I'm new to graphics and game design and I just wanted to know if a compute pipeline could be as efficient as a render pipeline for rasterization and an explanation on how and why. Also is it possible to manually perform rasterization with a render pipeline as in manipulate individual pixel data in a metal texture yourself but do it with a render pipeline?
Can a compute pipeline be as efficient as a render pipeline for rasterization?
The render pipeline has dedicated fixed-function hardware for rasterization — vertex assembly, primitive rasterization, depth/stencil testing, and blending all happen in hardware that's purpose-built for this work. A compute pipeline can't match this for rasterization because you'd be reimplementing all of that in software on the CPU.
Fragment shaders in a render pipeline do operate on individual pixel data — that's their purpose. The rasterizer determines which pixels a triangle covers, then the fragment shader runs for each of those pixels, giving you full control over the output color.
These resources are a good starting point for understanding both pipelines:
- Using Metal to Draw a View's Contents — basic MetalKit setup and rendering
- Performing Calculations on a GPU — shows the compute pipeline
- Metal Sample Code — the full collection of Metal samples, starting with the fundamentals section
Working through the render pipeline samples first will give you a practical understanding of how rasterization works on the GPU.