Dispose tile textures

[StrandedKitty]

I've read through the code and haven't found any mention of deleting old tile textures. In Three.js textures need to be deleted explicitly, see Textures section here: https://threejs.org/docs/#manual/en/introduction/How-to-dispose-of-objects

In this PR I've added Texture.dispose() for color textures and heightmap textures (only for MapHeightNodeShader). I'm not sure whether this is the best way to implement this.

[aldipower]

Ha, what an coincidence.
Having troubles which faster moving maps, where memory is eaten more and more up by geo-three to the point the browser crashes.

I started to look into the geo-three myself and came to something similar with disposing objects and tiles, but unfortunately I was unable to compile geo-three only getting this error at runtime, so I could not proceed.:

THREE.WebGLProgram: Shader Error 0 - VALIDATE_STATUS false

Program Info Log: Must have a compiled vertex shader attached:

Here is a memory snapshot during runtime, all this objects and arrays building more and more up, and never gets released, until the point of crash.

I think this are not only map textures, but also meshes and other three.js objects, that never gets disposed.

@tentone Would be great, if you find some time to help us with this issue and maybe we can get to new release together with fixes tackling cleanup issues.

[StrandedKitty]

@aldipower Just to clarify, are you talking about RAM or VRAM? In this PR I'm addressing a possible VRAM leak (textures from disposed tiles don't get removed from VRAM). But you've shown a heap snapshot, so I don't really understand what's this about. If you have a heap snapshot it shouldn't be hard for you to find the source of your memory leak.

[aldipower]

@StrandedKitty Yes, my post does not address directly, but maybe partly, your PR I guess.
My post is about geo-three is filling up the RAM, when used in long or fast running scences.
The relation to your PR is 'cleaning up unused objects generally'.

My problem is, if I compile geo-three myself, I cannot run the lib, because I get this THREE.WebGLProgram: Shader Error 0 - VALIDATE_STATUS false error, which I do not get at the pre-compiled lib. So, I cannot test any code changes, I potentially can do. How did you develop on geo-three?

[tentone]

Thanks a lot!

Completly missed these. PR merged! Build seems to be failing but should be an easy fix!