Mesh Class

Each surface of the mesh supports several morph targets.
Each surface has a quaternion-based tangent basis for the better loading speed.
8-bit vertex colors are supported.
Each vertex of a surface has 2 sets of indices: coordinate and triangle indices. It improves the loading speed and reduces data duplication.
Each vertex of a surface has 2 UV sets.
A bind pose transformation is stored for each mesh (even if there are no animations and animation frames). See also the getBoneTransforms() function.
Notice
The 1st animation frame should not contain the bind pose.

Vertex Data and Indices#

Each surface of the mesh consists of triangles, and each triangle has 3 vertices. Thus, for each mesh surface we have:

Total number of vertices = 3 * number of triangles.

If a vertex belongs to several triangles, we have to store several copies of such vertex. Each of these copies would store information about position, normal, binormal, tangent and texture coordinates. In order to reduce data duplication and increase loading speed UNIGINE uses the optimization described below.

There are 2 separate vertex data buffers are used:

CVertices coordinate buffer, which stores only vertex coordinates.
TVertices triangle buffer, which stores vertex attributes such as normal, binormal, tangent, color, UV coordinates.

On the picture below, arrows are used to show normals:

Surface that contains 2 adjacent triangles. Here C0...C3 are coordinate vertices, T0...T5 are triangle vertices

The coordinate buffer is an array of coordinate vertices. In order to reduce data duplication, vertices of surface which have the same coordinates are saved only once in the buffer. For example, the coordinate buffer for the surface presented on the picture above is the following:

Output

CB = [C0,C1,C2,C3]

Each polygon of the surface has 3 coordinates. We have 2 polygons, thus, we have 6 vertices, but we save in the CVertices buffer only 4, because 2 of them have the same coordinates. Each coordinate vertex contains coordinates (float[3]) of the vertex.

Notice

The number of vertices and coordinate vertices is the same.

The triangle buffer is an array of triangle vertices. For example, the triangle buffer for the surface presented on the picture above is the following:

Output

TB = [T0,T1,T2,T3,T4,T5]

Each triangle vertex can store:

Normal
Binormal
Tangent
1st UV map texture coordinates
2nd UV map texture coordinates
Color

Notice

The number of vertices and triangle vertices can be different.

The number of triangle vertices depends on the number of triangles, to which the vertex belongs. For example, if 2 triangles have 1 adjacent vertex with different normals for each triangle, 2 triangle vertices will be stored (the 1st and the 3rd vertices on the picture above). However, if the components are the same for all of the adjacent triangles, only 1 triangle vertex will be stored.

Both the coordinate and triangle vertices have indices. There are 2 index buffers to get proper cvertex and tvertex data for each vertex of each triangle of the mesh:

CIndices buffer — coordinate indices, which are links to CVertices data.
TIndices buffer — triangle indices, which are links to TVertices data.

The number of elements in these index buffers is equal to the total number of vertices of a mesh surface.

Coordinate Indices#

Each vertex of a mesh surface has a coordinate index - a number of the corresponding element of the coordinate buffer, where the data is stored. For the given surface the array of the coordinate indices is as follows:

Output

CIndices = [Ci0,Ci1,Ci3,Ci1,Ci2,Ci3]

Here:

The first 3 elements are the coordinate indices of the first (bottom) triangle.
The second 3 elements are the coordinate indices of the second (top) triangle.

Triangle Indices#

Each vertex of a mesh surface also has a triangle index - a number of the corresponding element of the triangle buffer, where the data is stored. For the given surface the array of the triangle indices is as follows:

Output

TIndices = [Ti0,Ti1,Ti5,Ti2,Ti3,Ti4]

Here:

The first 3 elements are the triangle indices of the first (bottom) triangle.
The second 3 elements are the triangle indices of the second (top) triangle.

Notice

The number of the coordinate and triangle indices is the same.

Obtaining Geometry from a Mesh-Based Object#

To get vertices from a mesh-based object (e.g. a static mesh, a skinned mesh and so on), you can do the following:

Create an instance of the Mesh class by using the create() method.
Copy geometry of the mesh-based object into this Mesh instance via the getMesh() method. The Mesh instance must be passed as a parameter to this method.
Get vertices of the Mesh.

Source code (C++)

// a mesh-based object from which geometry will be obtained
ObjectMeshStaticPtr staticMesh = ObjectMeshStatic::create("core/meshes/material_ball.mesh");
// create a new mesh
MeshPtr mesh = Mesh::create();
// copy geometry to the created mesh
if (staticMesh->getMesh(mesh)) {
	// get a vertex of the first mesh surface
	Math::vec3 vertex = mesh->getVertex(0,0);
} else {
	Log::error("Failed to copy a mesh\n");
}

Copying a Mesh into Another#

You can copy a mesh into another by using the Mesh class.

