Rigidbody water interaction.

[Wimo135]

I have a mesh with a rigidbody and a global water object how can i make this mesh interact with the waves of the global water object

Edited January 6, 2022 by Wimo135

[fox]

Hi Wimo135,

This video may help you!

Thanks!

[Wimo135]

Thank you for your response. This is helpful but i already knew this, i would like to simulate the waves on the whole global water body/

[silent]

Wimo135

That would be impossible to achieve with the current hardware, unfortunately. You can use ObjectWaterGlobal API to get the wave height at the specific points and implement simplified ship buoyancy logic based on the information you get.

If you are using C++ you can check SDK Browser -> Demos -> CPP Samples -> Water Global with this approach implementation. For C# right now we don't have similar sample available out of the box, but it shouldn't be hard to port this code.

Thanks!

[Wimo135]

Thank you very much for your response, Im looking into this now.

[Wimo135]

Ive been trying to integrate this into my project recently but im running into a problem where my code just outputs a seemingly random number.
This is my code:

using System;

using System.Collections;

using System.Collections.Generic;

using Unigine;

using UnigineApp;

[Component(PropertyGuid = "c0bb98fbb56cba1ef20a5ae58789cf003de8765f")]

public class WaveDetector : Component

{

    public ObjectWaterGlobal water;

    public NodeDummy node;

    public float z;

    public Unigine.Object boat;

    private void Init()

    {

        // write here code to be called on component initialization

 

    }

   

    private void Update()

    {

        // write here code to be called before updating each render frame

        z = water.FetchHeight(node.Position);

        Log.Error(z);

        //boat.Position = new vec3(boat.Position.x, boat.Position.y, boat.Position.z + z);

    }

}

[silent]

What do you mean by random number? Can you show us full output?

FetchHeight returns distance between your point and wave height just below this point, so it can sometimes be negative (when your point is inside water volume).

 

[Wimo135]

I've resolved the issue, the issue was that i was using the local position of the dummy nodes instead of the world position, i have it working now.

[Wimo135]

However i still can't figure out how to rotate the object according to the points position.

[silent]

In C++ water samples there was an example that shows how to that rotation (in cpp_samples/source/water_buoy/BuoyComponent.cpp). You need at least 3 points that would represents ship.

[Wimo135]

Ive looked into that c++ file but i only see code for the location not the rotation of the boat.

[silent]

And what do you mean by rotation? Do you have any references?

[Wimo135]

I have been able to get the boat to move over the waves but i cant figure out how to make the boat rotate to the waves. for example if a wave is in front of the boat it should rotate up then go over the wave.

[cash-metall]

Hi
in BuoyComponent.cpp

	if (water)
	{
		auto node_transform = node->getWorldTransform(); // current transform matrix: (TRS: translate-rotation-scale)
		
      // point0, point1, point2 - position of control points
		Vec3 point0 = point_front_center->getWorldPosition();
		Vec3 point1 = point_back_left->getWorldPosition();
		Vec3 point2 = point_back_right->getWorldPosition();

		//create basis before transformation by 3 point
		Vec3 tmp_z = normalize(cross(normalize(point1 - point0), normalize(point2 - point0))); // up vector
		if (getAngle(vec3(tmp_z), vec3_up) > 90)
			tmp_z = -tmp_z;
		Vec3 tmp_y = normalize(point1 - point0); 
		Vec3 tmp_x = tmp_y;
		cross(tmp_x, tmp_y, tmp_z).normalize(); // right vector
		cross(tmp_y, tmp_z, tmp_x).normalize(); // forward
		Mat4 old_basis;
		old_basis.setTranslate(point0);
		old_basis.setColumn3(0, tmp_x);
		old_basis.setColumn3(1, tmp_y);
		old_basis.setColumn3(2, tmp_z);


		// find height for each controll point
		Scalar h0 = water->fetchHeight(Vec3(point0.x, point0.y, 0.0f));
		Scalar h1 = water->fetchHeight(Vec3(point1.x, point1.y, 0.0f));
		Scalar h2 = water->fetchHeight(Vec3(point2.x, point2.y, 0.0f));

		Scalar lerp_k = Game::getIFps() * mass_coef;
		
      	// smooth change height for each control point 
		point0.z = lerp(point0.z, h0, lerp_k);
		point1.z = lerp(point1.z, h1, lerp_k);
		point2.z = lerp(point2.z, h2, lerp_k);

		// calculate new basis the same way
		tmp_z = normalize(cross(normalize(point1 - point0), normalize(point2 - point0)));
		tmp_y = normalize(point1 - point0);
		cross(tmp_x, tmp_y, tmp_z).normalize();
		cross(tmp_y, tmp_z, tmp_x).normalize();
		Mat4 new_basis;
		new_basis.setTranslate(point0);
		new_basis.setColumn3(0, tmp_x);
		new_basis.setColumn3(1, tmp_y);
		new_basis.setColumn3(2, tmp_z);

		// calculate matrix for translation from old_basis to new_basis
		Mat4 translation_basis, new_transform;
		mul(translation_basis, new_basis, inverse(old_basis));

		// change node_transform by translation_basis
		mul(new_transform, translation_basis, node_transform);
		// apply node_transform
		node->setWorldTransform(new_transform);
	}
}

 

for better accurancy you need to take more than 3 points.

[Wimo135]

I understand this but i don't understand how to implement this in c#.

[karpych11]

Hello,

I ported buoyancy sample logic to C#. Hope this helps.

BuoyComponent.cs BuoySample.cs

[Wimo135]

Thanks very much this helped a lot!

Edited February 8, 2022 by Wimo135