Disappearing objects....

[Shaun]

I've got a model of fences and vegetation, normal stuff.... but when you view it from a certain angle, the whole thing disappears, and then reappears as if you look at it from a slightly different angle.... what is going on?!

 

[Shaun]

I think I've figured it out....
My empty LOD was showing as you view it from the angle where you're facing the backs of the double sided planes!... They obviously don't count towards the LOD calculation.... annoying as there's a lot of polys.

 

[xbuddy]

happen to me too, even a huge terminal can disappeared.

don't know why

 

[arno]

Hi,

This can happen if the bounding box of the object is wrong (too small).

 

[Shaun]

This explains why some objects, like big hangars, disappear when reaching the corner of the screen? Despite being present in 100s of pixels there.

How does one modify the bounding box?

 

[arno]

Normally GMax will calculate the bounding box correctly for you. So in most case there should not be a problem.

Is this with the FSX or FS2004 gamepack? And are the objects optimized so that the reference point is in the centre of the object.

 

[Shaun]

Ah, no they aren't, the reference point is quite far away, at the edge of my background sheet. Does this affect performance? If I put the model at 0,0 I don't know what coordinates it is...

 

[arno]

Hi,

Yes, I think having them very far from the reference point can influence the disappearing of the objects. It is much more optimal to have each object with a reference point that is roughly in the middle of the object.

You can then probably position the object with some placement tool. Or if you know the offset in meters you could calculate the position.

 

[Shaun]

Ok, I'm using the centre as the reference point now,

I have disappearing hangars also when they are passing out of view, yet these are placed in ADE, with the reference point at the centre of the object. I might put a simple box under ground that extends beyond the boundaries to try and fix this actually.

 

[lionheart]

I see this often with fences in P3D. I thought it was the sim platform doing odd things. I do not remember this happening before in FSX, though FSX did everything else crazy, lol.. (pink runways???)

 

[mjl1966]

Arno,

I have the same problem with my taxiway light models. I have created many buildings with Sketchup and ModelX conversion that work fine, so I know that process pretty well. But with these small objects, they disappear/reappear at random. Changing the view angle often brings them back. What's really odd is that only the base model disappears. The texture used to simulate the light glow does not. It stays the whole time.

My model steps are Sketchup - DAE - ModelX. I'm using both day and night textures. The model is centered on 0,0.

What are the things I need to check? You mentioned bounding box. Given than I use Sketchup - DAE, is there a way to change that?

 

[arno]

Hi,

The bounding box is automatically calculated during conversion to MDL file.

Does your model include only one light or multiple instances of the light?

 

[JRobinson]

What's really odd is that only the base model disappears. The texture used to simulate the light glow does not. It stays the whole time.

That would make me think that you've exceeded the 43690 triangle limit on a given drawcall rather than a bounding box problem. You may need to make another model that uses a renamed copy of your texture sheet and substitute that model for half of your placements.

Jim

 

[mjl1966]

Hi,

The bounding box is automatically calculated during conversion to MDL file.

Does your model include only one light or multiple instances of the light?

Hi Arno. Thanks for your reply.

There are no attached effects to the object. (I'm guessing that's what you mean by "light") The light is simulated with a semi-transparent texture on a plane - pretty much the same as you see in the various tutorials and discussions on how to make taxiway lights. It is part of the model from the beginning.

I see from what you're saying that we don't have any control over the bounding box, so that probably isn't the issue. Any other thoughts?

 

[mjl1966]

That would make me think that you've exceeded the 43690 triangle limit on a given drawcall rather than a bounding box problem. You may need to make another model that uses a renamed copy of your texture sheet and substitute that model for half of your placements.

Jim

Hi Jim. Thanks for the reply.

This is a fairly simple model made from extruded cylinders and a couple of planes. It doesn't take very many instances for the problem to occur. I placed about 30 lights last night for testing and they all disappeared/reappeared. I'll doublecheck the triangle count in ModelConverterX. I also find the idea of staggered draw calls intriguing. It increases the number of calls, which could be a framerate concern, but it is something I would never have thought of. I'll give it a shot to see what the results are.

 

[JRobinson]

So did your lights have roughly 1450 triangles according to MCX (43690/30=1456.3)? That seems impossible but if <30 placements works and the problem starts occurring at >30 placements it must be the cause. If that's the case I think I'd look into reducing the triangle count rather than adding the drawcall, I have a fairly complex taxiway light object that's 168 triangles. Do your cylinders have many unnecessary height segments? Sketchup wants to make circles with 24 sides by default and for a taxiway light you shouldn't need more than 8 so when you make your circle before you extrude it, right click and choose entity info, there you can reduce the number of sides to 6 or 8 before you start extruding, that will have a profound effect on the number of triangles in the finished model but you won't likely be able to see the difference in the sim if you "soften edges".

Jim