[SOLVED] setting RenderState.BlendMode.Off on ParticleEmitter

capdevon · December 24, 2021, 4:04pm

Hi,
experimenting with particle effects, I noticed that by changing the default ‘BlendMode’ of the ‘particle material’ from Off to Alpha and then back to Off, something seems to break.

In short, setting the BlendMode.Off after changing it once, the effect no longer works correctly. Could this be a bug?

-

Here is the test case:

package com.test.main;

import com.jme3.app.SimpleApplication;
import com.jme3.effect.ParticleEmitter;
import com.jme3.effect.ParticleMesh;
import com.jme3.light.DirectionalLight;
import com.jme3.material.Material;
import com.jme3.material.RenderState.BlendMode;
import com.jme3.math.ColorRGBA;
import com.jme3.math.FastMath;
import com.jme3.math.Vector3f;
import com.jme3.renderer.queue.RenderQueue;
import com.jme3.system.AppSettings;

/**
 * 
 * @author capdevon
 */
public class Test_BlendModeIssue extends SimpleApplication {

	private ParticleEmitter emit;
	private float angle = 0;
	private float timer;
	private float refreshRate = 1f;
	private int mIndex = 0;
	private BlendMode[] modes = { BlendMode.Off, BlendMode.Alpha };

	/**
	 * 
	 * @param args
	 */
	public static void main(String[] args) {
		AppSettings settings = new AppSettings(true);
		settings.setResolution(800, 600);

		Test_BlendModeIssue app = new Test_BlendModeIssue();
		app.setShowSettings(false);
		app.setPauseOnLostFocus(false);
		app.setSettings(settings);
		app.start();
	}

	@Override
	public void simpleInitApp() {
		flyCam.setDragToRotate(true);
		flyCam.setMoveSpeed(20);

		viewPort.setBackgroundColor(ColorRGBA.DarkGray);

/* --not required
		DirectionalLight sun = new DirectionalLight();
		sun.setDirection((new Vector3f(-0.5f, -0.5f, -0.5f)).normalizeLocal());
		sun.setColor(ColorRGBA.White);
		rootNode.addLight(sun);
*/
		createParticleEmitter();
	}

	@Override
	public void simpleUpdate(float tpf) {
		timer += tpf;
		if (timer > refreshRate) {
			timer = 0;
			mIndex = (mIndex + 1) % modes.length;
			BlendMode bm = modes[mIndex];
			fpsText.setText("BlendMode: " + bm.toString());
			emit.getMaterial().getAdditionalRenderState().setBlendMode(bm);
		}

		angle += tpf;
		angle %= FastMath.TWO_PI;
		float x = FastMath.cos(angle) * 2;
		float y = FastMath.sin(angle) * 2;
		emit.setLocalTranslation(x, 0, y);
	}

	private void createParticleEmitter() {
		emit = new ParticleEmitter("Emitter", ParticleMesh.Type.Triangle, 300);
		Material mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md");
		mat.setTexture("Texture", assetManager.loadTexture("Effects/Smoke/Smoke.png"));
		emit.setGravity(0, 0, 0);
		emit.getParticleInfluencer().setVelocityVariation(1);
		emit.getParticleInfluencer().setInitialVelocity(new Vector3f(0, .5f, 0));
		emit.setLowLife(1);
		emit.setHighLife(1);
		emit.setImagesX(15);
		emit.setMaterial(mat);
		rootNode.attachChild(emit);

		System.out.println("Default BlendMode: " + mat.getAdditionalRenderState().getBlendMode());
	}
}

Edit:

Right, directional light does not affect the test.

1000ml · December 24, 2021, 4:38pm

Also happens when setting it directly to Off without setting it to something else first.
The DirectionalLight doesn’t seem involved.

quickly tested with jme 3.3.2 stable, 3.4.1 stable
3.5.0-beta4 had problems finding liblwjgl.so

sgold · December 27, 2021, 10:22am

@capdevon and @1000ml:

Without knowing the root causes of these behaviors, it’s hard to decide whether they are bugs or not.

Since it’s been 3 days and the root causes are still (as far as I know) unknown, please open issues at GitHub for both behaviors:

the effect looking different and
inability to find “liblwjgl.so” (on which platform?)

