Models
Models are files that contains 3d objects like characters, objects, and all kind of elements. Evergine supports importing models created by 3D editing software (like 3ds Max, Blender or CAD software like Solidworks.) but also supports procedural model generation.
Models are crucial assets in every graphical application because can provide high quality and realism.
In Evergine a Model is a graphical element that combines multiple parts to conform a full 3D object in a scene.
It can contains the following parts:
- Node Hierarchy.
- MeshContainers
- Material references.
- Skinning information.
- Animation Clips
Node Hierarchy
A Model contains a node graph that covers all the objects of the 3d model. They are covered in the NodeContent class. They can have geometry or just serve as dummy element, but all of them contains a transform information (position, orientation and scale) and a list of children.
Model contains the hierarchy in these two properties:
| Property | Description |
|---|---|
| AllNodes | The list of all the NodeContents, whether they are in the root level or not. |
| RootNodes | The indices of the NodeContent elements of the AllNodes list that contains the nodes at root level (they don't have a parent). |
For example, if we have this node hierarchy:
A Model would have them stored in this way:
NodeContent
The NodeContent refers to the class that represents one node. It contains the basic information of a node of a 3d model:
| Property | Description |
|---|---|
| Name | Name of the node |
| Children | Array of the NodeContent children of the node. |
| Translation | Local Vector3 translation of the node. |
| Orientation | Local Quaternion orientation of the node. |
| Scale | Local Vector3 scale of the node. |
| Mesh | MeshContainer reference of the node. That means the node has geometry attached to it. null if the node doesn't have geometry. |
| Skin | Reference of a SkinContent element, meaning the node is a skinned mesh. null if the node is not skinned. |
MeshesContainers
In a Model mesh containers are where the 3d geometry is stored. It usually represents one full object, and it can contains one or more Meshes (see this section for more information.). The main reason for the MeshContainer concept is that a geometry attached to a node can contain multiple sub-elements with a different material each of them. One MeshContainer can be referenced by one or more nodes, making the model more memory efficient.
| Property | Description |
|---|---|
| Name | Name of the mesh container. |
| Skin | Reference of the SkinContent for skinning information (if it's the case). |
| BoundingBox | The Bounding box of the mesh. |
| Meshes | List of the meshes of this container |
Materials
The model also contain a list of a tuple containing the material id and the material name referenced by its meshes. The Mesh class contains a parameter called MaterialIndex which tells us the index of this list we're refering to.
Skinning Information
Evergine supports Skinning animation. With this method a geometry is deformed following the transformations of a set of bones.
To support it the model class contains an array of SkinContent class, that represents the skinning information of a geometry. Every MeshContainer and Node that as a skinned mesh references one of the elements of the array.
The SkinContent class contain this information:
| Property | Description |
|---|---|
| Name | Name of the skinning content. |
| Nodes | Array of integer that contain the indices of the AllNodes list of the Model class. They are the bone nodes of the skeleton. |
| InverseBindPoses | Array of Matrix4x4. For every node of the skeleton there is a matrix in that contains the inverse bind pose relative to its parent. |
| RootJoint | Int that represents the index in the Nodes array of the root bone of the skinning. |
Using this properties animating the nodes referenced by this SkinContent will animate the geometry accordingly.
In order for the skinned mesh to work properly, the Vertex Buffer of the skinned mesh needs the following fields:
| Semantic | Type | Description |
|---|---|---|
| BoneIndices | ´int4short´ | Vector that contains the indices of the bones (from the Nodes list) affected by this vertex. |
| BoneWeights | float4 | For every bone from he previous field, the weight indicates the percentaje of the box transforms that applies to this vertex. |
Animations
In Evergine model animation is achieved by animating nodes. If those nodes are part of a skinning bones, it will also animate the skinned mesh accordingly.