TerrainGrid collision with model

Troubleshooting terramonkey
1

Hello :slight_smile:



I got a little problem trying to make the collision between the Ninja model and a TerrainGrid (generated from noise).



I tried this:



[java]CollisionShape terrainShape =

CollisionShapeFactory.createMeshShape((Node) terrain);

landscape = new RigidBodyControl(terrainShape, 0);

terrain.addControl(landscape);

PhysicsSpace().add(terrain);[/java]



I also put the debug mode by using this: bulletAppState.getPhysicsSpace().enableDebug(assetManager);



But when I start the application, the Ninja falls from the air to the ground passing through the terrain.



Don’t really understand why… By the way, I see a blue box around the Ninja but nothing around my terrain.



Thank you very much.

2

I guess you used a mesh collision shape for the ninja too, doesn’t work. Character, kinematic mode, kinematic rag doll are the keywords for you. The basic tutorials also contain a tutorial on the character.

3

Ok thank you, so even if the terrain has a mesh collision shape, nothing will appear by debugging ?



I used this for the Ninja:



[java]

private CharacterControl player;

private Node model;

CapsuleCollisionShape capsuleShape = new CapsuleCollisionShape(1.5f, 6f, 1);

player = new CharacterControl(capsuleShape, 0.05f);

player.setJumpSpeed(20);

player.setFallSpeed(30);

player.setGravity(30);

model = (Node) assetManager().loadModel("Models/Ninja.mesh.xml");

model.addControl(player);

model.setLocalScale(0.05f, 0.05f, 0.05f);

player.setPhysicsLocation(new Vector3f(0f, 180f, -50f));

bulletAppState.getPhysicsSpace().add(player);

rootNode().attachChild(model);[/java]

4
@drweedy said:

Don't really understand why... By the way, I see a blue box around the Ninja but nothing around my terrain.


Yes that seems to be a quirk of jBullet that the debug mesh isn't shown for the terrain.

I guess it is possible that you might "tunnel" through the terrain if the ninja falls very far (i.e. moving very fast), you have a pretty high gravity which might cause this perhaps. Worth a shot at least.
5

Tried putting the Ninja really close of the terrain and it doesn’t change anything.



Is the collisionshape code for my terrain good or not?



Als, I use a TerrainGrid, could it be for something?

Thx.



EDIT:



Maybe should I use the “terrain.getGridTileLoader().getTerrainQuadAt(new Vector3f(0f, 150f, 0f)));” when I use createMeshShape.

But it doesn’t do anything,.

6

I found something :



I tried this : [java]RigidBodyControl terrainShape = new RigidBodyControl(CollisionShapeFactory.createMeshShape(terrain), 0);

terrain.addControl(terrainShape);[/java]



terrain is a TerrainGrid object.



And the Ninja falls through the floor but stop at y = 0;



And “terrain.getHeight()” return 0.0 for every point of the terrain.



So it seems to be linked.

7
@jmaasing said:
Yes that seems to be a quirk of jBullet that the debug mesh isn't shown for the terrain.

Bullet and jme use a heightfield for the collision object, not an actual collision mesh (better performance). So it can't really render a shape to represent it as it is just a grid of height points, unless it did create a strip mesh but that wouldn't guarantee to exactly represent the actual terrain mesh and could be slightly misleading.
8
@Sploreg said:
Bullet and jme use a heightfield for the collision object, not an actual collision mesh (better performance). So it can't really render a shape to represent it as it is just a grid of height points, unless it did create a strip mesh but that wouldn't guarantee to exactly represent the actual terrain mesh and could be slightly misleading.

Yes, but native-bullet actually draw a blue strip-mesh in debug mode, although as you say it is not accurate it at least shows there is something there :)
9

So, no one knows how to make this TerrainGrid solid ?

10

Theres even examples doing it with physics. E.g. TerrainGridTileLoaderTest.

11

Implement TerrainGridListener in the class that does the physics stuff, and overwrite the methods to apply a collision shape for each added terrain when it’s loaded. Then use it to remove the shape when the tile is unloaded. You can’t generate a terrain grid shape, since the terrain grid isn’t static. You have to modify it every time a tile is loaded/unloaded.



Also I’m pretty sure you have to add and remove the collision shape from the physics space manually, I don’t think creating the control and adding it to the terrain is enough.



EDIT: beat…

12

Thank you very much ! I’ll take a look at the TerrainGridTileLoaderTest class later. But I tired it and it works fine :slight_smile:



With this class and androlo’s explanations it would be good :slight_smile:



Thanks a lot!



EDIT: Works fine ! :slight_smile: