A short guide to direct colouring

Since Xyrus-02 introduced direct colouring as a default feature in 7X.14, the facility has been available for any Apophysis artists keeping up with the 7X series. There seems, however, to be a fairly widespread confusion over what it is and how to use it.

It helps initially to understand how a normal flame fractal is coloured. Each variation effectively possesses a coordinate system that makes a contribution to the overall structure of the flame, and the colouring follows this structure. However, we can also consider separating that coordinate system from the structure and applying it directly to the gradient. Taking linear as the trivial example, the gradient in mapped by the coordinate system of the variation, and so appears in pure form as a series of vertical coloured stripes across the flame structure, just as the gradient appears on its tab. That would in itself be boring. Except we can blend the 2 colouring modes and so obtain effects never previously possible with flames. Strictly speaking, direct colouring isn't part of a true flame fractal, but I think we needn't worry too much about purism Bubble maps the gradient to its coordinate system to give concentric rings of colour. And any final xform distorts the colouring as it distorts the structure.

In summary, you could say that the  (direct part of the) colouring is structure-independent.

Direct colouring is simply implemented: by default, all transforms of new/legacy flames are assigned a DC coefficient of 1 (on the Colors tab of the Editor), and any DC variation used will implement the colouring fully. Reducing the DC coefficient blends the two modes pro rata.

Further to the basics, we'll consider the current three main DC variations: dc_bubble; dc_linear; and julian2dc. when combined within a transform, a hierarchy emerges:

julian2dc > dc_linear > dc_bubble

When used in separate transforms, the effects overlay.

The three also possess variables:

dc_bubble_centerx - x-offset for pattern centre
dc_bubble_centery - y-offset for pattern centre
dc_bubble_scale - effectively an inverse frequency: a value of 0.1 means that the ring pattern repeats 10 times

dc_linear_offset - effectively rotates the gradient, full scale 2
dc_linear_angle - tilts the gradient, measured in radians
dc_linear_scale - as for dc_bubble, effectively an inverse frequency: a value of 0.1 means that the line pattern repeats 10 times

julian2dc_col - spirals the colour rays and introduces a discontinuity. Advanced tip - the discontinuity may be eliminated by using a symmetrical gradient with integer variable value.