Ali_RS · December 27, 2021, 10:49am

@capdevon does it happen also with other material types like Lighting.j3md or only happens with Particle.j3md?

capdevon · December 27, 2021, 10:56am

Hi Stephen, here it is:

github.com/jMonkeyEngine/jmonkeyengine

ParticleEmitter does not work correctly with RenderState.BlendMode.Off.

opened 10:51AM - 27 Dec 21 UTC

capdevon

I opened this issue to keep track of the forum discussion: https://hub.jmonkeye…ngine.org/t/problem-setting-renderstate-blendmode-off-on-particleemitter/45215 Changing the default "BlendMode" of the "particle material" from Off to another and then back to Off, something seems to break. Also happens when setting it directly to Off without setting it to something else first. Here is the test case: ```java package com.test.main; import com.jme3.app.SimpleApplication; import com.jme3.effect.ParticleEmitter; import com.jme3.effect.ParticleMesh; import com.jme3.light.DirectionalLight; import com.jme3.material.Material; import com.jme3.material.RenderState.BlendMode; import com.jme3.math.ColorRGBA; import com.jme3.math.FastMath; import com.jme3.math.Vector3f; import com.jme3.renderer.queue.RenderQueue; import com.jme3.system.AppSettings; /** * * @author capdevon */ public class Test_BlendModeIssue extends SimpleApplication { private ParticleEmitter emit; private float angle = 0; private float timer; private float refreshRate = 1f; private int mIndex = 0; private BlendMode[] modes = { BlendMode.Off, BlendMode.Alpha }; /** * * @param args */ public static void main(String[] args) { AppSettings settings = new AppSettings(true); settings.setResolution(800, 600); Test_BlendModeIssue app = new Test_BlendModeIssue(); app.setShowSettings(false); app.setPauseOnLostFocus(false); app.setSettings(settings); app.start(); } @Override public void simpleInitApp() { flyCam.setDragToRotate(true); flyCam.setMoveSpeed(20); viewPort.setBackgroundColor(ColorRGBA.DarkGray); createParticleEmitter(); } @Override public void simpleUpdate(float tpf) { timer += tpf; if (timer > refreshRate) { timer = 0; mIndex = (mIndex + 1) % modes.length; BlendMode bm = modes[mIndex]; fpsText.setText("BlendMode: " + bm.toString()); emit.getMaterial().getAdditionalRenderState().setBlendMode(bm); } angle += tpf; angle %= FastMath.TWO_PI; float x = FastMath.cos(angle) * 2; float y = FastMath.sin(angle) * 2; emit.setLocalTranslation(x, 0, y); } private void createParticleEmitter() { emit = new ParticleEmitter("Emitter", ParticleMesh.Type.Triangle, 300); Material mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md"); mat.setTexture("Texture", assetManager.loadTexture("Effects/Smoke/Smoke.png")); emit.setGravity(0, 0, 0); emit.getParticleInfluencer().setVelocityVariation(1); emit.getParticleInfluencer().setInitialVelocity(new Vector3f(0, .5f, 0)); emit.setLowLife(1); emit.setHighLife(1); emit.setImagesX(15); emit.setMaterial(mat); rootNode.attachChild(emit); System.out.println("Default BlendMode: " + mat.getAdditionalRenderState().getBlendMode()); } } ```

capdevon · December 27, 2021, 11:15am

I have not noticed any malfunctions with Lighiting.j3md

capdevon · December 27, 2021, 12:09pm

I tried to understand more, in the Particle.j3md file, all RenderState{} blocks have BlendMode.AlphaAdditive by default.

github.com

jMonkeyEngine/jmonkeyengine/blob/master/jme3-core/src/main/resources/Common/MatDefs/Misc/Particle.j3md#L38

    
      
              FragmentShader GLSL100 GLSL120 GLSL150 : Common/MatDefs/Misc/Particle.frag

          

              WorldParameters {

                  WorldViewProjectionMatrix

                  WorldViewMatrix

                  WorldMatrix

                  CameraPosition

              }

          

              RenderState {

                  Blend AlphaAdditive

                  DepthWrite Off

                  PointSprite On

              }

          

              Defines {

                  USE_TEXTURE : Texture

                  POINT_SPRITE : PointSprite

              }

          }

The javadoc of the RenderState class suggests using the following modes for particle effects:

Additive
AlphaAdditive

github.com

jMonkeyEngine/jmonkeyengine/blob/master/jme3-core/src/main/java/com/jme3/material/RenderState.java#L290

    
      
           * <p>

           * Result = Source Color + (Dest Color * (1 - Source Alpha) ) -&gt; (GL_ONE, GL_ONE_MINUS_SRC_ALPHA)

           */

          PremultAlpha,

          /**

           * Additive blending that is multiplied with source alpha.

