Sorting of blended object is incorrect in the latest dev branch

[daiwei1999]

I found EntityCollector._entryPoint and _cameraForward attribute is not updated every frame, this will cause the calculation of zIndex of RenderableListItem incorrectly which used to sort blended object.

[daiwei1999]

It's simple to produce this bug:

var cube:Mesh = new Mesh(new CubeGeometry(), new ColorMaterial(0xFF0000, 0.7));
cube.x = -100;
scene.addChild(cube);

var sphere:Mesh = new Mesh(new SphereGeometry(), new ColorMaterial(0x00FF00, 0.7));
sphere.x = 100;
scene.addChild(sphere);

If you move and rotate the camera, you can easily discover the sorting order is not always correct.

[rob-bateman]

your example does not use blending - can you post an exact test class exhibiting the problem that we can review?

[profelis]

daiwei1999 talk about transparent meshes and its sorting.

[iY0Yi]

Hey, if this issue is correct, that will be nice.

@rob-bateman
Here is the code for reproducing.
https://gist.github.com/GoroMatsumoto/5948112
Red ball always present in front of green.
Both alpha property is 1.0.
Just set alphaBlending = true;

[iY0Yi]

@daiwei1999
Can you post the code for fixing this issue? If you have.
Cheers.

[daiwei1999]

I fix the issue by only add two lines to the beginning of EntityCollector.clear method:
public function clear():void
{
_entryPoint = _camera.scenePosition;
_cameraForward = _camera.forwardVector;
_cullPlanes = _customCullPlanes ? _customCullPlanes : _camera.frustumPlanes;
....
}
This modification will update _entryPoint and _cameraForward every frame which used to calculate zIndex, and correct zIndex will be used to sort blended object correctly.

[iY0Yi]

@daiwei1999
Thank you!
Your code works with my above code. Great.

But I tested with more many meshes, and I found a little artifact of z-sorting.

for(var i:int = 0; i<500; i++)
{
    var material:ColorMaterial = new ColorMaterial(0xFFFFFF*Math.random());
    material.lightPicker = lightPicker;
    material.specular = .01;
    material.gloss = 5;
    material.alphaBlending = true;  

    var sp:Mesh = new Mesh(new SphereGeometry(400,32,32), material);
    sp.x = (Math.random()*2-1)*5000;
    sp.y = (Math.random()*2-1)*5000;
    sp.z = (Math.random()*2-1)*5000;
    view.scene.addChild(sp);
}

If faces of a mesh are intersected with other mesh's faces,
an artifact occurs there.
If you have a time for this, please confirm it with this code.

Anyway, your code improves Away3D's z-sorting problem comparatively.

Cheers.

[rob-bateman]

looks like the suggested fix works great! thanks guys

@GoroMatsumoto the artifacts you describe are a limitation of the blending system. when rendering objects this way, individual materials are rendered in a fixed order depending on their blend mode and object depth. as a result, intersecting objects are to be avoided if possible

[mariommoreno]

I've downloaded last dev, and issue still persist for me.
I'm using different meshes with TextureBitmaps.alphaBlending = true; Character one is a plane with an animated sprite sheet, dust particles are sprite3D.

Meshes are included in ObjectContainer3D and then added to scene in order to group them, if it helps. Maybe "entity.x y z" are not in global coordinates?

Any idea how to solve it?

[mariommoreno]

Yes... the relative coordinates of entities are not valid for z-ordering.
I've changed this lines in EntityCollector.applyRenderable() and now it works:

var dx:Number = _entryPoint.x - entity.x;
var dy:Number = _entryPoint.y - entity.y;
var dz:Number = _entryPoint.z - entity.z;               

var dx:Number = _entryPoint.x - entity.scenePosition.x;
var dy:Number = _entryPoint.y - entity.scenePosition.y;
var dz:Number = _entryPoint.z - entity.scenePosition.z;             

Do you know if using scenePosition affects performance?
If not, I think it must be added to dev version.

[shishenkov]

Oh man - thank you Mario 👍 the entity.scenePosition check is still not in the dev branch of aw3d but finding your post got me a solution i was trying to figure out all day yesterday - i have a complex sphere-like object constructed out of hexagonal "tiles" that are using transparent png textures and the wrong sorting order totally messed it up - i was about to call the designer to request an interface revamp to accommodate non-transparent tiles
anyway .. i compiled the latest dev version of the away 3d 4.1.4 with that fix applied
here's a link if anyone out there needs the bin only:
https://dl.dropboxusercontent.com/u/65764384/Away3d-CustomBuilds/Away3d-4.1.4-dev-20130924.swc