Silk.NET•3w ago

Hello I dont know why but I seem to be

Hello I dont know why but I seem to be unable to use gl.DrawElements and ebo I'm surelly missing something. Il make a thread to post my code and render doc result

27 Replies

Jemy191OP•3w ago

using Silk.NET.OpenGL;
using Silk.NET.Windowing;
using System.Drawing;

GL gl = null!;

var options = WindowOptions.Default;
options.Size = new Silk.NET.Maths.Vector2D<int>(800, 600);
options.Title = "Silk.NET OpenGL Triangle";

var window = Window.Create(options);

window.Load += OnLoad;
window.Render += OnRender;
window.Run();
return;

unsafe void OnLoad()
{
    gl = GL.GetApi(window);
    gl.ClearColor(Color.CornflowerBlue);

    Span<uint> indices = [0, 1, 2];
    Span<float> vertices =
    [
        0.0f, 0.5f, 0.0f,
        -0.5f, -0.5f, 0.0f,
        0.5f, -0.5f, 0.0f
    ];

    var vertexBuffer = gl.GenBuffer();
    gl.BindBuffer(BufferTargetARB.ArrayBuffer, vertexBuffer);

    fixed (void* d = vertices) { gl.BufferData(BufferTargetARB.ArrayBuffer, (nuint)(vertices.Length * sizeof(float)), d, BufferUsageARB.StaticDraw); }

    var indexBuffer = gl.GenBuffer();
    gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, indexBuffer);

    fixed (void* d = indices) { gl.BufferData(BufferTargetARB.ElementArrayBuffer, (nuint)(indices.Length * sizeof(uint)), d, BufferUsageARB.StaticDraw); }
    
    var vertexArray = gl.GenVertexArray();
    gl.BindVertexArray(vertexArray);
    gl.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), IntPtr.Zero);
    gl.EnableVertexAttribArray(0);
}

void OnRender(double delta)
{
    gl.Clear((uint)ClearBufferMask.ColorBufferBit);
    gl.DrawElements(PrimitiveType.Triangles, 3, DrawElementsType.UnsignedInt, UIntPtr.Zero);
}

using Silk.NET.OpenGL;
using Silk.NET.Windowing;
using System.Drawing;

GL gl = null!;

var options = WindowOptions.Default;
options.Size = new Silk.NET.Maths.Vector2D<int>(800, 600);
options.Title = "Silk.NET OpenGL Triangle";

var window = Window.Create(options);

window.Load += OnLoad;
window.Render += OnRender;
window.Run();
return;

unsafe void OnLoad()
{
    gl = GL.GetApi(window);
    gl.ClearColor(Color.CornflowerBlue);

    Span<uint> indices = [0, 1, 2];
    Span<float> vertices =
    [
        0.0f, 0.5f, 0.0f,
        -0.5f, -0.5f, 0.0f,
        0.5f, -0.5f, 0.0f
    ];

    var vertexBuffer = gl.GenBuffer();
    gl.BindBuffer(BufferTargetARB.ArrayBuffer, vertexBuffer);

    fixed (void* d = vertices) { gl.BufferData(BufferTargetARB.ArrayBuffer, (nuint)(vertices.Length * sizeof(float)), d, BufferUsageARB.StaticDraw); }

    var indexBuffer = gl.GenBuffer();
    gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, indexBuffer);

    fixed (void* d = indices) { gl.BufferData(BufferTargetARB.ElementArrayBuffer, (nuint)(indices.Length * sizeof(uint)), d, BufferUsageARB.StaticDraw); }
    
    var vertexArray = gl.GenVertexArray();
    gl.BindVertexArray(vertexArray);
    gl.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), IntPtr.Zero);
    gl.EnableVertexAttribArray(0);
}

void OnRender(double delta)
{
    gl.Clear((uint)ClearBufferMask.ColorBufferBit);
    gl.DrawElements(PrimitiveType.Triangles, 3, DrawElementsType.UnsignedInt, UIntPtr.Zero);
}

Also when I use (void*)0 instead of UIntPtr.Zero in DrawElement it throw this: System.ExecutionEngineException

Jemy191OP•3w ago

When using DrawArray

Jemy191OP•3w ago

When using DrawElement

Jemy191OP•3w ago

Really weird that it won't work. I must be missing some little simple thing.

