# orx-obj-loader

Simple loader and saver for Wavefront .obj 3D mesh files.

##### Usage

Loading directly into a vertex buffer can be done through `loadOBJasVertexBuffer`.

```kotlin
val vertexBuffer = loadOBJasVertexBuffer("data/someObject.obj")
```

The loaded vertex buffer can be drawn like this:

```kotlin
drawer.vertexBuffer(vertexBuffer, DrawPrimitive.TRIANGLES)
```

To save a vertex buffer as an .obj file:

```kotlin
vertexBuffer.saveOBJ("my/path/exported.obj")
```

<!-- __demos__ -->
## Demos
### DemoObjCompoundRW01

This program loads an OBJ mesh as a CompoundMeshData and demonstrates
how to convert it to a OBJ String representation, then
draws the beginning of this String on the program window.

![DemoObjCompoundRW01Kt](https://raw.githubusercontent.com/openrndr/orx/media/orx-obj-loader/images/DemoObjCompoundRW01Kt.png)

[source code](src/jvmDemo/kotlin/DemoObjCompoundRW01.kt)

### DemoObjLoader01

Demonstrates how to load a `.obj` file as a `VertexBuffer`.

The `loadOBJasVertexBuffer()` function expects the path to the `.obj` file as an argument.


![DemoObjLoader01Kt](https://raw.githubusercontent.com/openrndr/orx/media/orx-obj-loader/images/DemoObjLoader01Kt.png)

[source code](src/jvmDemo/kotlin/DemoObjLoader01.kt)

### DemoObjSaver01

Demonstrates how to save a `VertexBuffer` as an `.obj` file using the
`VertexBuffer.saveOBJ()` method.

The program loads an existing OBJ file, then saves it with a new file name.

![DemoObjSaver01Kt](https://raw.githubusercontent.com/openrndr/orx/media/orx-obj-loader/images/DemoObjSaver01Kt.png)

[source code](src/jvmDemo/kotlin/DemoObjSaver01.kt)

### DemoObjSaver02

Demonstrates saving a `VertexBuffer` generated via code as an OBJ file.

This file can be loaded in a 3D modelling / rendering program.


![DemoObjSaver02Kt](https://raw.githubusercontent.com/openrndr/orx/media/orx-obj-loader/images/DemoObjSaver02Kt.png)

[source code](src/jvmDemo/kotlin/DemoObjSaver02.kt)

### DemoWireframe01

Demonstrates two approaches for loading an OBJ file: as a `VertexBuffer` and as `CompoundMeshData`.

A `CompoundMeshData` object contains vertices, texture coordinates, colors, normals, tangents, and bitangents,
alongside their associated face indices, grouped into meshes.

In this demo `CompoundMeshData.wireframe()` is called to generate a wireframe representation of the loaded mesh.

When rendering the wireframe, a shade style is used to displace the lines slightly towards the camera, to ensure
the lines do not end up occluded by the mesh rendered as triangles.

Finally, the `sub` method is called on the `Path3D` instances to draw only parts of the wireframe, creating
an animated effect.

![DemoWireframe01Kt](https://raw.githubusercontent.com/openrndr/orx/media/orx-obj-loader/images/DemoWireframe01Kt.png)

[source code](src/jvmDemo/kotlin/DemoWireframe01.kt)