RFX features questions

abaser

Well-known member
For wheel C meshes, I'll usually take the center row of polys of the wheel and duplicate them. I'll then cap the sides and scale the width to match the width of the tire. I don't try to match the curvature of the tread because you'll never notice that it's off in the sim. To be honest, I've got a few models up that don't even have a collision mesh at all and I can't tell any ill affects from it. They were my earlier models so the newer RF versions may reflect otherwise.
 

technoid

Well-known member
For wheel C meshes, I'll usually take the center row of polys of the wheel and duplicate them. I'll then cap the sides and scale the width to match the width of the tire. I don't try to match the curvature of the tread because you'll never notice that it's off in the sim. To be honest, I've got a few models up that don't even have a collision mesh at all and I can't tell any ill affects from it. They were my earlier models so the newer RF versions may reflect otherwise.
None of my older models had a collision mesh, RF 7.5 or RF-8 doesn't require it. But RF-X does and the first plane I tried without a collision mesh got terrible frame rates until I added a collision mesh for it. That's a pretty good idea of duplicating the center two polys and capping it, but it seems what I did will work the same. I didn't curve the c. mesh because I thought it needed it I just did it to make it more like the real tire since I was adding so many triangles to it. I checked two of the Planes that's built into RF-X and one had 220 triangles and the other had 240 triangles for the collision mesh for all of the tires. And since you can't see what the c. mesh looks like I just curved it to mimic the tire not knowing what they did.

So a question. Does the collision mesh act as a solid part in the graphics engine, or is it a mesh so it has holes for something to stick through? Like the tire getting stuck in RF-X and the plane won't move. Then if the mesh is closer (more triangles) the tire doesn't get stuck because the holes are smaller and what's on the surface doesn't stick into the mesh and cause it to stick.
 

Bill Stuntz

Member
Probably a stupid question/suggestion since I'm not a builder:
Is the collision mesh aerodynamically/physically significant? For instance, is it the tire that actually rolls the ground? Or does the collision mesh lift the tire off the ground? If it's the mesh, would making the mesh slightly smaller than the tire allow the rounder tire to contact the ground & roll more smoothly?
 

abaser

Well-known member
The collision mesh is just as it sounds. It's a shell put in place over the visual model to define the contact points of the mesh it's assigned to. Take my Toucan for example. The tail breaks off when you nose it in the ground. This happens because I extended a point of the collision mesh out in front of the spinner.

With wheels, you want to match the diameter as close to the tire itself because that's what controls the impact of the tire. If your Cmesh is square, your round wheel will roll as if it's a cube and bounce all over the place. Want to see something really fun? have the Cmesh pivot reversed. Your wheel will look as if it's rolling backwards.
 

Bill Stuntz

Member
Thank you for the explanation. That's about what I thought, but I wasn't sure.

Am I correct in assuming that the collision mesh is not involved aerodynamically?

Since a collision mesh apparently isn't required except in RF-X, what happens when an aircraft doesn't have one? Does it just remain intact in a crash? How do I know whether an aircraft does or doesn't have a collision mesh? Why would the lack of one decrease the frame rate in RF-X? More contact points to calculate in the more detailed structure? At least I assume that the structure is more detailed than the collision mesh. Does the collision mesh simplify the calculations?
 

abaser

Well-known member
Thank you for the explanation. That's about what I thought, but I wasn't sure.

Am I correct in assuming that the collision mesh is not involved aerodynamically?

Since a collision mesh apparently isn't required except in RF-X, what happens when an aircraft doesn't have one? Does it just remain intact in a crash? How do I know whether an aircraft does or doesn't have a collision mesh? Why would the lack of one decrease the frame rate in RF-X? More contact points to calculate in the more detailed structure? At least I assume that the structure is more detailed than the collision mesh. Does the collision mesh simplify the calculations?
I'll try to answer what I know.

Aerodynamics is set in the editor and controlled by the parameters set there. So the Cmesh has nothing to do with that.

Usually, if the model doesn't have one there's no ill effects other than parts may sink into the ground after a crash. That can be interesting to watch.

The model can still break apart on impact if there isn't a Cmesh. The only thing a Cmesh affects is telling RF where to make contact with the model.

And yes, the Cmesh is far less detailed than the visuals. You have a 1500 poly limit for all of the collision meshes combined. I've got that much in my tail gear on my Citabria.
 

technoid

Well-known member
I have the T-28C in my hanger now, thanks for the download, that 9 cylinder radial looks great and the plane fly's perfect. (already removed the glue from the front wheel)
Lets hope Jeremy's high poly count fix will solve this problem for you.
Now back to flying, and looking for something I can get that tailhook latched onto!!! there must be a phone line around somewhere.:):):)
asj5547

Here's a new beta for you to try out. The first pass of increasing the triangle count of all the tires collision mesh really didn't seem to help, some maybe but not much. But Jeremy said they had problems when the poly count was too low so I went back and added an angle cut for all the segments in the collision mesh and also made the nose tire 1 inch wide instead of .82 inch wide. Adding the cross cut to all the segments doubled the poly count while leaving the triangle count the same, and it seemed to help quite a bit to me. It's still not perfect but the sticks seem to be way down and a short burst of the throttle seems to unstick it. So if you would please give this a try on several airports and let me know what you think. Thanks for your help on this.

