Polygon Meshes

dolphin-mesh.png

All visible game elements in a scene, whether it is a Model or a Shape, are made up of polygon meshes. JME3 has a com.jme3.scene.Mesh class that represents all meshes.

  • Meshes are made up of triangles: getTriangleCount(…) and getTriangle(…)

  • Each mesh has a unique ID: getId()

  • Meshes have transformations: Location (local translation), rotation, scale.

  • Meshes have a bounding volume. jME3 can detect intersections (that is, non-physical collisions) between meshes, or between meshes and 2D elements such as rays: collideWith().

  • Meshes are locked with setStatic() and unlocked with setDynamic().

    • Static Meshes cannot be modified, but are more optimized and faster (they can be precalculated).

    • Dynamic Meshes can be modified live, but are not optimized and slower.

You have several options when creating Geometries from meshes:

  • Use built-in Shapes as meshes;

  • Load 3D models (that is, meshes created in external applications); or

  • Create free-form custom meshes programmatically.

Vertex Buffer

The VertexBuffer contains a particular type of geometry data used by Meshes. Every VertexBuffer set on a Mesh is sent as an attribute to the vertex shader to be processed.

Mesh Vertex Buffers

Here is the list of VertexBuffer types.

Vertex Buffer Type Description

Type.Position

Position of the vertex (3 floats)

Type.Index

Specifies the index buffer, must contain integer data.

Type.TexCoord

Texture coordinate

Type.TexCoord2

Texture coordinate #2

Type.Normal

Normal vector, normalized.

Type.Tangent

Tangent vector, normalized.

Type.Binormal

Binormal vector, normalized.

Type.Color

Color and Alpha (4 floats)

Type.Size

The size of the point when using point buffers.

Type.InterleavedData

Specifies the source data for various vertex buffers when interleaving is used.

Type.BindPosePosition

Initial vertex position, used with animation.

Type.BindPoseNormal

Initial vertex normals, used with animation

Type.BoneWeight

Bone weights, used with animation

Type.BoneIndex

Bone indices, used with animation

Mesh Properties

Some Mesh properties from the Mesh class.

Mesh method Description

setBound(boundingVolume)

if you need to specify a custom optimized bounding volume

setStatic()

Locks the mesh so you cannot modify it anymore, thus optimizing its data (faster).

setDynamic()

Unlocks the mesh so you can modified it, but this will un-optimize the data (slower).

setMode(Mesh.Mode.Points)

Used to set mesh rendering modes, see below.

getId()

returns the Mesh ID, default value is -1

getTriangle(int,tri)

returns data of triangle number int into variable tri

scaleTextureCoordinates(Vector2f)

How the texture will be stretched over the whole mesh.

Mesh Rendering Modes

Here is the list of Mesh rendering modes.

Mesh Mode Description

Mesh.Mode.Points

Show only corner points (vertices) of mesh

Mesh.Mode.Lines

Show lines (edges) of mesh

Mesh.Mode.LineLoop

?

Mesh.Mode.LineStrip

?

Mesh.Mode.Triangles

?

Mesh.Mode.TriangleStrip

?

Mesh.Mode.TriangleFan

?

Mesh.Mode.Hybrid

?

Level of Detail

Optionally, custom meshes can have a LOD (level of detail optimization) that renders more or less detail, depending on the distance of the mesh from the camera. You have to specify several vertex buffers, one for each level of detail you want (very far away with few details, close up with all details, and something in the middle). Use setLodLevels(VertexBuffer[] lodLevels).