mistodon
commented
3 years ago Hi!
So these tutorials purposely don't support OpenGL. This is partly because when I started them, the setup for OpenGL was drastically different and it would've complicated the tutorials. But it's also because OpenGL is just less compatible with the gfx/Vulkan API in general. There's a lot of finnicky little differences and (probably) bugs. That's not to say I'll never support OpenGL - I've actually been looking into it for another project - but for now, I can't guarantee that anything in this repo will work with it.
That said, I'll keep this open to at least track the issue. And I can try to help a little.
One thing I ran into when trying to get OpenGL working is that push constants are just not really something it supports. Gfx-hal I believe tries to simulate them with a single shader uniform, but I've not managed to get a push constants struct working in OpenGL. This might be the problem you're seeing. To test this, you could maybe try packing all the data into one field. I'm running on macOS but this seemed to work for me, with the OpenGL backend:
// part-2.vert
#version 450
#extension GL_ARB_separate_shader_objects : enable
layout(push_constant) uniform PushConstants {
vec4 pos_scale;
} push_constants;
layout(location = 0) out vec4 vertex_color;
vec2 positions[3] = vec2[](
vec2(0.0, -0.5),
vec2(-0.5, 0.5),
vec2(0.5, 0.5)
);
void main() {
vec2 pos = positions[gl_VertexIndex] * push_constants.pos_scale.zw;
vertex_color = vec4(1.0, 1.0, 1.0, 1.0);
gl_Position = vec4((pos + push_constants.pos_scale.xy), 0.0, 1.0);
}// part-2-push-constants.rs
...
#[repr(C)]
#[derive(Debug, Clone, Copy)]
struct PushConstants {
pos_scale: [f32; 4],
}
...
let triangles = &[
// Red triangle
PushConstants {
pos_scale: [-0.5, -0.5, small[0], small[1]],
},
...
};
...Obviously this is pretty restrictive - hardcoding color etc. You could pack even more information into one field if you use a mat4, but probably it would be a better idea to avoid push constants entirely for OpenGL and use descriptor sets instead. Part 4 will talk about those, but no promises on when I finish that š¬.
Still, I hope this explains some things - and maybe unblocks you from playing around with gfx-hal a bit more!
helmet91
Hello,
I have encountered the following issue in part-2 of the tutorial: A black window appears when I'm trying to run the program. There are no errors on the console, neither during compilation, nor during runtime.
Environment: Linux OS with X11
Hardware:
As I have no access to a Vulkan-capable hardware, I switched to the
glbackend. Also, I have added the x11 feature to the Cargo.toml file as follows:With both rendering devices mentioned above, I get a black window, no triangles are shown. The part-1 of the tutorial worked correctly.
I have also tried to upgrade all dependencies in Cargo.toml to the currently available most up-to-date versions. This didn't fix the issue, while part-1 of the tutorial still worked.
Note: after upgrading winit,
let dpi = event_loop.primary_monitor().scale_factor();has to be changed to something likelet dpi = event_loop.primary_monitor().unwrap().scale_factor();, as theevent_loop.primary_monitor()method now returns anOption.Now, as I get no errors at all, I have absolutely no clue where to even start with debugging the code.