NVIDIA recently released an open source sample of a GLSL header generator for DescriptorSet-indexed types in Vulkan. The project demonstrates how to simplify usage of VK_EXT_descriptor_indexing and GL_EXT_nonuniform_qualifier within GLSL. A script generates structure and function overloads to hide the code for indexing descriptor sets of samplers and textures.

For example, the tool turns:

// BEFORE

// we use a big resource table for descriptorset indexing
layout(set = 0, binding=0) uniform sampler2D  res_tex2Ds[];

// let's make use of GL_EXT_buffer_reference2
layout(buffer_reference, scalar) buffer Material {
  // we want to be cache efficient 
  uint16_t albedoTex;
  uint16_t normalTex;
  ...
};

layout(push_constant, scalar) uniform inputData {
  Material materials;
};

  // example usage
  Material  mat = materials[idx];
  
  // if idx varies non-uniformly (e.g. raytracing)
  // our texture fetches can start to look pretty ugly
  
  vec4 albedo = texture(res_tex2Ds[nonuniformEXT(uint(mat.albedoTex))], uv);

into:

// AFTER

// where descriptorsets start that are used for indexing
#define DIT_DSET_IDX 0

// this file is generated by the lua script
#include "sampler_indexed_types.glsl"

layout(buffer_reference, scalar) buffer Material {
  // new types are available
  // for example: struct sampler2D_u16 { uint16_t idx; }
  
  sampler2D_u16 albedoTex;
  sampler2D_u16 normalTex;
  ...
};

layout(push_constant, scalar) uniform inputData {
  Material materials;
};

  // example usage
  Material  mat = materials[idx];
  
  // much nicer looking access
  vec4 albedo = texture(mat.albedoTex, uv);

Check out the blog post for more information and the Github project here.

View full story