Vulkan Graphics pipeline basics

Input Assembler fixed-function stages

• Collects raw vertex data from specified buffers
• Optionally uses an index buffer to reuse elements without duplication

Vertex Shader programmable stages

• Executed for every vertex
• Performs:
  • Model space → Screen space transformations
  • Passes per-vertex data downstream

Tessellation Shaders (Optional) programmable stages

• Subdivides geometry based on rules
• Common uses:
  • Enhancing surface detail (e.g. brick walls, stairs)
  • Dynamic LOD adjustments

Geometry Shader (Optional) programmable stages

• Processes each primitive (triangle/line/point)
• Capabilities:
  • Discard primitives
  • Emit additional primitives
• Performance note:
  • Generally inefficient on discrete GPUs
  • Better supported on Intel integrated graphics

Rasterization fixed-function stages

• Discretizes primitives into fragments (potential pixels)
• Key operations:
  • Viewport culling (discards off-screen fragments)
  • Attribute interpolation (across fragments)
  • Early depth/stencil testing

Fragment Shader programmable stages

• Executed for every surviving fragment
• Determines:
  • Framebuffer write targets
  • Final color/depth values
• Uses interpolated vertex data:
  • Texture coordinates
  • Normals (for lighting)

Color Blending fixed-function stages

• Combines fragments mapping to same framebuffer pixel
• Blend modes:
  • Overwrite
  • Additive
  • Alpha blending
  • Custom programmable blending

Attention: 在Vulkan中，图形管线几乎完全不可变，所以如果你想更改着色器、绑定不同的帧缓冲区或改变混合函数，就必须从头重新创建管线。这样做的缺点是，你必须创建多个管线，来代表你在渲染操作中想要使用的所有不同状态组合。然而，由于在管线中要进行的所有操作都是预先可知的，驱动程序能够对其进行更优的优化。