Vulkan Grass Rendering

University of Pennsylvania, CIS 565: GPU Programming and Architecture, Project 6

• Yalun Hu
• Tested on: Windows 10, i7-6700HQ CPU @ 2.60GHz 32GB, GTX 1070 8192MB (Personal computer)

Features

1. Compute Shader

• Perform physics calculations on Bezier curves that represent individual grass blades.
  • Apply gravity, wind force, recovery force to each blade.
• Cull grass blades that don't contribute to a given frame.
  • Orientation culling
  • View-frustum culling
  • Distance culling

2. Graphics pipeline

• Vertex shader
  • transform Bezier control points from model space to world space.
• Tessellation control shader
  • Decide tesselation level.
• Tessellation evaluation shader
  • place the vertices in world space, respecting the width, height, and orientation information of each blade. Here I used triangle as the basic shape.
• Fragment shader
  • Lambert shading with a simple point light.

Performance Analysis

• Parameter:
  • Distance culling: Max depth = 50, Culling level = 10
  • View-frustum culling: tolerance = 1

It shows that culling really improves the performance, especially when the number of blades is big. For different three culling method, orientation culling has a bigger influence than other two methods, and view-frustum culling has less impact on the performance.

References

• Responsive Real-Time Grass Grass Rendering for General 3D Scenes
• CIS565 Vulkan samples
• Official Vulkan documentation
• Vulkan tutorial
• Tessellation tutorial