Normal coloring algorithms return an index value that is looked up in the gradient to produce a color for each pixel. This enables you to easily change the colors by editing the gradient. On the other hand, it limits the colors that can appear in the layer to the colors available in the gradient.
Unlike normal coloring algorithms, direct coloring algorithms directly return a color for each pixel. They are more powerful because they can return any desired color, and perform sophisticated merging operations internally.
Direct coloring algorithms can access the gradient and use its colors, but they are not limited to those colors. Because of this flexibility, editing the gradient will cause the layer to be recalculated. You can still use the coloring settings (such as Color Density) to change the appearance of the gradient.
Note that because the coloring algorithm decides how the gradient is used, the resulting colors in the layer may or may not be directly related to the colors in the gradient.
You can tell when a direct coloring algorithm is selected in the Inside or Outside tab because the text "Direct coloring algorithm" is visible below the title.
An example of a direct coloring algorithm is Direct Orbit Traps.
Next: Standard coloring algorithms
Working with coloring algorithms