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Here's an explanation of my irregular bricks macro, so everyone
can have a chance to understand some of the magic that's at work
deep within it.
On 19 Jan 2000 10:15:35 -0500, Ron Parker wrote:
>#macro Irregular_Bricks( Brick, Mortar, MortarThick, Vary )
You probably already guessed this one, but I'll spell it out
just in case:
* Brick is a pigment that will be used to color the bricks.
* Mortar is a pigment that will be used to color the mortar.
* MortarThick is a number between 0 and 1, and it represents
the ratio of mortar to bricks.
* Vary is a nonnegative number that represents the maximum
deviation in the length of a brick from its nominal length
of 1 unit. If you specify .3, for example, the resulting
bricks will range in length from .7 units to 1.3 units.
The final pattern has rows of width 1 unit and bricks of average
length 1 unit. The regular rows are perpendicular to the Z axis.
The texture is designed to be applied to a planar surface parallel
to the XZ plane. You may scale and rotate appropriately.
> gradient z
> pigment_map {
This is the gradient that establishes the regular rows of
irregular bricks. Each interval of this gradient is a row
of bricks.
> [MortarThick Mortar]
The first part of a row of bricks is the mortar between rows.
That's what this piece of the map defines.
> [MortarThick gradient x
This piece of the map defines a row of bricks. Gradient x is
the basic pigment, but the stuff below mixes it up a bit.
> pigment_map {[MortarThick Mortar][MortarThick Brick]}
Each interval of this gradient consists of a bit of mortar and
a bit of brick.
> translate 1000*x
This gets us away from the origin, where the mortar would be
double-thickness due to the symmetry there. We could probably
also use a warp {repeat x} here to achieve the same effect
without prematurely sending our bozo textures to bad-noise-land.
> warp {turbulence Vary octaves 1}
Octaves 1 means "make only one step in a random direction of a
distance somewhere between zero and Vary." By itself, this would
tend to mix up the gradient a bit so it became wavy but not like
you normally expect from turbulence. In this macro, it has the
effect of moving the sample point a random distance in a random
direction, which is the primary factor in how random the bricks
are. This turbulence is also what's ultimately responsible for
the sections of wide and narrow mortar that appear some places,
but I don't know how to fix that.
> warp {planar z 0}
This forces the pigment to be an extrusion of what it looks like in
the x-y plane, something like a planar image map. In this macro, it
fixes the mortar lines so they're once again perfectly straight,
while leaving any turbulence-induced changes in the X and Y
directions intact. Remove it, and the mortar lines will be somewhat
wavy. a better way to achieve that, though, would be to apply light
turbulence to the texture as a whole once it's constructed.
> warp {reset_children}
This "turns off" the turbulence and the planar warp for the child
textures, which are the pigments you specified for the bricks and
the mortar. This ensures that the pigment on each brick looks like
you expected it to.
> ]
> }
> warp {repeat z offset 97.5*x}
This last warp has two effects. First, the repeat z fixes the
symmetry problem of the gradient pigment in the z direction.
Second, the offset 97.5*x causes POV to sample a different part
of the x-y plane for each row of bricks. If you look at a large
area of these bricks, you'll see that the brick pattern repeats
exactly 97.5 units away on adjacent rows. The .5 makes it so
that usually, bricks on adjacent rows don't begin and end at the
same spot. You could offset in y too, which would sample a
different pattern of bricks entirely and remove the repetition.
I didn't think of this when I originally wrote it.
>#end
--
These are my opinions. I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html
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