In the following example, we copy the ObjectMeshDynamic mesh to the new ObjectMeshDynamic class instance by using the Mesh class as a container. The executing sequence is the following:

It is supposed that you already have an ObjectMeshDynamic to copy. Create a Mesh class instance as a container for the ObjectMeshDynamic mesh.
Copy the ObjectMeshDynamic mesh into the Mesh by using the getMesh() function.
Create a new ObjecteMeshDynamic instance from the Mesh instance by using overloaded constructor of the ObjectMeshDynamic class.

Source code (C++)

/* ... */
// create ObjectMeshDynamic and Mesh instances
ObjectMeshDynamicPtr dynamicMesh = ObjectMeshDynamic::create();
MeshPtr firstMesh = Mesh::create();

// get the ObjectMeshDynamic and copy it to the Mesh class instance
dynamicMesh->getMesh (firstMesh);

// create a new ObjectMeshDynamic instance from the firstMesh mesh
ObjectMeshDynamicPtr dynamicMesh_2 = ObjectMeshDynamic::create(firstMesh);
/* ... */

Also you can copy the mesh by using the setMesh() function. For example, in the code below we set the mesh instance to the already created ObjectMeshDynamic mesh. The executing sequence is the following:

It is supposed that you already have 2 ObjectMeshDynamic class instances. Create the Mesh class instance as a container.
Copy the ObjectMeshDynamic to the Mesh by using the getMesh() function.
Set the mesh to the second ObjectMeshDynamic instance by using setMesh() function.

Source code (C++)

/* ... */
// create ObjectMeshDynamic instances 
ObjectMeshDynamicPtr dynamicMesh = ObjectMeshDynamic::create();
ObjectMeshDynamicPtr dynamicMesh_2 = ObjectMeshDynamic::create();

// create a Mesh instance
MeshPtr firstMesh = Mesh::create();

// get the mesh of the ObjectMeshDynamic and copy it to the Mesh class instance
dynamicMesh->getMesh(firstMesh);

// put the firstMesh mesh to the dynamicMesh_2 instance
dynamicMesh_2->setMesh(firstMesh);
/* ... */

NoticeYou can return the transformed mesh from the Mesh class to the same ObjectMeshDynamic instance without creating a new one, if necessary.

You can easily copy one mesh instance to a new one by using the constructor and pass the mesh instance as an argument:

Source code (C++)

MeshPtr firstMesh = Mesh::create();
MeshPtr secondMesh = Mesh::create(firstMesh);

Copying Mesh Surfaces#

By using the Mesh class you can copy surfaces from one mesh to another.

In the following example we create two meshes with different surfaces. The first mesh has the capsule surface, the second has the box surface. We copy the box surface from the second mesh to the first. The executing sequence is:

Create 2 instances of the Mesh class and add capsule and box surfaces to them.
Add the box surface from the second mesh (mesh_2) and add it to the first mesh (mesh_1) by using the addMeshSurface() function.
Create a new ObjectMeshDynamic mesh from the mesh_1 instance.
Add the dynamic mesh to the editor and set the material, property and name.

Source code (C++)

// create mesh instances
MeshPtr mesh_1 = Mesh::create();
MeshPtr mesh_2 = Mesh::create();

// add surfaces for the added meshes
mesh_1->addCapsuleSurface("capsule_surface", 1.0f, 2.0f, 200, 100);
mesh_2->addBoxSurface("box_surface", Math::vec3(2.2f));

// add the surface from the mesh_2 to the mesh_1 as a new surface
// with the name "new_box_surface"
mesh_1->addMeshSurface("new_box_surface", mesh_2, 0);

// create the ObjectMeshDynamic from the mesh_1 object
ObjectMeshDynamicPtr dynamicMesh = ObjectMeshDynamic::create(mesh_1);

// set the position of the mesh
dynamicMesh->setWorldTransform(translate(Math::Vec3(10.0f, 10.0f, 10.0f)));
// set the material to the mesh
dynamicMesh->setMaterial("mesh_base", "*");
// set the name of the mesh
dynamicMesh->setName("Dynamic Mesh");

NoticeYou can copy a surface from the source mesh and add it to the existing surface of the current mesh without creating a new one.

