Lemur IconComponent issue with transparent icons

Ali_RS · January 18, 2022, 9:52am

Hi

Curious why “AlphaDiscardThreshold” is needed for IconComponents? And is there a way to turn it off globally for IconComponents in the style?

github.com

jMonkeyEngine-Contributions/Lemur/blob/7ca8f1ee22fedec4979b6548038d3b98efa8b122/src/main/java/com/simsilica/lemur/component/IconComponent.java#L427

    
      
          if( material == null ) {
              material = GuiGlobals.getInstance().createMaterial(lit);
              material.setColor(color);
              material.setTexture(image);
          
          
    material.getMaterial().getAdditionalRenderState().setBlendMode(BlendMode.Alpha);
              // AlphaTest and AlphaFalloff are deprecated in favor of the material
              // parameter... in fact in current JME there are no-ops.
              //material.getMaterial().getAdditionalRenderState().setAlphaTest(true);
              //material.getMaterial().getAdditionalRenderState().setAlphaFallOff(0.01f);
              material.getMaterial().setFloat("AlphaDiscardThreshold", 0.1f);
          }
          
          
icon.setMaterial(material.getMaterial());
          
          
// Leave it invisible until the first time we are reshaped.
          // Without this, there is a noticeable one-frame jump from
          // 0,0,0 to it's proper position.
          icon.setCullHint(CullHint.Always);
          
          
// Just in case but it should never happen

UI icons might have a transparent shadow on them, specifying “AlphaDiscardThreshold” will eliminate the shadow.

See shadows in this Lemur Label example:

Without “AlphaDiscardThreshold”:
Screenshot_2022-01-18_13-07-19

With “AlphaDiscardThreshold”:
Screenshot_2022-01-18_13-09-07

Note, the blue background is the skybox.

pspeed · January 19, 2022, 3:08am

I don’t know. It seems like layering would have taken care of any ordering z-buffer issues… so it might be a hold-over from something ancient.

No… at the moment this would have to be reset after the icon component is created.

…at least until the problem is fixed properly.

Ali_RS · January 27, 2022, 5:20am

Looks like it is also used in “QuadBackgroundComponent” and “GuiGlobals.loadFont” too.

pspeed · January 27, 2022, 9:42am

Do you build Lemur from source right now or just use a standard release?

Ali_RS · January 27, 2022, 9:50am

Build it from the source.

pspeed · January 27, 2022, 12:10pm

Cool. I’ll see if I can fix it in the next few days.

pspeed · January 28, 2022, 10:25pm

I’ve just checked in a fix that should solve your problem… though it may slightly create problems for others. At least the value is not hard-coded anymore.

Basically, I allow alpha discard to be set on QuadBackgroundComponent and IconComponent and it now defaults to 0 instead of 0.1. (May be a breaking change for some… though even in the demo code I found it to have fixed a problem I didn’t even know was there.)

Lemur got its start from the UI code for the second iteration of the Mythruna engine and all of those UIs were 3D. Alpha discard was kind of important in that case. (Though that was also before layers were added to enforce local sort ordering.) For 2D UIs, alpha discard should not even be necessary because the JME Gui bucket always sorts back to front on hard Z. There is no room for “which angle am I looking” style interpretation messing things up. And I think for the 3D case, most issues will be resolvable with layering since even a 3D UI will probably have rectangular (or at least full-coverage) backgrounds on the base layer.

This new alphaDiscard is only “stylable” in the sense that the IconComponent or QuadBackgroundComponent themselves are stylable. If application code is setting the icon directly for some GUI element then they will have to be aware of it and set it if they care to. But even that seems best as one icon might require one value while a different icon requires another.

Ali_RS · January 29, 2022, 5:41am

Thanks!

Is this the same as clearing the param?

Also, is this one left out intentionally?

github.com

jMonkeyEngine-Contributions/Lemur/blob/7f3c3fb159f8864968d1c15113b6d2a6cb92ea82/src/main/java/com/simsilica/lemur/GuiGlobals.java#L287


      
           *  Goes through all of the font page materials and sets
           *  alpha test and alpha fall-off.
           */
          public void fixFont( BitmapFont font ) {
              for( int i = 0; i < font.getPageSize(); i++ ) {
                  Material m = font.getPage(i);
                  // AlphaTest and AlphaFalloff are deprecated in favor of the material
                  // parameter... in fact in current JME there are no-ops.
                  //m.getAdditionalRenderState().setAlphaTest(true);
                  //m.getAdditionalRenderState().setAlphaFallOff(0.1f);
                  m.setFloat("AlphaDiscardThreshold", 0.1f);
              }
          }
          
          private Texture getTexture( Material mat, String name ) {
              MatParam mp = mat.getParam(name);
              if( mp == null ) {
                  return null;
              }
              return (Texture)mp.getValue();
          }

pspeed · January 29, 2022, 9:56am

Is it causing you issue?

Fonts are one of those ones that are super hard to fix at the application level and are pretty much always jacked up whenever used in 3D without discard. The fixFont() method exists for no other purpose.

pspeed · January 29, 2022, 9:58am

No. I looked for some method to remove a parameter but “clear” was the one name I didn’t think of.

Given that alpha discard is wired to a define, I believe it’s essentially the same as not setting it when it’s zero. But it is an oversight that I didn’t clear it.

Ali_RS · January 29, 2022, 11:43am

No, but it could be an issue if the font has shadows.

pspeed · January 29, 2022, 12:45pm

You will find that bitmap fonts don’t like shadows. The letter quads overlap and things potentially get really janky for anything that goes outside the letter borders.

…moreover, the shadows would also become colored.

There are numerous reasons that shadows won’t work well built into the font… and coincidentally they are very similar reasons to why alpha discard is pretty much required for rendering the fonts in 3D.