Wrong Z Order

[Auria]

Hi,

I believe this is a known issue, but...
1) I potentially have new information to add
2) I'd like to bump it up, since I was told that mentioning "this is for SuperTuxKart" might help prioritise the issue (yeah, I'm shamelessly using that ^^)

for reference, I think ticket https://sourceforge.net/tracker/?func=d ... tid=540676 is relevant.

See attached screenshots; we used to have a transparent parachute that could be attached behind karts ( now in our latest SVN it was replaced by a non-transparent one, which happens to look better so in the end we don't care very hard for that particular one, but still it's a bug )
The 0.6 version was using plib and displaying transparency properly. On the 0.7 development trunk, using irrLicht, there are however obvious ordering issues.

In 0.6 :

In 0.7 :


There is another spot which becomes quite problematic. We have a track with shifting sand. Z sorting issues seem to happen randomly; in my case, it seems that it's correct when I build STK in debug mode, but messed up when I build STK in release mode (no idea why).



Hope this is not too painful to correct,

-- Auria

[3DModelerMan]

I have the same problem with transparent textures. Is it running in OpenGL or D3D9, it only happens for me in D3D.

[Frank Dodd]

Have you tried it with: -

Code: Select all

smgr->getParameters()->setAttribute(scene::ALLOW_ZWRITE_ON_TRANSPARENT, true);

[hybrid]

Do the karts happen to be transparent as well. This might even be true only for the material setting, without actually having a transparent element. Otherwise, the rendering should usually be ok. Because solid meshes are rendered first.
Inn case both are transparent, the mentioned bug could fix the issue. But we're still testing the patch, so I cannot tell if it works any better, and when we can apply it to the library. But, also the mentioned scene parameter could help. This heavily depends on the actual mesh geometries.

[Auria]

Good question Hybrid; materials are left to their default type unless we flag them as having textures with alpha; and karts in the screenshots above are mostly flat (untextured) and as such are explicitely set to solid materials type.

3DModelerMan: OpenGL, we don't use DirectX

About z buffer writes, I believe we tried both options

[hybrid]

About the sand problem: Could you please post a correct screenshot as well? It's hard to tell which part is missing. However, it looks like the shadow is also clipped in this case, which means that it's not just an ordering problem. Which shaodw technique do you use?

[Auria]

Correct screenshot here


About shadow technique : a plane with a PNG texture on it

But you're right, for this particular case it seems to be something more than Z sorting

[hybrid]

It looks like parts of the kart are clipped. Do you have several separate meshes for one kart? Make sure that the bboxes are correct (enable debug render and check in these cases) and that you're using Irrlicht 1.7.1
Also, do you use octree anywhere? And how do the "sandbox" and the kart meshes intersect?

[Auria]

Do you have several separate meshes for one kart?

Yes, one for body, 4 for wheels, one for shadow

Make sure that the bboxes are correct (enable debug render and check in these cases)

I'll need to check that further; Joerg, who generally does the 3D parts, is currently on leave so I can't ask him whether we have debug render support for irrlicht - i'll need to check.

and that you're using Irrlicht 1.7.1

we are

Also, do you use octree anywhere?

yes, the static bits of the track are an octree ( m_scene_manager->addOctreeSceneNode(mesh); ), others are regular scene nodes

And how do the "sandbox" and the kart meshes intersect?

Im sorry, I don't understand what you mean

[hybrid]

What I meant is that the transparent sand is probably a separate mesh/meshbuffer, which is pretty huge. The kart might be completely inside the sand mesh, or intersects with it only partially. You could also play around with automatic culling setting and zbuffer settings to check why it really looks this strange.

[Auria]

Indeed the shifting sand is one huge mesh; so I realize this could give trouble to the z ordering code. However, since you tell me all opaque stuff is rendered first and then the transparent ones last, this still shouldn't happen; *puzzled*