Celestia Forums

I have been reading a tutorial by rthorvald on how to graft a CMOD landscape model onto a virtual texture seamlessly http://forum.celestialmatters.org/viewtopic.php?t=36 and had a question about filling the base of a model.

From rthorvald's tutorial this is what I'm talking about.

2. Fill the hole under your top mesh!
Make sure the normals of the bottom point outwards. This we do
to minimize depht-sorting issues in Celestia.



How do you fill a mesh like that? I've been trying to figure out how to do this in anim8tor for a long time but with no luck. I tried the "fill hole" feature but the rules on being able to do this are so restrictive that it's impossible to do it on the bottom of a complex mesh such as a mountain or hill. Does anybody know how to fill the base of mesh?

If the terrain start from a plane, from an height field or from whatelse sculpting methods, the bottom of the mesh is "filled" nonetheless, being a polygon. It shouldn't "filled" whether the terrain were made, at least, from a collection of tassellating polylines (DXF points union etc.). But: what behaviour do you get with your model?

The mountains are always hollow and never have a bottom to them. When I place one on the surface of a planet where there is a VT two things happen. I get ugly seams but worst of all I get very badly jittering textures.

Here's an example. http://www.youtube.com/watch?v=x56nocoSbB4

With Anim8or, you can use "point edit" to cover the open bottom side of a mound: select the surrounding lines, then select "fill holes" to create the new surface. If the open area is too irregular, you might have to add connecting edges and fill the surface a part at a time.

To add an edge:
1. select point edit
2. select view points
3. select add edge
4. select and hold down left-mouse-button on initial point
5. release left-mouse-button on end point (it'll turn red when the cursor is close enough)

Then drag-select the edges of the new hole

Then select the Edit menu item "fill holes" -- which adds a surface if the selected edges are connected.

Thank you Selden. I'm curious, will any of this help prevent or minimize the odd jittering that happens when placing a model on a planet's surface?

Reiko wrote:Thank you Selden. I'm curious, will any of this help prevent or minimize the odd jittering that happens when placing a model on a planet's surface?

I think this "fix" won't do anything at all for the flickering.

Celestia has always had problems drawing two surfaces which are both very close and parallel to one another. I don't know if it's a problem in Celestia or in the way the graphics hardware works. I've seen it in models that I've made. In order to avoid it, you have to eliminate one of the adjacent surfaces, but you can't do that with Celestia's built-in spheres. In other words, you'd have to provide your own sphere for the planet's surface with a hole for the "real" model to fit into.

selden wrote:

Reiko wrote:Thank you Selden. I'm curious, will any of this help prevent or minimize the odd jittering that happens when placing a model on a planet's surface?

I think this "fix" won't do anything at all for the flickering.

Celestia has always had problems drawing two surfaces which are both very close and parallel to one another. I don't know if it's a problem in Celestia or in the way the graphics hardware works. I've seen it in models that I've made. In order to avoid it, you have to eliminate one of the adjacent surfaces, but you can't do that with Celestia's built-in spheres. In other words, you'd have to provide your own sphere for the planet's surface with a hole for the "real" model to fit into.

I found this problem doesn't happen when I put an addon mesh next to another addon mesh. It only occurs when something is placed on a planet. The trick I've used in the past to get around it is to make a flat plane mesh and place that just above the surface of the planet and use that as the ground. Looks great close up but at distances it's very ugly. The model surface does not conform to the curvature of the planet.

I discovered the cause of the jittering. It has nothing to do with any models, it has to do with virtual textures. I remove the VTs and put a standard texture on the planet and the jitter is gone.

Premise that now I understood the way in which you makes terrains, for what concern the terrain you want place on the VT tiles, note that with Bryce you can make a 256 grayscale image of the VT tiles and then to "extrude" your terrain. The more is white the more is high the terrain. Then, the terrain's texture can be the VT tile itself.