OpenTK - How to achive antialiasing using accumulation buffer

问题

Im trying to achieve antialiasing using accumulation buffer, but i don't fully understand what i'm doing wrong. The only effects im getting is drop down in fps, which i know is to be expected in this method.

The jitter table is a table filled with floats to make antialiasing look smoother.

I think it's probably because setting MartixMode doesnt change UniformMatrix method i later use in drawing objects.

Here's my OnRenderFrame method:

protected override void OnRenderFrame(FrameEventArgs e)
    {
        base.OnRenderFrame(e);
        GL.Viewport(0, 0, Width, Height);
        GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
        GL.Enable(EnableCap.DepthTest);
        GL.Clear(ClearBufferMask.AccumBufferBit);

        shaders[activeShader].EnableVertexAttribArrays();
        int jitter;
        int numJitters = 4;

        double j0, j1;
        GL.Disable(EnableCap.Multisample);
        for (jitter = 0; jitter < numJitters; jitter++)
        {
            float dx, dy;
            int[] viewport = new int[4];
            GL.GetInteger(GetPName.Viewport,viewport);

            float windowWidth = viewport[2];
            float windowHeight = viewport[3];
            float frustumWidth = (float)(right - left);
            float frustumHeight = (float)(top - bottom);

            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadIdentity();
            dx = (float) jitterTable[jitter, 0] * frustumWidth / windowWidth;
            dy = (float) jitterTable[jitter, 1] * frustumHeight / windowHeight;

            GL.Frustum(left + dx, right + dx, bottom + dy, top + dy, near, far);

            GL.MatrixMode(MatrixMode.Modelview);
            GL.LoadIdentity();

            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);

            int indiceat = 0;
            foreach (Volume v in objects)
            {
                GL.UniformMatrix4(shaders[activeShader].GetUniform("modelview"), false, ref v.ModelViewProjectionMatrix);

                GL.DrawElements(BeginMode.Triangles, v.IndiceCount, DrawElementsType.UnsignedInt, indiceat * sizeof(uint));
                indiceat += v.IndiceCount;
            }
            GL.Accum(AccumOp.Accum, 1.0f / numJitters);
        }
        GL.Accum(AccumOp.Return, 1.0f);
        shaders[activeShader].DisableVertexAttribArrays();

        GL.Flush();
        SwapBuffers();
}

Also i know there are better ways to achieve antialiasing, but my task is to do it this way.

UPDATE

After some search i found a way to to use accumulation buffer with shaders. Now the part of my method where i draw looks like this: for (jitter = 0; jitter < numJitters; jitter++) {

            int indiceat = 0;
            foreach (Volume v in objects)
            {
                Matrix4 aamat = Matrix4.Identity;
                Vector3 vector3 = new Vector3((float)(jitter % 4) / (4 * Width), (float)(jitter / 4) / (4 * Height), 0.0f);                   
                Matrix4.CreateTranslation(ref vector3, out aamat);
                Matrix4 mvp = v.ModelViewProjectionMatrix * aamat;
                GL.UniformMatrix4(shaders[activeShader].GetUniform("modelview"), false, ref mvp);

                GL.DrawElements(BeginMode.Triangles, v.IndiceCount, DrawElementsType.UnsignedInt, indiceat * sizeof(uint));
                indiceat += v.IndiceCount;
            }
            GL.Accum(AccumOp.Accum, 1.0f / (float) numJitters);
        }
        GL.Accum(AccumOp.Return, 1.0f);

As you can see on screenshot it smoothes out a part of cow object,but not all of it (numJitters was set to 64 for this screenshot):

For comparison here is the same object, but with multisampling enabled:

Any idea why it smoothed out just a part of the object ?

来源：https://stackoverflow.com/questions/59363130/opentk-how-to-achive-antialiasing-using-accumulation-buffer