Sampler

A Sampler is an immutable object that holds a set of sampling parameters for texture access. Sampling parameters are applied during shader execution and control how values ("texels") are read from textures.

Note that luma.gl automatically creates a default Sampler for each Texture. A texture's default sampler parameters can be specified creating the texture via device.createTexture({sampler: SamplerProps})). Unless an application needs to render the same texture with different sampling parameters, an application typically does not need to explicitly instantiate samplers.

Note that a Comparison sampler is a special type of Sampler that compares against the depth buffer. During comparison sampling, the interpolated and clamped r texture coordinate is compared to currently bound depth texture, and the result of the comparison (0 or 1) is assigned to the red channel. Specifying the type: 'comparison-sampler' sampler property creates a comparison sampler.

Usage

Create a new Sampler

import {luma} from '@luma.gl/core';
const device = await luma.createDevice();
const sampler = device.createSampler(gl, {
  addressModeU: 'clamp-to-edge'
});

Note that a default Sampler is automatically created for each texture:

// Create a texture
const texture = device.createTexture({
  sampler: {
    minFilter: 'linear',
    maxFilter: 'linear'
  }
});
console.log(texture.sampler);

Create a new comparison sampler, by specifying the compare sampler property creates a comparison sampler.

const sampler = device.createSampler(gl, {
  compare: 'lequal'
});

Types

SamplerProps

Sampler Parameter	Values	Description
type	'color-sampler' * | 'comparison-sampler'	Specify 'comparison-sampler' to create a depth comparison sampler
addressModeU?	'clamp-to-edge' * | 'repeat' | 'mirror-repeat'	Texture wrapping for texture coordinate u (s)
addressModeV?	'clamp-to-edge' * | 'repeat' | 'mirror-repeat'	Texture wrapping for texture coordinate v (t)
addressModeW?	'clamp-to-edge' * | 'repeat' | 'mirror-repeat'	Texture wrapping for texture coordinate w (r)
magFilter?	'nearest' * | 'linear'	Sample nearest texel, or interpolate closest texels
minFilter?	'nearest' * | 'linear'	Sample nearest texel, or interpolate closest texels
mipmapFilter?	'nearest' * | 'linear'	Sample closest mipmap, or interpolate two closest mipmaps
maxAnisotropy?	number	Combine samples from multiple mipmap levels when appropriate
lodMinClamp?	number	Minimum level of detail to use when sampling
lodMaxClamp?	number	Maximum level of detail to use when sampling
compare?	less-equal etc (see below)	Specifies compare function for a depth "comparison sampler"

Texture Wrapping

Controls how texture coordinates outside of the [0, 1] range are sampled.

• Parameters: addressModeU, addressModeV, addressModeW

Value	Description
repeat (default)	use fractional part of texture coordinates
clamp-to-edge	clamp texture coordinates
mirrored-repeat	use fractional part of texture coordinate if integer part is odd, otherwise 1 - frac

Texture Magnification Filter

Controls how a pixel is textured when it maps to less than one texel.

Parameter: magFilter

Value	Description
nearest (default)	nearest texel
linear	interpolated texel

• nearest is faster than linear, but is not as smooth.

Texture Minification Filter

Controls how a pixel is textured when it maps to more than one texel.

Parameter: minFilter

Value	Description
nearest (default)	nearest texel
linear	interpolated texel

Texture Mipmap Filter

Controls if a pixel is textured by referencing more than one mipmap level.

Parameter: mipmapFilter

Value	Description
nearest (default)	nearest mipmap
linear	interpolate between mipmaps
N/A	no mipmaps

Texture Max Anisotropy

Controls multiple mipmap level can be consulted when texturing a pixel.

Texture Comparison Function

Specifying the compare sampler property creates a comparison sampler. Comparison samplers are special samplers that compare a value against the depth buffer.

Parameter: compare

`Value	Computed result
less-equal (default)	result = 1.0 0.0, r <= D t r > D t
greater-equal	result = 1.0 0.0, r >= D t r < D t
less	result = 1.0 0.0, r < D t r >= D t
greater	result = 1.0 0.0, r > D t r <= D t
equal	result = 1.0 0.0, r = D t r ≠ D t
not-equal	result = 1.0 0.0, r ≠ D t r = D t
always	result = 1.0
never	result = 0.0

During sampling, the interpolated and clamped r texture coordinate is compared to currently bound depth texture, and the result of the comparison (0 or 1) is assigned to the red channel.

Members

• device: Device - holds a reference to the Device that created this Sampler.
• handle: unknown - holds the underlying WebGL or WebGPU shader object
• props: SamplerProps - holds a copy of the SamplerProps used to create this Sampler.

Methods

constructor(props: SamplerProps)

Sampler is an abstract class and cannot be instantiated directly. Create with device.createSampler(...).

device.createSampler({...})

destroy(): void

Free up any GPU resources associated with this sampler immediately (instead of waiting for garbage collection).

Remarks

• WebGL: More information about WebGLSampler can be found in the OpenGL Wiki.