Updating bufferarray every frame OpenTK

Question

I am drawing an object in OpenTK that keeps changing position in each frame. For now, I keep changing the position array and buffering the new data by calling GL.BufferData. Is there a way where I can update or map to one buffer array without making a new one in every frame? I noticed that I eventually get Out Of Memory exception.

private void Drawobject(Vector3 cursorPos)
{           
    float[] cursors = new float[] { cursorPos.X-0.01f , cursorPos.Y-0.01f - 0.2f, cursorPos.Z, cursorPos.X-0.01f, cursorPos.Y-0.01f + 0.2f, cursorPos.Z, cursorPos.X-0.01f - 0.2f, cursorPos.Y-0.01f, cursorPos.Z, cursorPos.X-0.01f + 0.2f, cursorPos.Y-0.01f, cursorPos.Z };
    int VertexBufferCursor, _vao;
    VertexBufferCursor = GL.GenBuffer();
    GL.BindBuffer(BufferTarget.ArrayBuffer, VertexBufferCursor);
    GL.BufferData(BufferTarget.ArrayBuffer, cursors.Count() * sizeof(float), cursors, BufferUsageHint.StaticDraw);
    _vao = GL.GenVertexArray();
    GL.BindVertexArray(_vao);
    GL.EnableVertexAttribArray(0);
    GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), 0);
    GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
    GL.BindVertexArray(0);
    shader4.Use();
    GL.BindVertexArray(_vao);
    GL.DrawArrays(PrimitiveType.Lines, 0, 4);
    GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
    GL.BindVertexArray(0);
}

protected override void OnRenderFrame(FrameEventArgs e)
{
    Drawobject(currentMousePos);
}

score 1 · Accepted Answer · answered May 16 '20 at 17:46

Create the Vertex Array Object and the Vertex Buffer Object once at initialization:

private int VertexBufferCursor;
private int _vao;

private void Init(Vector3 cursorPos)
{           
    float[] cursors = new float[] { cursorPos.X-0.01f , cursorPos.Y-0.01f - 0.2f, cursorPos.Z, cursorPos.X-0.01f, cursorPos.Y-0.01f + 0.2f, cursorPos.Z, cursorPos.X-0.01f - 0.2f, cursorPos.Y-0.01f, cursorPos.Z, cursorPos.X-0.01f + 0.2f, cursorPos.Y-0.01f, cursorPos.Z };
    VertexBufferCursor = GL.GenBuffer();
    GL.BindBuffer(BufferTarget.ArrayBuffer, VertexBufferCursor);
    GL.BufferData(BufferTarget.ArrayBuffer, cursors.Count() * sizeof(float), cursors, BufferUsageHint.StaticDraw);
    _vao = GL.GenVertexArray();
    GL.BindVertexArray(_vao);
    GL.EnableVertexAttribArray(0);
    GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), 0);
    GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
    GL.BindVertexArray(0);
    GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
}

Update the buffer in every frame by glBufferSubData:

private void Drawobject(Vector3 cursorPos)
{           
    float[] cursors = new float[] { cursorPos.X-0.01f , cursorPos.Y-0.01f - 0.2f, cursorPos.Z, cursorPos.X-0.01f, cursorPos.Y-0.01f + 0.2f, cursorPos.Z, cursorPos.X-0.01f - 0.2f, cursorPos.Y-0.01f, cursorPos.Z, cursorPos.X-0.01f + 0.2f, cursorPos.Y-0.01f, cursorPos.Z };

    GL.BindBuffer(BufferTarget.ArrayBuffer, VertexBufferCursor);
    GL.BufferSubData(BufferTarget.ArrayBuffer, IntPtr.Zero, cursors.Count() * sizeof(float), cursors);
    GL.BindBuffer(BufferTarget.ArrayBuffer, 0);

    shader4.Use();
    GL.BindVertexArray(_vao);
    GL.DrawArrays(PrimitiveType.Lines, 0, 4);
    GL.BindVertexArray(0);
}

Updating bufferarray every frame OpenTK

1 Answers1