Type safe OpenGL – Converting strings into types in D | Hacker News Reader

Type safe OpenGL – Converting strings into types in D

maikklein.github.io

I'm currently doing something similar in C++ based on a project I worked on a couple of years ago. It is a wrapper around OpenGL for people like me who are tired of figuring out the specifics of the OpenGL calls every time they write something.

Goal: Easy access to shaders and its respective buffers with a bare bones visualization.

Example:

    Shader shader(fragment_shader, vertex_shader);
    verticesVBO.set(vertices);
    verticesVBO.map(shader, "inPosition", false);
    shader.bind();
    shader.setUniform("uViewMatrix", camera.view());
    shader.setUniform("uProjMatrix", camera.proj());
    shader.setUniform("uModelMatrix", modelMatrix());
    facesVBO.bind();
    glDrawElements(GL_TRIANGLES, facesVBO.length(), GL_UNSIGNED_INT, (void*) NULL);

I should clean it up and make it available as a library.

I've been fooling around with Go bindings to GL and also want to do something similar.

I still find it kind of uncomfortable that I'm copy-pasting variable names as strings between (the middle of!) the shader code string and the use sites (e.g. `setUniform` calls) -- I'd like it if I got some sort of quick compile time sanity check that those references match up. Had you considered going that far, and if so, what were your thoughts?

Not parent, but I wrote a shader introspector to reduce the pain of uniform mismatches as a (small) part of my master thesis.

My advice would be: don't do this.

If you can afford to support OpenGL 3.1+, use uniform buffer objects with the std140 layout instead. That way, you can create a strongly-typed struct in your code and access it normally on the CPU side. Uploading to the shader then is done with a single *BufferData call.

See [1] for more information.

[1] https://www.opengl.org/wiki/Uniform_Buffer_Object

glium in Rust does all of this and more (managing your state for you so you don't have to remember what is bound).

This only seems useful for user-defined glsl types. The builtin glsl types would only have to be written out once as D types.

The general idea of "importing" types is a good one and I think this is what F# achieves with type providers. I've seen this applied to database schemas and filesystems, but never OpenGL.

Maybe its because OpenTK has type safe bindings(OpenGL, OpenCL and OpenAL) for F# and C#.. http://www.opentk.com/

It took an awesome amount of work to get that level of type-safety. Now that this is in place, other languages could use that infrastructure to provide type-safe bindings:

https://github.com/opentk/opentk/tree/develop/Source/Bind/Sp...

The */override.xml files contain directives to convert the official Khronos XML specifications into type-safe versions. All you need is a code generator for your language of choice.

If anyone is interested in trying this, I encourage you to contact the developers on github (there used to be C++ and Java code generators that have since been removed.)

>there used to be C++ and Java code generators that have since been removed.

What was the reason for removal? Difficulty of maintenance? Out of scope for a C# project?

Mainly lack of an interested maintainer.

It's also a bit tricky because some .Net assumptions are hardcoded (i.e. overload resolution, generics, pointers+references), which makes it harder to generate idiomatic code for other languages. Nothing that cannot be fixed with a bit of effort if someone interested shows up, but until then it's better to generate excellent bindings for one runtime than mediocre bindings for multiple (and pretty much every runtime comes with a mediocre OpenGL binding.)

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