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package pixel
import "image/color"
// Target is something that can be drawn onto, such as a window, a canvas, and so on.
// You can notice, that there are no "drawing" methods in a Target. That's because all drawing
// happens indirectly through Triangles and Picture instances generated via MakeTriangles and
// MakePicture method.
type Target interface {
// MakeTriangles generates a specialized copy of the provided Triangles.
// When calling Draw method on the returned TargetTriangles, the TargetTriangles will be
// drawn onto the Target that generated them.
// Note, that not every Target has to recognize all possible types of Triangles. Some may
// only recognize TrianglesPosition and TrianglesColor and ignore all other properties (if
// present) when making new TargetTriangles. This varies from Target to Target.
MakeTriangles(Triangles) TargetTriangles
// MakePicture generates a specialized copy of the provided Picture.
// When calling Draw method on the returned TargetPicture, the TargetPicture will be drawn
// onto the Target that generated it together with the TargetTriangles supplied to the Draw
// method.
MakePicture(Picture) TargetPicture
// BasicTarget is a Target with additional basic adjustment methods.
type BasicTarget interface {
// SetMatrix sets a Matrix that every point will be projected by.
// SetColorMask sets a color that will be multiplied with the TrianglesColor property of all
// Triangles.
// Triangles represents a list of vertices, where each three vertices form a triangle. (First,
// second and third is the first triangle, fourth, fifth and sixth is the second triangle, etc.)
type Triangles interface {
// Len returns the number of vertices. The number of triangles is the number of vertices
// divided by 3.
Len() int
// SetLen resizes Triangles to len vertices. If Triangles B were obtained by calling Slice
// method on Triangles A, the relationship between A and B is undefined after calling SetLen
// on either one of them.
SetLen(len int)
// Slice returns a sub-Triangles of this Triangles, covering vertices in range [i, j).
// If Triangles B were obtained by calling Slice(4, 9) on Triangles A, then A and B must
// share the same underlying data. Modifying B must change the contents of A in range
// [4, 9). The vertex with index 0 at B is the vertex with index 4 in A, and so on.
// Returned Triangles must have the same underlying type.
Slice(i, j int) Triangles
// Update copies vertex properties from the supplied Triangles into this Triangles.
// Properies not supported by these Triangles should be ignored. Properties not supported by
// the supplied Triangles should be left untouched.
// The two Triangles must have the same Len.
// Copy creates an exact independent copy of this Triangles (with the same underlying type).
Copy() Triangles
// TargetTriangles are Triangles generated by a Target with MakeTriangles method. They can be drawn
// onto that (no other) Target.
type TargetTriangles interface {
// Draw draws Triangles onto an associated Target.
// TrianglesPosition specifies Triangles with Position property.
type TrianglesPosition interface {
Position(i int) Vec
// TrianglesColor specifies Triangles with Color property.
type TrianglesColor interface {
Color(i int) RGBA
// TrianglesPicture specifies Triangles with Picture propery.
// The first value returned from Picture method is Picture coordinates. The second one specifies the
// weight of the Picture. Value of 0 means, that Picture should be completely ignored, 1 means that
// is should be fully included and anything in between means anything in between.
type TrianglesPicture interface {
Picture(i int) (pic Vec, intensity float64)
// Picture represents a rectangular area of raster data, such as a color. It has Bounds which
// specify the rectangle where data is located.
type Picture interface {
// Bounds returns the rectangle of the Picture. All data is located witih this rectangle.
// Querying properties outside the rectangle should return default value of that property.
Bounds() Rect
// TargetPicture is a Picture generated by a Target using MakePicture method. This Picture can be drawn onto
// that (no other) Target together with a TargetTriangles generated by the same Target.
// The TargetTriangles specify where, shape and how the Picture should be drawn.
type TargetPicture interface {
// Draw draws the supplied TargetTriangles (which must be generated by the same Target as
// this TargetPicture) with this TargetPicture. The TargetTriangles should utilize the data
// from this TargetPicture in some way.
// PictureColor specifies Picture with Color property, so that every position inside the Picture's
// Bounds has a color.
// Positions outside the Picture's Bounds must return full transparent (Alpha(0)).
type PictureColor interface {
Color(at Vec) RGBA
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