OBJ Support for Manim

[MrDiver]

• OBJMobject for rendering .obj files [WIP] #2030

Overview: What does this pull request change?

Add an OBJMobject which allows users to make use of 3D models from .obj files.

Motivation and Explanation: Why and how do your changes improve the library?

It's tedious and laborious to make complex 3D models in Manim by hand. One can now make a 3D model in 3rd party software better suited to the task (such as Blender) and import the model into Manim using OBJMobject.

One can use OBJMobject like so:

class Test(ThreeDScene):
    def construct(self):
        self.set_camera_orientation(
            phi=-45 * DEGREES,
            theta=-135 * DEGREES,
            gamma=-55 * DEGREES)
        model = OBJVMobject("/Users/aathishs/Projects/Python/ManimStuff/manim-projects/threedfilemob/airboat.obj").scale(0.5)
        self.play(Write(model))
        self.play(Rotate(model,axis=UP,angle=2*PI),run_time=5,rate_func=linear)
        self.wait(1)

The Output for the code above is:
Test.mp4

Links to added or changed documentation pages

Documentation is WIP

Further Information and Comments

The .obj file can be found at :

https://people.sc.fsu.edu/~jburkardt/data/obj/airboat.obj

And the .mtl file for textures is available at:

https://people.sc.fsu.edu/~jburkardt/data/obj/vp.mtl

NOTES: The colour bronze has to be changed to brass in the .obj file for colours to render properly. The vp.mtl file must be renamed to airboat.mtl and be placed next to the airboat.obj file for colours to render properly.

This is very much a work in progress. OpenGL support is untested, and much of the OBJ file spec is not yet implemented. The OBJ file specifications can be found here: http://paulbourke.net/dataformats/obj/ In the near future, I'll add a checklist of stuff that's yet to be implemented from the .obj and .mtl file spec.

Reviewer Checklist

* [ ]  The PR title is descriptive enough for the changelog, and the PR is labeled correctly

* [ ]  If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section

* [ ]  If applicable: newly added functions and classes are tested