Beta with improved collision mesh for all tires and nose tire is wider. Oh I upped the braking some to 90% on the main gear and 5% on the nose gear. The nose gear didn't have any braking and the main gear was 80%. I also uploaded pictures of the 1st way I did the improved collision mesh and a 2nd picture of how I added the extra poly in each segment. That's the way the tires are too.
 

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abaser

Well-known member
RF automatically triangulates your 4 sided polys so what you did didn't do anything for the poly count as far as RF sees it. At least that's the way it used to be. If RFX has a problem with what you show then it's something they need to take care of on their end. None of my wheel meshes are that detailed or high poly and I've never seen an issue.
 

technoid

Well-known member
RF automatically triangulates your 4 sided polys so what you did didn't do anything for the poly count as far as RF sees it. At least that's the way it used to be. If RFX has a problem with what you show then it's something they need to take care of on their end. None of my wheel meshes are that detailed or high poly and I've never seen an issue.
I know about the triangulate deal but what I did made a major difference in RF-X so it did something. I'm just trying to do anything I can to make the plane better in RF-X before I release it. And yeah, all the cmesh for tires I've done in the past is very simple compared to this.. but that was for RF 7.5. Anyway what I did made a major change in RF-X for me and I'd be able to go with what I've done to improve it in RF-X and feel people could fly the plane okay. But before the sticks were terrible. But right now I'm waiting to see how it works for asj5547 before I go with it. I don't want to lower the rolling resistance way down it caused the plane to roll as soon as it loaded for me.
 

abaser

Well-known member
That's odd. I always assumed RF did just what you did so I wouldn't think it would do anything. I don't have X though so it might do something completely different.
 

technoid

Well-known member
That's odd. I always assumed RF did just what you did so I wouldn't think it would do anything. I don't have X though so it might do something completely different.
There could be a difference in how the cmesh is handled in the graphics engine using a rendered only angle poly and a hard poly caused by an actual edge. Dunno, just guessing. Yes the rectangle is split to render it but without a real edge the engine may not see it as something to collide with.
 

asj5547

Well-known member
I know about the triangulate deal but what I did made a major difference in RF-X so it did something. I'm just trying to do anything I can to make the plane better in RF-X before I release it. And yeah, all the cmesh for tires I've done in the past is very simple compared to this.. but that was for RF 7.5. Anyway what I did made a major change in RF-X for me and I'd be able to go with what I've done to improve it in RF-X and feel people could fly the plane okay. But before the sticks were terrible. But right now I'm waiting to see how it works for asj5547 before I go with it. I don't want to lower the rolling resistance way down it caused the plane to roll as soon as it loaded for me.
Just rolled the T-28c slowly down the runway and applied the brakes, left mains wheel grabbed again just as the plane was stopping, give it throttle to break free.
 

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abaser

Well-known member
I see the wheel is sunk into the surface a bit. Just a question. Is there an option to turn scenery objects on and off? I had a similar thing happen in 7.5 where when objects were off, the stripes on the runway would go away. When this happened it created holes in the runway and the wheels would fall off in them and stop the plane when you got to the edge of the stripe.
 

technoid

Well-known member
I see the wheel is sunk into the surface a bit. Just a question. Is there an option to turn scenery objects on and off? I had a similar thing happen in 7.5 where when objects were off, the stripes on the runway would go away. When this happened it created holes in the runway and the wheels would fall off in them and stop the plane when you got to the edge of the stripe.
I don't know next time I start RF-X I'll look around, but I don't remember seeing anything like that. I went back and flattened the top of the tire collision mesh again thinking maybe a totally level contact area might make a difference but it didn't seem to change it to me. It's better now than it was but definitely not perfect.

One other thing that bothers me is, there's a big difference in what value it takes to make the canopy just a bit visible between RF-8 and RF-X so the canopy looks okay in RF-8 but you have a hard time seeing it in RF-X so it's almost like it isn't there.
 

asj5547

Well-known member
I don't know next time I start RF-X I'll look around, but I don't remember seeing anything like that. I went back and flattened the top of the tire collision mesh again thinking maybe a totally level contact area might make a difference but it didn't seem to change it to me. It's better now than it was but definitely not perfect.

One other thing that bothers me is, there's a big difference in what value it takes to make the canopy just a bit visible between RF-8 and RF-X so the canopy looks okay in RF-8 but you have a hard time seeing it in RF-X so it's almost like it isn't there.
I have tried the T-28C (this is the latest beta version, download today) in Meadowland and Flight School airports, adjusted rolling resistance from 100% working down to 10% and sticks at every level, sometimes just a little throttle will break it free, but once it stuck so bad at 20% it snapped the front wheel off.
I will try turning off the runway stripes and let you know the effect.'
Question, do your Great Lakes Trainer and Great Lakes Special have collision mesh or the same type of wheels, because they both roll flawlessly.
 
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asj5547

Well-known member
Is this a problem with the brakes??? I know they are not actual 'brakes' but an inferred physics value programmed in to the model.
I get the same "glued in place" aircraft behavior when I hold full down elevator and apply throttle, (that I expect) as to when the aircraft sticks after applying and releasing the brakes during taxi maneuvers.
Your biplanes that I fly do not have brakes and they taxi perfectly.
 
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