point sprites render smaller with MSAA samples=16 than with other settings

I recently noticed that Points-mode meshes render differently when the app is configured for 16 samples-per-pixel than when it is configured for 2, 4, 6, or 8 samples-per-pixel.

When the test app (below) is run in a 640x480 window with anti-aliasing disabled, the points p1 and p2 render as barely-touching white squares. Likewise with 2-, 4-, 6-, or 8-sample anti-aliasing. But with 16 samples, the points render as squares about half as large, so that there is a noticeable gap between them.

I doubt this relates to my GPU's maximum point sprite size, since doubling the PointSize in the mesh causes the squares to touch with 16-sample anti-aliasing.

I discovered this issue in JME version 3.2.1-stable and verified that it also occurs with 3.2.0-stable.

package mygame;

import com.jme3.app.SimpleApplication;
import com.jme3.font.BitmapText;
import com.jme3.material.Material;
import com.jme3.math.ColorRGBA;
import com.jme3.scene.Geometry;
import com.jme3.scene.Mesh;
import com.jme3.scene.VertexBuffer;
import com.jme3.util.BufferUtils;
import java.nio.FloatBuffer;

public class Main extends SimpleApplication {

    class PointMesh extends Mesh {

        PointMesh() {
            FloatBuffer fPos = BufferUtils.createFloatBuffer(3);
            fPos.put(0f).put(0f).put(0f);
            fPos.flip();
            VertexBuffer vPos = new VertexBuffer(VertexBuffer.Type.Position);
            vPos.setupData(VertexBuffer.Usage.Stream, 3, VertexBuffer.Format.Float, fPos);
            setBuffer(vPos);
            setMode(Mesh.Mode.Points);
            updateBound();
        }
    }

    public static void main(String[] args) {
        Main app = new Main();
        app.start();
    }

    @Override
    public void simpleInitApp() {
        flyCam.setEnabled(false);

        Material white6 = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
        white6.setColor("Color", ColorRGBA.White);
        white6.setFloat("PointSize", 6f);

        Mesh mesh = new PointMesh();

        Geometry p1 = new Geometry("p1", mesh);
        p1.setMaterial(white6);
        rootNode.attachChild(p1);

        Geometry p2 = new Geometry("p2", mesh);
        p2.setMaterial(white6);
        p2.setLocalTranslation(0.1f, 0.1f, 0f);
        rootNode.attachChild(p2);

        int samples = settings.getSamples();
        int height = cam.getHeight();
        int width = cam.getWidth();
        float pointSize = (Float) white6.getParam("PointSize").getValue();
        BitmapText text = new BitmapText(guiFont, false);
        String message = String.format(
                "Samples=%d Height=%d Width=%d PointSize=%.0f",
                samples, height, width, pointSize);
        text.setText(message);
        float centerX = (width - text.getLineWidth()) / 2;
        text.setLocalTranslation(centerX, height, 0f);
        guiNode.attachChild(text);
    }
}

INFO: OpenGL Renderer Information

• Vendor: NVIDIA Corporation
• Renderer: GeForce GT 545/PCIe/SSE2
• OpenGL Version: 4.6.0 NVIDIA 388.73
• GLSL Version: 4.60 NVIDIA
• Profile: Compatibility

Start with the supplied Java reproducer in Main and run it at 640x480 with anti-aliasing set to disabled, 2, 4, 6, 8, and 16 samples. Compare the spacing and apparent size of the two point sprites; no repository file or test is named, so completion would require locating the rendering path and verifying consistent point-sprite sizing across these settings.