Face

Structures and linked data definitions for faces

The Face array defines the list of faces for the mesh. Each face defines a material index, which gives the face its color properties based on material defined from the material list. Faces are all trianges and define a, b, c indices from the vertex list for the position.

Each vertex can additionally be provided with color, normals and uv. The reason that these are defined here and not in the vertex list, is because the vertex list is intended to be a unique list of positions associated with weight. The attributes of color, normals, and uv define properties of a face-per-point. And as such were included in the face definition for the purposes of defining an interchange format.

In the case of a delivery format, these properties would be declared in the vertex list.

JSON

Format

{
  "material": 0,
  "a": {
    "index": 0,
    "color": "rgb(255, 255, 255)",
    "normal": [0, 0, 0],
    "uv": [0, 0]
  },
  "b": {
    "index": 0,
    "color": "rgb(255, 255, 255)",
    "normal": [0, 0, 0],
    "uv": [0, 0]
  },
  "c": {
    "index": 0,
    "color": "rgb(255, 255, 255)",
    "normal": [0, 0, 0],
    "uv": [0, 0]
  }
}

Type

type DashPoint = {
  index: number;
  color: string | undefined;
  normal: number[],
  uv: number[] | undefined;
}

type DashFace = {
  material: number;
  a: DashPoint;
  b: DashPoint;
  c: DashPoint;
}

Fields

material

The index of the material to use for the face.

a

The a point for the triangular face

b

The b point for the triangular face

c

The c point for the triangular face

index

The index of the vertex from the vertex list which describes the position for the point.

normal

The normal value for the vertex as a vec3.

color

The color for the vertex as an 8 byte rgba value.

uv

The diffuse texture mapping for the vertex as vec2. A texture must be assigned to the material for the face to this to have any effect.

Binary

Struct

typedef struct {
  uint32_t index;
  uint8_t color[4];
  float normal[3];
  float uv[2];
} DashPoint;

typedef struct {
  uint32_t index;
  uint32_t material;
  DashPoint a;
  DashPoint b;
  DashPoint c;
} DashFace;

Table

Offset	0x00	0x04	0x08	0x0c
0x0000	index	material	a.index	a.color
0x0010	a.normal[0]	a.normal[1]	a.normal[2]	a.uv[0]
0x0020	a.uv[1]	b.index	b.color	b.normal[0]
0x0030	b.normal[1]	b.normal[2]	b.uv[0]	b.uv[1]
0x0040	c.index	c.color	c.normal[0]	c.normal[1]
0x0050	c.normal[2]	c.uv[0]	c.uv[1]

Fields

index

The index of the face in the array starting from zero.

material

The index of the material to use for the face.

a

The a point for the triangular face

b

The b point for the triangular face

c

The c point for the triangular face

index

The index of the vertex from the vertex list which describes the position for the point.

normal

The normal value for the vertex as a vec3.

color

The color for the vertex as an 8 byte rgba value.

uv

The diffuse texture mapping for the vertex as vec2. A texture must be assigned to the material for the face to this to have any effect.

Limiations

• Should we be using { x, y, z } and { u, v } structs?

• We have a nop at the end of the face struct

• Should we move normals, color and uv to the vertex definition?

• Do we want to allow for nested types in our definition?