https://github.com/nvpro-samples/vk_raytrace_displacement

https://github.com/nvpro-samples/vk_raytrace_displacement

Last synced: about 1 year ago
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• Host: GitHub
• URL: https://github.com/nvpro-samples/vk_raytrace_displacement
• Owner: nvpro-samples
• License: apache-2.0
• Created: 2023-12-06T21:50:53.000Z (over 2 years ago)
• Default Branch: main
• Last Pushed: 2024-10-28T10:32:17.000Z (over 1 year ago)
• Last Synced: 2024-10-28T13:52:09.828Z (over 1 year ago)
• Language: C++
• Size: 154 KB
• Stars: 3
• Watchers: 9
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Contributing: CONTRIBUTING.txt
  • License: LICENSE

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README

          
# DEPRECATED

The **NVIDIA RTX Mega Geometry** technology supercedes displaced Micro-Meshes. This repository is archived as result.

Please have a look at this new sample [vk_tessellated_clusters](https://github.com/nvpro-samples/vk_tessellated_clusters) that showcases real-time adaptive tessellation with displacement for ray tracing and rasterization.

# vk_raytrace_displacement

![](doc/preview.jpg)

This sample demonstrates the use of the

[`heightmap_rtx`](https://github.com/NVIDIAGameWorks/heightmap_rtx) library to

raytrace dynamically displaced geometry. `heightmap_rtx` is a small Vulkan

library to displace raytraced triangles with a heightmap. It uses [NVIDIA

Micro-Mesh](https://developer.nvidia.com/rtx/ray-tracing/micro-mesh)

([Toolkit](https://github.com/NVIDIAGameWorks/Displacement-MicroMap-Toolkit))

internally.

A notable feature of this sample is animation. A single and static

`VkCommandBuffer` that `heightmap_rtx` populates is resubmitted each frame

before building the acceleration structure. This allows convenient animation

without any mid-frame resource allocation for building the Micro-Map.

## Requirements

[`heightmap_rtx`](https://github.com/NVIDIAGameWorks/heightmap_rtx) is a

submodule. Run `git submodule update --init --recursive`.

Along with other nvpro samples, `nvpro_core` and the `VulkanSDK` are required to

build this project. Cmake will look in the parent directory for nvpro_core and

the VulkanSDK is typically found via environment variables.

[VK_NV_displacement_micromap](https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VK_NV_displacement_micromap.html)

is required. See [device

support](https://vulkan.gpuinfo.org/listdevicescoverage.php?extension=VK_NV_displacement_micromap&platform=all).

> [!IMPORTANT]

> `VK_NV_displacement_micromap` likely requires recent NVIDIA [vulkan beta

> drivers](https://developer.nvidia.com/vulkan-driver) (>= 537.96) and

> [VulkanSDK](https://vulkan.lunarg.com/) (>= 1.3.268.0), particularly for GLSL

> `NV_displacement_micromap` support.

## Motivation

To render displacement with rasterization, one might use a tessellation shader,

mesh shader or trace the heightmap in a frament shader with parallax mapping. In

constrast, the vulkan raytracing API would normally only take regular triangle

geometry. A base mesh would need to be tessellated and displaced before building

the acceleration structure. This limitation is noted by [^1], in which heightmap

displacement traced directly using min-max mipmap acceleration similarly to [^2]

and [^3]. An alternative to tessellating geometry is NVIDIA Micro-Mesh. This GPU

feature offers a way to apply displacement without tessellating in the

application code. The vulkan raytracing acceleration structure build step is

also faster when using Micro-Mesh. However, building the Micro-Map that holds

the displacement is not trivial to code. The `heightmap_rtx` library simplifies

that step, taking just a `VkImage` displacement image and converting it before

the acceleration structure build.

## Limitations

There are a number of limitations of `heightmap_rtx` when used for displacement.

Please see the README in its repository for details. A significant one with

regard to correctness is that direction vectors are not normalized after

interpolation. This means displacement near high base mesh curvature will

produce quite different results.

[^1]: Theo Thonat, Francois Beaune, Xin Sun, Nathan Carr, and Tamy Boubekeur.

    2021. Tessellation-free displacement mapping for ray tracing. ACM Trans.

    Graph. 40, 6, Article 282 (December 2021)


[^2]: Kyoungsu Oh, Hyunwoo Ki, and Cheol-Hi Lee. 2006. Pyramidal displacement

    mapping: a GPU based artifacts-free ray tracing through an image pyramid. In

    Proceedings of the ACM symposium on Virtual reality software and technology

    (VRST '06)


[^3]: Art Tevs, Ivo Ihrke, and Hans-Peter Seidel. 2008. Maximum mipmaps for

    fast, accurate, and scalable dynamic height field rendering. In Proceedings

    of the 2008 symposium on Interactive 3D graphics and games (I3D '08)