Zink: Summer Update and SIGGRAPH 2019

Jul 25, 2019

Here’s an overview of the recent changes in Zink since the previous post, as well as an exciting announcement!

What’s new in the world of Zink?

OK, so I haven’t been as good at making frequent updates on as I was hoping, but let’s try to make up for it:

Since last time, there’s quite a lot of things that has been resolved:

We now do proper control-flow. This means things like if-statements, for-loops etc. There might be some control-flow primitives missing still, but that’s because I haven’t encountered any use yet.

Alpha testing has been implemented.

Client-defined clip-planes has been implemented.

Support for gl_FrontFacing has been implemented.

has been implemented. Lowering of glPointSize() to gl_PointSize has been implemented. This means you can use glPointSize() to specify sizes instead of having to write the gl_PointSize -output from the vertex shader.

to has been implemented. This means you can use to specify sizes instead of having to write the -output from the vertex shader. Support for gl_FragDepth has been implemented.

has been implemented. Two-sided lighting has been implemented.

Shadow-samplers has been implemented.

Support for 8-bit primitive indices has been implemented.

Occlusion queries has been implemented correctly across command buffers. This includes the ability to pause / restore queries.

The compiler has been ported to C.

The compiler no longer lowers IO, but instead process derefs directly.

The compiler now handles booleans properly. It’s no longer lowering them to floats.

David Airlie has contributed lowering of glShadeModel(GL_FLAT) to flat interpolation qualifiers. This still doesn’t give us the right result, because Vulkan only supports the first vertex as the provoking vertex, and OpenGL defaults to the last one. To resolve this in a reasonable way, we need to inject a geometry shader that reorders the vertices, but this hasn’t been implemented yet. You can read more about this in this ticket

to interpolation qualifiers. This still doesn’t give us the right result, because Vulkan only supports the first vertex as the provoking vertex, and OpenGL defaults to the last one. To resolve this in a reasonable way, we need to inject a geometry shader that reorders the vertices, but this hasn’t been implemented yet. You can read more about this in this ticket … and a boat-load of smaller fixes. There’s just too many to mention, really.

In addition to this, there’s been a pretty significant rewrite, changing the overall design of Zink. The reason for this, was that I made some early design-mistakes, and after having piled a bit too many features on top of this, I decided that it would be better to get the fundamentals right first.

Sadly, not all features have been brought forward since the rewrite, so we’re currently back to OpenGL 2.1 support. Fixing this is on my list of things I want to do, but I suspect that cleaning things up and upstreaming will take presedence over OpenGL 3.0 support.

And just to give you something neat to look at, here’s Blender running using Zink:

Blender on Zink

Khronos Vulkan BoF at SIGGRAPH 2019

Khronos has been nice enough to give me a slot in their Vulkan Sessions at the Khronos BoFs during SIGGRAPH 2019!

The talk will be a slightly less tech-heavy introduction to Zink, what it does and what the future holds. It will focus more on the motivation and use cases than the underlying technical difficulties compared to my previous talks.

So, if you’re in the area please drop by! A conference pass is not required to attend the BoF, as it’s not part of the official SIGGRAPH program.

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