Custom Mip Map Generation

Utility for generating custom mipmaps for power of two and non power of two textures by packing it into a texture and using custom sample functions. The pixel samples and weights are available to custom logic passed into the PackedMipmapGenerator constructor.

Demo Here

TODO

• Validate performance specifically when copying data to the back buffer on generation. It would be best to just copy instead of rerunning the mip map code again.
• Add a MipMapAtlasTarget class that inherits from WebGLRenderTarget it's easier to track what's been rendered to it and includes member getters for originalWidth, originalHeight, and mipLevels.
• Provide shader macro functions in mip map generation helper to avoid unneeded texture samples in case you want a sparser sample distribution like every other pixel.

Use

import { PackedMipmapGenerator } from './src/PackedMipmapGenerator.js';

// ...

const traditionalMipMapper = new PackedMipmapGenerator(
	`
	for ( int i = 0; i < SAMPLES; i ++ ) {

		gl_FragColor = samples[ i ] * weights[ i ];

	}
	`
);

mipMapper.update( texture, target, renderer );
mipMapper.dispose();

const maxMipMapper = new PackedMipmapGenerator(
	`
	for ( int i = 0; i < SAMPLES; i ++ ) {

		gl_FragColor = max( samples[ i ], gl_FragColor );

	}
	`
);

mipMapper.update( texture, target, renderer );
mipMapper.dispose();

API

PackedMipmapGenerator

constructor

constructor( logic : string )

Takes a block of code to generate the next mip level. Must set the gl_FragColor. An row major array of the parent sample values is available in the samples variable and weights in the weights variable. The number of samples, pixel width, and pixel height are available in SAMPLES, HEIGHT, and WIDTH defines.

.update

update( texture : Texture, target : WebGLRenderTarget, renderer : WebGLRenderer ) : Number

Takes a texture to turn into a mip pyramid, a target to to render the pyramid into, and a renderer to render with. Returns the number of mips generated.

.dispose

dispose() : void

Disposes of any created context objects.

Sample Functions

packedTexture2DLOD

// point sampled
vec4 packedTexture2DLOD( sampler2D texture, vec2 uv, int level )
vec4 packedTexture2DLOD( sampler2D texture, vec2 uv, int level, vec2 originalSize )

// interpolated
vec4 packedTexture2DLOD( sampler2D texture, vec2 uv, float level )
vec4 packedTexture2DLOD( sampler2D texture, vec2 uv, float level, vec2 originalSize )

// The sampler with the packed mipmaps
texture : sampler2D

// The uv in [ 0.0, 1.0 ] to sample
uv : vec2

// The mip level to sample
level : int | float

// The original size of the texture converted into the mipmap texture
// if the texture was generated with power to two enabled then this
// must be the power of to size. This is only useful for NPOT textures.
originalSize : vec2

Shader functions for sampling the generated texture at a specific mip level. If the int variant is used only a single texture sample is made.