Memory usage with glBufferData

OpenGL OpenGL: Basic Coding
1

Hello everyone,

I am trying to create a simple CAD application using OpenTK (C#).
However I’m running into a problem, when I call GL.BufferData(…) it uses much more memory than it should need.

for instance if I draw 4000 lines the process memory shoots up 300+ mb. but it should only be a couple of kb.

I have a simple mesh class:

public abstract class Mesh
{
    private int VertexArrayObject { get; set; }
    private int VertexBufferObject { get; set; }
    private int ElementBufferObject { get; set; }
    private int NumberOfVertices { get; set; }
    public abstract PrimitiveType PrimitiveType { get; }

    public void Update(float[] vertices, uint[] indices)
    {
        NumberOfVertices = indices.Length;
        GL.BindVertexArray(VertexArrayObject);
        GL.BindBuffer(BufferTarget.ArrayBuffer, VertexBufferObject);
        GL.BufferData(BufferTarget.ArrayBuffer, vertices.Length * sizeof(float), vertices, 
                   BufferUsageHint.DynamicDraw);
        GL.BindBuffer(BufferTarget.ElementArrayBuffer, ElementBufferObject);
        GL.BufferData(BufferTarget.ElementArrayBuffer, NumberOfVertices * sizeof(uint), indices, 
                   BufferUsageHint.DynamicRead);
    }

    public Mesh()
    {
        VertexBufferObject = GL.GenBuffer();
        GL.BindBuffer(BufferTarget.ArrayBuffer, VertexBufferObject);
        ElementBufferObject = GL.GenBuffer();
        GL.BindBuffer(BufferTarget.ElementArrayBuffer, ElementBufferObject);

        VertexArrayObject = GL.GenVertexArray();
        GL.BindVertexArray(VertexArrayObject);
        GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), 0);
        GL.EnableVertexAttribArray(0);
    }
    public virtual void Draw()
    {
        GL.BindVertexArray(VertexArrayObject);
        GL.BindBuffer(BufferTarget.ArrayBuffer, VertexBufferObject);
        GL.BindBuffer(BufferTarget.ElementArrayBuffer, ElementBufferObject);
        GL.DrawElements(PrimitiveType, NumberOfVertices, DrawElementsType.UnsignedInt, 0);

    }
}

Any help is much appreciated.

Kind regards

1 Like
2

No idea about the memory usage. However:

You need to bind the VAO before the EBO, as the GL_ELEMENT_ARRAY_BUFFER binding is stored in the current VAO; there’s no-where to store it if no VAO is bound.