The ObjectMeshDynamic mesh will appear in the editor:

ObjectMeshDynamic with 2 surfaces

Adding Vertices and Changing Their Attributes#

The Mesh class allows adding vertices to a mesh and change vertex attributes.

In the following example, we create a plane by adding vertices to the mesh and change the attributes of some of these vertices. Let's clarify this:

Create the Mesh class instance and add 4 vertices to it.
Add 6 indices to create a plane.
After that tangents and normals are created by using the createTangents() and createNormals() functions.
The bounds of the mesh are updated to include all new vertices via the createBounds() function.
Current normal values of the 2 vertices are shown in console. After changing, new values are shown in console.
Tangent is shown in the console, and then it is changed and shown in the console again.
Create a new ObjectMeshDynamic mesh from the mesh instance.
Add the dynamic mesh to the editor and set the material, property and name.

Source code (C++)

// create a mesh instance
MeshPtr mesh = Mesh::create();

// add a new surface
mesh->addSurface("surface_0");

// add vertices of the plane
mesh->addVertex(Math::vec3(0.0f, 0.0f, 0.0f), 0);
mesh->addVertex(Math::vec3(0.0f, 0.0f, 1.0f), 0);
mesh->addVertex(Math::vec3(0.0f, 1.0f, 0.0f), 0);
mesh->addVertex(Math::vec3(0.0f, 1.0f, 1.0f), 0);

// add indices 
mesh->addIndex(0, 0);
mesh->addIndex(1, 0);
mesh->addIndex(2, 0);

mesh->addIndex(3, 0);
mesh->addIndex(2, 0);
mesh->addIndex(1, 0);

// create tangents
mesh->createTangents();

// create mesh bounds
mesh->createBounds(0);

// create normals
mesh->createNormals(0);

// get the normal vectors of the 1st and the 2nd normal before changing
Math::vec3 normal_0 = mesh->getNormal(0, 0, 0);
Math::vec3 normal_1 = mesh->getNormal(1, 0, 0);
// show the message in console about the normals
Log::message("the first normal is: %s: %0.1f %0.1f %0.1f and the second is: %s: %0.1f %0.1f %0.1f\n",
	typeid(normal_0).name(),
	normal_0.x,
	normal_0.y,
	normal_0.z,
	typeid(normal_1).name(),
	normal_1.x,
	normal_1.y,
	normal_1.z);

// set new normals values of the normals
mesh->setNormal(0, Math::vec3(1, 1, 0), 0, 0);
mesh->setNormal(1, Math::vec3(1, 1, 1), 0, 0);

// get the new normal vectors of the 1st and the 2nd normal
Math::vec3 new_normal_0 = mesh->getNormal(0, 0, 0);
Math::vec3 new_normal_1 = mesh->getNormal(1, 0, 0);
// show the new normals values in the console
Log::message("the first normal is: %s: %0.1f %0.1f %0.1f and the second is: %s: %0.1f %0.1f %0.1f\n",
	typeid(new_normal_0).name(),
	new_normal_0.x,
	new_normal_0.y,
	new_normal_0.z,
	typeid(new_normal_1).name(),
	new_normal_1.x,
	new_normal_1.y,
	new_normal_1.z);

// get the tangent value
Math::quat tangent = mesh->getTangent(0, 0, 0);
// show the tangent value in the console
Log::message("tangent is: %s: %0.1f %0.1f %0.1f %0.1f\n",
	typeid(tangent).name(),
	tangent.x,
	tangent.y,
	tangent.z,
	tangent.w);

// set the new value of the tangent
mesh->setTangent(0, Math::quat(0.0, -0.0, -0.0, 1), 0, 0);

// get the new tangent value
Math::quat new_tangent = mesh->getTangent(0, 0, 0);
// show the tangent value after changing
Log::message("tangent is: %s: %0.1f %0.1f %0.1f %0.1f\n",
	typeid(new_tangent).name(),
	new_tangent.x,
	new_tangent.y,
	new_tangent.z,
	new_tangent.w);

// create the ObjectMeshDynamic from the Mesh object
ObjectMeshDynamicPtr dynamicMesh = ObjectMeshDynamic::create(mesh);


// set the position of the mesh
dynamicMesh->setWorldTransform(translate(Math::Vec3(10.0f, 10.0f, 10.0f)));
// set the material to the mesh
dynamicMesh->setMaterial("mesh_base", "*");
// set the name of the mesh
dynamicMesh->setName("new_mesh");

When you launch the project, in the console you'll see the following:

Output

the first normal is: struct Unigine::Math::vec3: -1.0 0.0 0.0 and the second is: struct Unigine::Math::vec3: -1.0 0.0 0.0
the first normal is: struct Unigine::Math::vec3: 1.0 1.0 0.0 and the second is: struct Unigine::Math::vec3: 1.0 1.0 1.0
tangent is: struct Unigine::Math::quat: 0.5 -0.5 -0.5 0.5
tangent is: struct Unigine::Math::quat: 0.0 0.0 0.0 0.9

When setTangent() and setNormal() functions were called, the normal and the tangent changed their values.

