display.newMesh()

Type Function
Library display.*
Return value ShapeObject
Revision 2017.3151
Keywords shape, mesh, vector object
See also Shapes — Paths, Fills, Strokes (guide)
Display Objects (guide)

Overview

Draws a mesh shape by providing vertices of the shape. The local origin is at the center of the mesh and the anchor point is initialized to this local origin.

Syntax

display.newMesh( [parent,] [x, y,] options )

display.newMesh( options )
parent (optional)

GroupObject. An optional display group in which to insert the mesh.

x / y (optional)

Numbers. The location of the object relative to its parent.

options (required)

Table. Table containing options for the mesh — see the next section for details.

Options Reference

The options table accepts the following parameters for the mesh:

vertices (required)

Array. An array of x and y coordinates of vertices forming the mesh. Meshes are built with these vertices depending on the mode parameter.

parent (optional)

GroupObject. An optional display group in which to insert the mesh. If included here, this will override any parent definition specified outside of the options table.

x / y (optional)

Numbers. The location of the object relative to its parent. If included here, these will override any x or y definitions specified outside of the options table.

mode (optional)

String. String indicating how the mesh should be formed with the provided vertices. Default is "triangles". Acceptable values are "triangles", "strip", "fan", or "indexed". See Mesh Draw Modes below for a description of each mode.

indices (optional)

Array. An array of indices required for mode type of "indexed". For example, to mimic the behavior of the "fan" mode, the value of this parameter could be { 1,2,3, 2,3,4, 3,4,5 }.

zeroBasedIndices (optional)

Boolean. Convenience parameter with default of false. If set to true, the indices array will be treated as a zero-based array.

uvs (optional)

Array. An array of u and v texture coordinates of vertices forming the mesh. If omitted or invalid, UVs will be automatically assigned based on normalized vertices values. Texture coordinates are normalized coordinates where 0,0 is the top-left corner of the image and 1,1 is the bottom-right corner of the image.

Mesh Draw Modes

triangles/indexed

Meshes with a mode of "triangles" or "indexed" are formed with disjointed groups of three consecutive vertices. An example of a "triangles" mode could have vertices with indices 1,2,3, 4,5,6, and 7,8,9. Note, however, that the "triangles" mode may result in duplicate vertices shared by several triangles — to avoid this, you can use the "indexed" type and define an indices table with indices pointing to the vertices used.

While these methods can be used to encode any mesh, they both have some duplication if a vertex is used by several triangles. In the case of "triangles", this is the vertices themselves. In the case of "indexed", this is the vertex indices. Duplicating indices is much cheaper because they're single integer numbers, not an entire vertex with coordinates and texture coordinates.

In some cases, this duplication can be avoided via the "strip" or "fan" mode (see below).

strip

Meshes with a mode of "strip" are formed with three consecutive vertices. An example could have vertices with indices 1,2,3, 2,3,4, and 3,4,5. For more information on this type, see here.

fan

Meshes with a mode of "fan" are formed with an initial vertex and two ending vertices. An example could have vertices with indices 1,2,3, 1,3,4, and 1,4,5. For more information on this type, see here.

Gotchas

Methods

(Inherits properties from ShapeObject)

Shape objects have a path property that exposes methods to manipulate the mesh. Most methods accept the index parameter which is the Lua array index of the vertex in question (the first vertex would have an index of 1). All arguments are numbers.

object.path:setVertex()

Sets the vertex with index index to coordinates x and y:

object.path:setVertex( index, x, y )
object.path:getVertex()

Returns two numbers corresponding to a vertex's coordinates:

object.path:getVertex( index )
object.path:setUV()

Sets the vertex with index index to texture coordinates u and v:

object.path:setUV( index, u, v )
object.path:getUV()

Returns two numbers corresponding to a vertex's texture coordinates:

object.path:getUV( index )
object.path:getVertexOffset()

Returns two numbers corresponding to the horizontal and vertical offsets applied when moving the origin to the center of the mesh. You can offset the mesh object by these values to compensate for initial shift and get precise vertex positions in world coordinates.

object.path:getVertexOffset()

Note that a vertex with coordinates x and y will have world coordinates of mesh.x + x - offsetX and mesh.y + y - offsetY respectively, assuming no scaling is applied. Consider the following command which shifts the object by the offsets and puts a vertex at 0,0 into the previous object origin:

mesh:translate( mesh.path:getVertexOffset() )

Examples

Triangles Mode
local mesh = display.newMesh(
    {
        x = 100,
        y = 100,
        mode = "triangles",
        vertices = {
            0,0, 50,0, 0,100,
            0,100, 50,0, 100,100,
            100,100, 50,0, 100,0
        },
        uvs = {
            0,0, 0.5,0, 0,1,
            0,1, 0.5,0, 1,1,
            1,1, 0.5,0, 1,0
        }
    })
mesh:translate( mesh.path:getVertexOffset() )  -- Translate mesh so that vertices have proper world coordinates

mesh.fill = { type="image", filename="cat.png" }

local vertexX, vertexY = mesh.path:getVertex( 3 )
mesh.path:setVertex( 3, vertexX, vertexY-10 )
Indexed Mode
local mesh = display.newMesh(
    {
        x = 100,
        y = 100,
        mode = "indexed",
        vertices = {
            0,0, 0,100, 50,0, 100,100, 100,0
        },
        indices = {
            1,2,3,
            2,3,4,
            3,4,5
        }
    })
mesh:translate( mesh.path:getVertexOffset() )  -- Translate mesh so that vertices have proper world coordinates

mesh.fill = { type="image", filename="cat.png" }

local vertexX, vertexY = mesh.path:getVertex( 3 )
mesh.path:setVertex( 3, vertexX, vertexY-10 )
Strip Mode
local mesh = display.newMesh(
    {
        x = 100,
        y = 100,
        mode = "strip",
        vertices = {
            0,0, 0,100,
            50,0, 100,100,
            100,0
        }
    })
mesh:translate( mesh.path:getVertexOffset() )  -- Translate mesh so that vertices have proper world coordinates

mesh.fill = { type="image", filename="cat.png" }

local vertexX, vertexY = mesh.path:getVertex( 3 )
mesh.path:setVertex( 3, vertexX, vertexY-10 )
Fan Mode
local mesh = display.newMesh(
    {
        x = 100,
        y = 100,
        mode = "fan",
        vertices = {
            50,0,
            0,0, 0,100, 100,100, 100,0
        }
    })
mesh:translate( mesh.path:getVertexOffset() )  -- Translate mesh so that vertices have proper world coordinates

mesh.fill = { type="image", filename="cat.png" }

local vertexX, vertexY = mesh.path:getVertex( 3 )
mesh.path:setVertex( 3, vertexX, vertexY-10 )