Aqua•3w ago

You are creating your vertex array after you create the buffers. This means that your BindBuffer calls are not being bound to the vertex array and are instead being bound to the “null” vertex array. Create and bind your vertex array before you create the buffers and see how it goes I’m slightly surprised that DrawArray works at all either

Jemy191OP•3w ago

Me too that was thowing me off XD

Aqua•3w ago

You should also be using (void*) 0 instead of uintptr, as I believe silk will try and interpret that as a value and it won’t work I may be misremembering but I believe that is the case

Jemy191OP•3w ago

Yeah if I use (void*) 0 with DrawElement it throw but with UIntPtr.Zero it just do not draw🙃

Aqua•3w ago

Yeah, the throwing behaviour is normal when somethings incorrect Seems better than it used to be tho, when I was first implementing silk on Linux it crashed my entire driver several times lol

Jemy191OP•3w ago

So you said: Gen and bind the vertexArray, Gend, bind and send vertBuffer and gen, bind and send indexBuffer. Right? it wont work using the (void*) 0 too

Aqua•3w ago

Another issue I can see is that you are enabling the vertex attrib array after setting its pointer, I don’t know for sure but I’ve never seen it done in that order so I wouldn’t be surprised if it’s not working

Jemy191OP•3w ago

So gen bind enable and Set pointer? It wont work either

Aqua•3w ago

Is this your entire code?

Jemy191OP•3w ago

yes

Aqua•3w ago

Ah. You haven’t created a shader of any kind, you’ll need that to draw anything

Jemy191OP•3w ago

But if I use DrawArrays it work and I have a black triangle🙃 Il add a shader to see if it help in any way

Aqua•3w ago

Yeah that’s very… odd… behaviour, definitely not spec compliant that’s for sure

Aqua•3w ago

I can recommend you follow the silk tutorials if you aren’t already, they go through everything in detail! https://dotnet.github.io/Silk.NET/docs/opengl/c1/2-hello-quad.html

Silk.NET - High-Speed & Advanced .NET Graphics & Compute

1.2 - Hello Quad

Jemy191OP•3w ago

Omg yes I follow it a while ago. I want thinking there was no use of Ebo. I'll do that real quick

Aqua•3w ago

Don’t worry there’s full use of everything to draw a quad including element buffers and shaders!

Jemy191OP•3w ago

Thanks for pointing me the obvious 😅 The tutorial code work. I started my project so long ago that I was thinking I did the basic stuff right🙃

Aqua•3w ago

Haha no worries it happens

Jemy191OP•3w ago

Sometime it so simple and obvious that you don't think of it 🤣

Aqua•3w ago

Don’t worry about it, graphics programming is just like that sometimes lol

Jemy191OP•3w ago

Yeah it pretty hard sometime XD. It kinda work in my engine now 🙂 My abstraction was making thing out of order😅 Little question should I not be able to create the vbo and vbo prior to creating the vao and just rebinding the vbo and vbo after the vao? Ex:

        handle = this.gl.GenVertexArray();
        Bind();
        vbo.Bind();
        ebo.Bind();

        handle = this.gl.GenVertexArray();
        Bind();
        vbo.Bind();
        ebo.Bind();

Aqua•3w ago

Yep you can do that as well. As long as you bind them after the vertex array has been created, it doesn’t matter when you create the buffers. Just be aware that if you create buffers before binding them to a VAO, you should always call BindVertexArray(0) before creating them as otherwise you risk overwriting a previously bound vertex array.

Jemy191OP•2w ago

Thanks

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Hello I dont know why but I seem to be

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