipulation of the sliders on the Color Core and the ability to drop a color at a specific layer instead of just on a new slider.

Color Match

Currently in Beta release (Commercial License holders only), Color Match effectively lets users create their own "Luminance" function that is defined by color. When Color Match is selected, a new Color Core (called the Mesh Core) will be created. If this is the first time, the filaments on the Color Core will be copied onto the Mesh Core.

Toggling #Shown Colors will switch which Core is being used to predict mesh visualization (the left side image). This allows a user to use the Mesh Core to create a custom luminance stack by placing colors on the mesh core (either filaments or colors pulled from the image itself using Ctrl+Left-Click and Drag (or Command+Left-Click on MacOS - you must release Cmd after the drag has started to allow dropping)). HueForge will then go pixel-by-pixel and find the best color match on the Mesh Core and make that pixel location the correct height to show that color when printed. This process will build a mesh that can then be colored by switching Shown Colors to the Color Core and applying Filaments. It is not recommended to apply #Image Colors to the Color Core since they do not represent real filaments and you will not be able to print with them.

Color Match allows for many more "Color Bins" than #Color Aware but it can still be difficult to distinguish all colors. Highlights in particular often bleed between color regions on the Mesh Core. Also the user should be aware that human color perception is extremely contextual and if you are having a hard time making a color match with filaments, you should grab the #Image Color and you will often be surprised by what the actual color is.

In Color Match, the #Combo Slider allows the user to add an upward or downward weighing on color matching. Values above 0.5 will weight matching upwards in the Mesh Core, and values below 0.5 will weight them downwards. This weighting is for all colors.

Color Pop

(Set Color Pop for a basic How To guide) The #Luminance Mode splits the image into two regions. One is defined as Grayscale and the other as Color. Grayscale is defined by setting the #Tolerance and the location of the split is defined by the #Combo Slider on the far right of the Model Geometry Dock. There are currently some bugs related to the split location indicator and you may need to move it up and down to get the display to properly reset.

A typical Color Pop image is mostly black and white with small, concentrated regions of often just a single color. These images are impossible to recreate in #Standard Luminance because the grayscale covers the entire luminance scale, and the color is necessarily in the middle of that same scale so your midtone grays become shades of the desired color along with the color regions.

To combat this, HueForge identifies grayscale regions and color regions and turns them into two separate luminance regions stacked on top of each other. You are then free to blend them separately. But it is highly recommended that you #Rebase the upper region.

Color Shift

Color Shifting is available in #Color Match and #Color Aware as a spin box next to the color box icons. It allows for adding or subtracting values globally from a given color channel in the image. This can be very useful for moving colors which straddle the border of two color bins into just one of them. A yellow that alternates between red and green for instance. Also commonly Black and White need color shifting to settle into a single bin. This can also be used to shift grayscale (at 0 #Tolerance) into either the red or green color bins from the default blue.

Some images benefit more from localized color shifting in an image editor to bring small regions of the image fully into a specific bin. This is currently outside the scope of HueForge.

Combo Slider

The far right hand side of the Model Geometry dock has an enigmatic slider. This slider originally had a single function. In #Combo Luminance, it allows for weighted mixing between #Standard Luminance and #Max Channel Luminance modes. This was very useful when there weren't any color sensitive luminance modes, but is not much used now. Since then, other #Luminance Modes also make use of this slider. Specifically #Color Pop and #Color Match make use of it.

Invert Region

(v0.8.0 Beta only) In Color Aware, you can right click on one of the color regions next to the Color Core and choose "Invert Region" which will flip the order of the mesh for that color region and show this on the region indicator as well. This can be used to smooth the blending between regions.

Lazy Programmer Rectangle (LPR)

The LPR is an artifact of the #Mesh model that appears in the slicer when the outer background of the original image is defined to be transparent. Because it has no height, it disappears when the model is sliced. Someday the programmer will get around to slicing the background away before the model is stored.

Luminance Modes

HueForge currently supports these Luminance Modes #Standard Luminance #Max Channel Luminance #Combo Luminance Scaled Max Channel Luminance #Color Aware #Color Pop #Color Match (Beta Only)

Max Channel Luminance

A simplified luminance value which looks at the value of only one color channel, the channel with the maximum value, and uses it to set the luminance with the function Channel Value/255.0.

Mesh

HueForge generates a triangular mesh based on the source image and Luminance function. That mesh is displayed to the left of the source image (in the middle of the screen most of the time). You can rotate and move the mesh or turn on the Wireframe mode to see the triangles that make it up. This mesh is manipulated by quite a few controls and updates in real-time and is used to create the color prediction. The image generated part of the mesh starts at Min Depth and goes to Actual Depth which is constrained by Max Depth (it can be a layer taller than Max Depth in some situations). Anything below Min Depth is solid, though you can still blend colors in the Min Depth region.

Max Depth

This is the maximum height specified for the geometry #Mesh. The actual depth of the mesh is specified by the highest slider and can be less when Dynamic Depth is selected. The mesh is made equal Max Depth when Static Depth or Clipped Depth is selected. Note that the blending layers extend from the #Min Depth to the Max Depth values.

Min Depth

This is the minimum height at which the geometry #Mesh where color blending begins.

Rebasing

The process of adding a new black (or other dark color) midway up the Color Core in modes like #Color Pop or #Color Aware at the start of the next region to bring back shadows and depth to the next region.

Split Image

In #Color Pop for version 0.7.1 on and #Color Aware in version v0.7.x the Negative button in the General Options dock will turn into Split Image. This option will negate the bottom most region of the mesh (grayscale by default for Color Pop and Blue by default for Color Aware) and make it inverted in color order.

Standard Luminance

The standard luminance model is a visual model which attempts to map colors to human perceptions of brightness. This is the model use for making lithophanes and as such was the first model used to build HueForge meshes. The default HueForge Luminance mode is #Combo Luminance which is a mixture between Standard Luminance and #Max Channel Luminance but with the weight set to 100% Standard Luminance on the #Combo Slider. In this mode, colors with overlapping luminance values will be impossible to separate, but if your image is shades of the same colors (fire for instance) or grayscale, it will work beautifully. There are still a large number of images which work well in Standard mode.

Transmission Distance (TD)

A measurement in millimeters of how thick a solid block of filament needs to be to block 95%+ of light from passing through. This is also referred to commonly as TD. This measurement is fundamental to how HueForge calculates how filaments blend.

Tolerance

Strict Grayscale is defined by colors with exactly the same values in their RGB channels. However in practice, many "grayscale" images are color shifted slightly to be warmer or cooler as the subject matter warrants. As a result, in modes like #Color Pop, it can be hard for HueForge to correctly separate Grayscale from Color. To allow this, HueForge has a Tolerance slider. This slider allows the user to expand the definition of Grayscale to include more colors. The tolerance number is the amount of counts the individual color channels can differ. In general this should be as low as possible while still separating the grayscale from color. In #Color Pop, your tolerance value will often be in the range of 10-50 and uncommonly be as high as 90. A value of 0 in #Color Pop is strict Grayscale with 0 deviation allowed between channels. If you have desaturated your image in an image application, 0 often works very well. If you raise the tolerance level too high, the image will revert to #Standard Luminance but in a compressed area because all color will be treated as grayscale.

In #Color Aware, a Tolerance of 0 will not check for Grayscale at all. In #Color Aware, the goal is 0 tolerance, though some images will need a very low tolerance to separate the black and white into the bottom and top color regions respectively. In #Color Aware, Grayscale is spread through the entire vertical color stack and a non-zero tolerance often leads to colors showing up in unexpected locations in the image.