Utils

The wgpu library provides a few utilities. Note that the functions below need to be explictly imported.

Get default device

wgpu.utils.get_default_device()

Get a wgpu device object. If this succeeds, it’s likely that the WGPU lib is usable on this system. If not, this call will probably exit (Rust panic). When called multiple times, returns the same global device object (useful for e.g. unit tests).

Compute with buffers

wgpu.utils.compute_with_buffers(input_arrays, output_arrays, shader, n=None)

Apply the given compute shader to the given input_arrays and return output arrays. Both input and output arrays are represented on the GPU using storage buffer objects.

Parameters:

  • input_arrays (dict) – A dict mapping int bindings to arrays. The array can be anything that supports the buffer protocol, including bytes, memoryviews, ctypes arrays and numpy arrays. The type and shape of the array does not need to match the type with which the shader will interpret the buffer data (though it probably makes your code easier to follow).

  • output_arrays (dict) – A dict mapping int bindings to output shapes. If the value is int, it represents the size (in bytes) of the buffer. If the value is a tuple, its last element specifies the format (see below), and the preceding elements specify the shape. These are used to cast() the memoryview object before it is returned. If the value is a ctypes array type, the result will be cast to that instead of a memoryview. Note that any buffer that is NOT in the output arrays dict will be considered readonly in the shader.

  • shader (str or bytes) – The shader as a string of WGSL code or SpirV bytes.

  • n (int, tuple, optional) – The dispatch counts. Can be an int or a 3-tuple of ints to specify (x, y, z). If not given or None, the length of the first output array type is used.

Returns:

A dict mapping int bindings to memoryviews.

Return type:

output (dict)

The format characters to cast a memoryview are hard to remember, so here’s a refresher:

  • “b” and “B” are signed and unsiged 8-bit ints.

  • “h” and “H” are signed and unsiged 16-bit ints.

  • “i” and “I” are signed and unsiged 32-bit ints.

  • “e” and “f” are 16-bit and 32-bit floats.

Shadertoy

from wgpu.utils.shadertoy import Shadertoy
class wgpu.utils.shadertoy.Shadertoy(shader_code, resolution=(800, 450))

Provides a “screen pixel shader programming interface” similar to shadertoy.

It helps you research and quickly build or test shaders using WGSL or GLSL via WGPU.

Parameters:

  • shader_code (str) – The shader code to use.

  • resolution (tuple) – The resolution of the shadertoy.

The shader code must contain a entry point function:

WGSL: fn shader_main(frag_coord: vec2<f32>) -> vec4<f32>{} GLSL: void shader_main(out vec4 frag_color, in vec2 frag_coord){}

It has a parameter frag_coord which is the current pixel coordinate (in range 0..resolution, origin is bottom-left), and it must return a vec4<f32> color (for GLSL, it’s the out vec4 frag_color parameter), which is the color of the pixel at that coordinate.

some built-in variables are available in the shader:

  • i_time: the global time in seconds

  • i_time_delta: the time since last frame in seconds

  • i_frame: the frame number

  • i_resolution: the resolution of the shadertoy

  • i_mouse: the mouse position in pixels

For GLSL, you can also use the aliases iTime, iTimeDelta, iFrame, iResolution, and iMouse of these built-in variables, the entry point function also has an alias mainImage, so you can use the shader code copied from shadertoy website without making any changes.

property resolution

The resolution of the shadertoy as a tuple (width, height) in pixels.

property shader_code

The shader code to use.

property shader_type

The shader type, automatically detected from the shader code, can be “wgsl” or “glsl”.