Ok. I think I might've found the issue, though I'm not 100% about it.
So it looks like the issue shows itself when you have a compound object colliding the terrain, instead of a simple single convex shape colliding with it. I've also found what seems to be the fix, but like I said, I'm not 100%.
Here's how I changed the TerrainDemo to get it going:
Code: Select all
public TerrainDemo(DemosGame game)
: base(game)
{
//x and y, in terms of heightmaps, refer to their local x and y coordinates. In world space, they correspond to x and z.
//Setup the heights of the terrain.
//[The size here is limited by the Reach profile the demos use- the drawer draws the terrain as a big block and runs into primitive drawing limits.
//The physics can support far larger terrains!]
int xLength = 180;
int zLength = 180;
float xSpacing = 8f;
float zSpacing = 8f;
var heights = new float[xLength, zLength];
for (int i = 0; i < xLength; i++)
{
for (int j = 0; j < zLength; j++)
{
float x = i - xLength / 2;
float z = j - zLength / 2;
//heights[i,j] = (float)(x * y / 1000f);
heights[i, j] = (float)(10 * (Math.Sin(x / 8) + Math.Sin(z / 8)));
//heights[i,j] = 3 * (float)Math.Sin(x * y / 100f);
//heights[i,j] = (x * x * x * y - y * y * y * x) / 1000f;
}
}
//Create the terrain.
var terrain = new Terrain(heights, new AffineTransform(
new Vector3(xSpacing, 1, zSpacing),
Quaternion.Identity,
new Vector3(-xLength * xSpacing / 2, 0, -zLength * zSpacing / 2)));
terrain.Material.KineticFriction = 0f;
terrain.Material.StaticFriction = 0f;
//terrain.Thickness = 5; //Uncomment this and shoot some things at the bottom of the terrain! They'll be sucked up through the ground.
Space.Add(terrain);
//for (int i = 0; i < 3; i++)
//{
// for (int j = 0; j < 3; j++)
// {
// for (int k = 0; k < 5; k++)
// {
// Space.Add(new Box(
// new Vector3(0 + i * 4, 100 - j * 10, 0 + k * 4),
// 2 + i * j * k,
// 2 + i * j * k,
// 2 + i * j * k,
// 4 + 20 * i * j * k));
// }
// }
//}
//Build the first body
var bodies = new List<CompoundShapeEntry>()
{
new CompoundShapeEntry(new BoxShape(1,1,1), new Vector3(0, 50, 0), 1),
new CompoundShapeEntry(new BoxShape(1,1,1), new Vector3(1, 50.5f, 0), 1),
};
var cb2 = new CompoundBody(bodies, 4);
Space.Add(cb2);
game.ModelDrawer.Add(terrain);
game.Camera.Position = new Vector3(0, 30, 20);
}
Basically, I removed the single boxes, and added a compound object to the simulation. I also tried to kill the friction and in theory the boxes should slide around but they don't (or didn't when I tried it), whereas the single boxes do slide around.
As far as tracking down what I think the bug is, it looks like it might be this function in CompoundTerrainPairHandler.cs:
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protected override void UpdateContainedPairs()
{
//Could go other way; get triangles in mesh that overlap the compound.
//Could be faster sometimes depending on the way it's set up.
var overlappedElements = Resources.GetCompoundChildList();
compoundInfo.hierarchy.Tree.GetOverlaps(terrain.boundingBox, overlappedElements);
for (int i = 0; i < overlappedElements.count; i++)
{
TryToAdd(overlappedElements.Elements[i].CollisionInformation, terrain, overlappedElements.Elements[i].Material);
}
Resources.GiveBack(overlappedElements);
}
The TryToAdd() function doesn't send in the terrain material. It only sends in the other collidable's material. If I change that line to be:
Code: Select all
TryToAdd(overlappedElements.Elements[i].CollisionInformation, terrain, overlappedElements.Elements[i].Material, terrain.Material);
Then it looks like it works as intended.
Let me know what you make of this.
Cheers
. If i hard code the values I want in that function, then I get the expected visual results in the app. I've also checked to make sure that calls to UpdateMaterialProperties() comes back with the expected values, so the issue seems to be somewhere when it's going from the blended material values to the point they're fed into the contactManifordConstraint, and I didn't dig any deeper at the moment particularly the intertwined calls between contact manifolds, and pair handlers seem to get get a bit hairy to track without knowing the exact architecture and naming convention in BEPU.
