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Improve ShaderCreateStep to work around cache issues

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This commit is contained in:
Robin Voetter
2022-12-29 23:53:09 +01:00
parent d9377c4c70
commit f7a4e4346e
4 changed files with 179 additions and 166 deletions
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README.md
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@@ -242,7 +242,7 @@ pub const xcb_connection_t = if (@hasDecl(root, "xcb_connection_t")) root.xcb_co
For some times (such as those from Google Games Platform) no default is known. Usage of these without providing a concrete type in the project root generates a compile error.
### Shader compilation
vulkan-zig provides functionality to help compiling shaders using glslc. It can be used from build.zig as follows:
vulkan-zig provides functionality to help compiling shaders to spir-v using glslc. It can be used from build.zig as follows:
```zig
const vkgen = @import("vulkan-zig/generator/index.zig");
@@ -254,15 +254,20 @@ pub fn build(b: *Builder) void {
const gen = vkgen.VkGenerateStep(b, "path/to/vk.xml", "vk.zig");
exe.addPackage(gen.package);
const shader_comp = vkgen.ShaderCompileStep.init(
const shader_comp = vkgen.ShaderCompileStep.create(
builder,
&[_][]const u8{"glslc", "--target-env=vulkan1.2"}, // Path to glslc and additional parameters
);
exe.step.dependOn(&shader_comp.step);
const spv_path = shader_comp.addShader("path/to/shader.frag");
exe.addPackage(shader_comp.getPackage("shaders"));
shader_comp.add("shader", "path/to/shader.frag", .{});
}
```
Upon compilation, glslc is then invoked to compile each shader, and the result is placed within `zig-cache`. `addShader` returns the full path to the compiled shader code. This file can then be included in the project, as is done in [build.zig for the example](build.zig) by generating an additional file which uses `@embedFile`.
Upon compilation, glslc is then invoked to compile each shader, and the result is placed within `zig-cache`. All shaders which are compiled using a particular `ShaderCompileStep` are imported in a single Zig file using `@embedFile`, and this file can be added to an executable as a package using `getPackage`. To slightly improve compile times, shader compilation is cached; as long as a shader's source and its compile commands stay the same, the shader is not recompiled. The spir-v code for any particular shader is aligned to that of a 32-bit integer as follows, as required by vkCreateShaderModule:
```zig
pub const ${name} align(@alignOf(u32)) = @embedFile("${path}").*;
```
See [build.zig](build.zig) for a working example.
## Limitations
* Currently, the self-hosted version of Zig's cache-hash API is not yet ready for usage, which means that the bindings are regenerated every time an executable is built.