           * For use with glows and particle emitters.

           * <p>

           * Result = (Source Alpha * Source Color) + Dest Color -&gt; (GL_SRC_ALPHA, GL_ONE)

           */

          AlphaAdditive,

          /**

           * Color blending, blends in color from dest color

           * using source color.

           * <p>

           * Result = Source Color + (1 - Source Color) * Dest Color -&gt; (GL_ONE, GL_ONE_MINUS_SRC_COLOR)

           */

          Color,

          /**

           * Alpha blending, interpolates to source color from dest color

           * using source alpha.

It is probably correct that particle effects do not work correctly with BlendMode.Off

1000ml · December 27, 2021, 6:04pm

That makes sense. The additive blending modes are order-independent. For other modes, in order for blending to look good, the fragments need to be sorted back-to-front. Sorting lots of moving particles every frame is costly.

Now since the blending mode is initialized to AlphaAdditive, I think this is expected behavior.

What I find suspicious though, is that mat.getAdditionalRenderState().getBlendMode() doesn’t reflect the initial value. After creating a Material with Particle.j3md it returns BlendMode.Off.

capdevon · December 27, 2021, 6:27pm

I have some suspicions about it too, but i don’t know if this is a deliberate behavior.

sgold · December 27, 2021, 7:04pm

Where does the value get changed?

capdevon · December 27, 2021, 7:09pm

maybe here

github.com

jMonkeyEngine/jmonkeyengine/blob/master/jme3-core/src/main/java/com/jme3/material/Material.java#L893

    
      
          /**

           * Returns true if the type is Buffer Object's type.

           *

           * @param type the material parameter type.

           * @return true if the type is Buffer Object's type.

           */

          private boolean isBO(final VarType type) {

              return type == VarType.BufferObject;

          }

          

          private void updateRenderState(RenderManager renderManager, Renderer renderer, TechniqueDef techniqueDef) {

              if (renderManager.getForcedRenderState() != null) {

                  renderer.applyRenderState(renderManager.getForcedRenderState());

              } else {

                  if (techniqueDef.getRenderState() != null) {

                      renderer.applyRenderState(techniqueDef.getRenderState().copyMergedTo(additionalState, mergedRenderState));

                  } else {

                      renderer.applyRenderState(RenderState.DEFAULT.copyMergedTo(additionalState, mergedRenderState));

                  }

              }

          }

sgold · January 17, 2022, 9:19pm

I’ve analyzed issue 1724, and I think I know what’s going on. @capdevon please take a look.

capdevon · January 19, 2022, 3:27pm

Hi Stephen, sorry for the delay, but I’ve had problems with the pc these days. Thank you for the detailed analysis, the behavior is now clearer. Do you suggest closing the issue or leaving it open?

sgold · January 19, 2022, 6:08pm

Do you suggest closing the issue or leaving it open?

That depends what your needs are. As pointed out in the issue discussion, there’s no mechanism (short of reflection) to reset a RenderState back to its original state. So if you’ve got an application that needs that functionality, we might follow up with an enhancement PR.

On the other hand, if it’s sufficient to return the emitter back to its original appearance, the following should suffice

   emit.getMaterial().getAdditionalRenderState().setBlendMode(BlendMode.AlphaAdditive);

and we can close both the issue and this topic.

I’d like your input.

capdevon · January 20, 2022, 8:18pm

I have written a test case which shows a lot more information.
If I understand correctly, the additional RenderState allows you to permanently overwrite the BlendMode defined in the j3md file. Until this happens, the BlendMode value and the one defined in the Technique block of the j3md file may differ at runtime. (see example)
Honestly, I can’t think of a case where it might be necessary to restore the initial state. My goal was to tweak the BlendMode at runtime to see the visual effect of each mode. There are no bugs in this and everything works fine. Maybe we can think about it in the future. What do you think?