Let's comment this part of the code:

Source code (C++)

// get the tangent value
Math::quat tangent = mesh->getTangent(0, 0, 0);
// show the tangent value in the console
Log::message("tangent is: %s: %0.1f %0.1f %0.1f %0.1f\n",
	typeid(tangent).name(),
	tangent.x,
	tangent.y,
	tangent.z,
	tangent.w);

// set the new value of the tangent
mesh->setTangent(0, Math::quat(0.0, -0.0, -0.0, 1), 0, 0);

// get the new tangent value
Math::quat new_tangent = mesh->getTangent(0, 0, 0);
// show the tangent value after changing
Log::message("tangent is: %s: %0.1f %0.1f %0.1f %0.1f\n",
	typeid(new_tangent).name(),
	new_tangent.x,
	new_tangent.y,
	new_tangent.z,
	new_tangent.w);

The result will be different. You can see what influence the tangent has on the vertex:


Plane with changed tangent	Plane with unchanged tangent

Adding a Surface to the Existing Mesh#

This section contains information on how to add a surface to the existing mesh.

In the following example, we add a surface to the existing mesh and then add necessary vertices and indices for the surface:

Create a new mesh instance from the file.
Add a new surface to the mesh.
Add vertices for the mesh surface.
Create indices for recently created vertices by using the createIndices() function.
Update the bounds of the mesh to include the created surface by using the createBounds() function.
Create a material to be assigned to the added surface.
Save mesh to the file and add it to the editor.

In the example, the box.mesh file has been taken from the UNIGINE SDK Samples. However, you can create a box mesh and save it to a file as follows:

Source code (C++)

// create an empty Mesh instance
MeshPtr box = Mesh::create();
// add a box surface to the Mesh 
box->addBoxSurface("surface_box", Math::vec3(1.0f));
// save the box to a file
box->save("unigine_project/meshes/box.mesh");

Source code (C++)

// load a mesh form the file
MeshPtr mesh = Mesh::create("unigine_project/meshes/box.mesh");

// add a new surface
mesh->addSurface("surface_triangle");

// add 3 vertices to the new surface
mesh->addVertex(Math::vec3(-0.5f, 0.5f, 0.5f), 1);
mesh->addVertex(Math::vec3(-0.5f, -0.5f, 0.5f), 1);
mesh->addVertex(Math::vec3(-0.5f, -0.5f, 1.5f), 1);

// create indices for the new surface
mesh->createIndices(1);
// create a new boundbox for the mesh including new surface
mesh->createBounds();

// save mesh to file
mesh->save("unigine_project/meshes/box_2.mesh");

// create ObjectMeshStatic from the Mesh object
ObjectMeshStaticPtr staticMesh = ObjectMeshStatic::create("unigine_project/meshes/box_2.mesh");


// prepare a material for the added surface:
// find the mesh_base material
MaterialPtr mesh_base = Materials::findMaterial("mesh_base");
// inherit a new material from it
MaterialPtr material = mesh_base->inherit("mesh_base_yellow", "unigine_project/materials/mesh_base_yellow.mat");
material->setParameter(Material::PARAMETER_COLOR, Math::vec4(255, 255, 0, 255));

// set the position of the mesh
staticMesh->setWorldTransform(translate(Math::Vec3(10.0f, 0.0f, 2.0f)));
// set the material to the mesh surfaces
staticMesh->setMaterial("mesh_base", 0);
staticMesh->setMaterial("mesh_base_yellow", 1);

The triangle surface added to the mesh:

Last update: 2019-12-25

Help improve this article

Was this article helpful?

Report a problem related to this article

(or select a word/phrase and press Ctrl+Enter)

Mesh Class

In This Article:

Vertex Data and Indices#

Coordinate Indices#

Triangle Indices#

See Also#

Obtaining Geometry from a Mesh-Based Object#

Copying a Mesh into Another#

Copying Mesh Surfaces#

Adding Vertices and Changing Their Attributes#

Adding a Surface to the Existing Mesh#