core.points (procNode)

Points made from columns: a count of points, each attribute given as a column, a field or a constant.

Built from the make kernel (SHAPE = "points") for the elements and a point-class write for every entry of columns. The call is g.core.points({ columns = { P = positions, mass = 1.0 }, count = 64 }); count is how many points there are. The elements are made on the device.

Inputs

• columns (Record, optional). The attributes, by name: each a column of the point count, a field evaluated over the points, or a constant. P places the points; the other names are carried as point attributes.
• count (Float). Default 0. At least 0. How many points.

What a column takes

Each entry of columns is a field, a Column, a constant, or a list with one entry per point (the table below states every form):

• A field evaluated over the points, such as vector.create(g.element.id * 2, 0, 0) or g.field.noise({ position = g.element.P }): every point takes the field's value at its own element number.
• A Column with one element per point: a column another node answers (g.attribute.read, a column of core.entity.read), g.core.column({ values = { ... }, type = "Float" }) for numbers given in the graph, or g.op.transfer.upload({ values = { P = { type = "Vec3", values = { x0, y0, z0, x1, y1, z1, ... } } } }).P for vectors given in the graph, their components laid flat.
• A constant every point takes: a number (a Float column) or a vector made by vector.create (a Vec2, Vec3 or Vec4 column).

Without a P entry the points lie in a row along x from 0 to 1, where core.make places them.

What a column entry can be

Entry	Becomes
a field (g.math.vec3(g.element.id * 5, 0, 0), g.element.id % 2)	evaluated over the points: one value each
a Column of the point count	the column as it is
a list of vectors, one per point ({ vector.create(0, 0, 0), vector.create(5, 0, 0) }, or { x, y, z } records)	a numeric Vec2, Vec3 or Vec4 column, one vector per point, every vector of the list one width
a list of texts or records, one per point ({ "oak", "pine" })	a column of those values, one per point
a number, a vector, a text or a record	that value at every point
a list of numbers ({ 0, 1, 0 })	one vector, at every point

A list of vectors, texts or records holds exactly one entry per point; any other length is refused. A number that differs per point is a field or a Column: a list of numbers is read as one vector, so { 1, 2, 3 } over three points gives every point the vector (1, 2, 3).

Outputs

• points: the points, count of them, carrying P and every column of columns.

Example

local points = g.core.points({ count = 3, columns = { P = vector.create(g.element.id * 2, 0, 0), mass = 1.5 } })

The three points stand at x = 0, 2 and 4, each with mass 1.5. Positions given as numbers in the graph go through an upload:

local where = g.op.transfer.upload({ values = { P = { type = "Vec3", values = { 0, 0, 0, 1, 0, 0, 3, 0, 0 } } } }).P
local points = g.core.points({ count = 3, columns = { P = where } })