New test case:

package com.test.main;

import com.jme3.app.SimpleApplication;
import com.jme3.effect.ParticleEmitter;
import com.jme3.effect.ParticleMesh;
import com.jme3.font.BitmapFont;
import com.jme3.font.BitmapText;
import com.jme3.input.KeyInput;
import com.jme3.input.controls.ActionListener;
import com.jme3.input.controls.KeyTrigger;
import com.jme3.material.Material;
import com.jme3.material.MaterialDef;
import com.jme3.material.RenderState.BlendMode;
import com.jme3.material.Technique;
import com.jme3.material.TechniqueDef;
import com.jme3.math.ColorRGBA;
import com.jme3.math.FastMath;
import com.jme3.math.Vector3f;
import com.jme3.system.AppSettings;

/**
 *
 * @author capdevon
 */
public class Test_BlendModeIssue extends SimpleApplication implements ActionListener {

    private ParticleEmitter emit;
    private float angle = 0;
    private int mIndex = 0;
    private BlendMode[] modes = BlendMode.values();
    private BitmapText hud;

    /**
     *
     * @param args
     */
    public static void main(String[] args) {
        AppSettings settings = new AppSettings(true);
        settings.setResolution(800, 600);

        Test_BlendModeIssue app = new Test_BlendModeIssue();
        app.setShowSettings(false);
        app.setPauseOnLostFocus(false);
        app.setSettings(settings);
        app.start();
    }

    @Override
    public void simpleInitApp() {
        flyCam.setDragToRotate(true);
        flyCam.setMoveSpeed(20);
        viewPort.setBackgroundColor(ColorRGBA.DarkGray);

        hud = createTextUI(ColorRGBA.Blue, 20, 15);

        createParticleEmitter();

        inputManager.addMapping("NextBlendMode", new KeyTrigger(KeyInput.KEY_SPACE));
        inputManager.addListener(this, "NextBlendMode");
    }

    private void createParticleEmitter() {
        emit = new ParticleEmitter("Emitter", ParticleMesh.Type.Triangle, 300);
        Material mat = new Material(assetManager, "Common/MatDefs/Misc/Particle.j3md");
        mat.setTexture("Texture", assetManager.loadTexture("Effects/Smoke/Smoke.png"));
        emit.setGravity(0, 0, 0);
        emit.getParticleInfluencer().setVelocityVariation(1);
        emit.getParticleInfluencer().setInitialVelocity(new Vector3f(0, .5f, 0));
        emit.setLowLife(1);
        emit.setHighLife(1);
        emit.setImagesX(15);
        emit.setMaterial(mat);
        rootNode.attachChild(emit);
    }

    @Override
    public void simpleUpdate(float tpf) {

        BlendMode blendMode = emit.getMaterial().getAdditionalRenderState().getBlendMode();
        fpsText.setText("AdditionalRenderState.BlendMode: " + blendMode);

        printTechniqueDefs();

        angle += tpf;
        angle %= FastMath.TWO_PI;
        float x = FastMath.cos(angle) * 2;
        float y = FastMath.sin(angle) * 2;
        emit.setLocalTranslation(x, 0, y);
    }

   private void printTechniqueDefs() {
        
        StringBuilder sb = new StringBuilder();
        MaterialDef matDef = emit.getMaterial().getMaterialDef();
        
        for (String name : matDef.getTechniqueDefsNames()) {
            for (TechniqueDef technique : matDef.getTechniqueDefs(name)) {

                BlendMode bm = null;
                if (technique.getRenderState() != null) {
                    bm = technique.getRenderState().getBlendMode();
                }

                sb.append("TechniqueDef=");
                sb.append(name);
                sb.append(", BlendMode=");
                sb.append(bm);
                sb.append("\n");
            }
        }

        Technique tech = emit.getMaterial().getActiveTechnique();
        String activeTech = "ActiveTechnique: ";
        if (tech != null) {
            activeTech += tech.getDef().getName();
        }

        hud.setText(sb.toString() + activeTech);
    }

    private BitmapText createTextUI(ColorRGBA color, float xPos, float yPos) {
        BitmapFont font = assetManager.loadFont("Interface/Fonts/Console.fnt");
        BitmapText bmp = new BitmapText(font);
        bmp.setSize(font.getCharSet().getRenderedSize() * 1.2f);
        bmp.setLocalTranslation(xPos, settings.getHeight() - yPos, 0);
        bmp.setColor(color);
        guiNode.attachChild(bmp);
        return bmp;
    }

    @Override
    public void onAction(String name, boolean isPressed, float tpf) {
        if (name.equals("NextBlendMode") && isPressed) {
            mIndex = (mIndex + 1) % modes.length;
            BlendMode blendMode = modes[mIndex];
            emit.getMaterial().getAdditionalRenderState().setBlendMode(blendMode);
        }
    }
}

sgold · January 20, 2022, 8:26pm

What do you think?

I think we can close issue 1724. Thanks.

capdevon · January 20, 2022, 8:29pm

I agree with you. Thanks for the support.