nanosg

NanoSG

Simple, minimal and header-only scene graph library for NanoRT.

NanoSG itself shoud be compiled with C++-03 compiler, but demo code uses C++11 features.

Build

Linux or macOS

premake5 gmake
make

Windows

premake5 vs2015

Data structure

Node

Node represents scene graph node. Tansformation node or Mesh(shape) node. Node is interpreted as transformation node when passing nullptr to Node class constructure.

Node can contain multiple children.

Scene

Scene contains root nodes and provides the method to find an intersection of nodes.

User defined data structure

Following are required in user application.

Mesh class

Current example code assumes mesh is all composed of triangle meshes.

Following method must be implemented for Scene::Traversal.

///
/// Get the geometric normal and the shading normal at `face_idx' th face.
///
template<typename T>
void GetNormal(T Ng[3], T Ns[3], const unsigned int face_idx, const T u, const T v) const;

Intersection class

Represents intersection(hit) information.

Transform

Transformation is done in the following procedure.

M' = parent_xform x local_xform x local_pivot

Memory management

Scene and Node does not create a copy of asset data(e.g. vertices, indices). Thus user must care about memory management of scene assets in user side.

API

API is still subject to change.

Node

void Node::SetName(const std::string &name);

Set (unique) name for the node.

void Node::AddChild(const type &child);

Add node as child node.

void Node::SetLocalXform(const T xform[4][4]) {

Set local transformation matrix. Default is identity matrix.

Scene

bool Scene::AddNode(const Node<T, M> &node);

Add a node to the scene.

bool Scene::Commit() {

Commit the scene. After adding nodes to the scene or changed transformation matrix, call this Commit before tracing rays. Commit triggers BVH build in each nodes and updates node's transformation matrix.

template<class H>
bool Scene::Traverse(nanort::Ray<T> &ray, H *isect, const bool cull_back_face = false) const;

Trace ray into the scene and find an intersection. Returns true when there is an intersection and hit information is stored in isect.

TODO

• Compute pivot point of each node(mesh).

Third party libraries and its icenses

• picojson : BSD license.
• bt3gui : zlib license.
• glew : BSD/MIT license.
• tinyobjloader : MIT license.
• glm : The Happy Bunny License (Modified MIT License). Copyright (c) 2005 - 2017 G-Truc Creation
• ImGui : The MIT License (MIT). Copyright (c) 2014-2015 Omar Cornut and ImGui contributors
• ImGuizmo : The MIT License (MIT). Copyright (c) 2016 Cedric Guillemet