How do I pick different parts of a animated mesh?

pir · Post by **pir** » Sun May 03, 2009 7:32 pm

I want to be able to pick different parts on an animated mesh. What is the easiest way to do this?

I tried to use the bounding boxes of the scene::IBoneSceneNode in combination with ISceneManager::getSceneNodeFromScreenCoordinatesBB to pick arms legs etc.

It seems like the bounding boxes are not updated when the mesh is loaded. They all have values like: xmin=-1, ymin=-1, zmin=-1, xmax=1, ymax=1,zmax=1. It is only the bounding box for the actual mesh that is updated during loading.

Is there something I need to do to update the bounding boxes of the bones?

please tell me if my question is unclear.

BR
pir

Lonesome Ducky · Post by **Lonesome Ducky** » Sun May 03, 2009 8:18 pm

Well, if the model is split by materials, you can try checking all the mesh buffers seperately.

pir · Post by **pir** » Sun May 03, 2009 9:11 pm

No, it is only one big skinned mesh. For example, the dwarf model that is included in the Irrlicht examples.

I've found that it is possible to get the uppdated bounding boxes by using
irr::scene::IBoneSceneNodegetTransformedBoundingBox(). But I'm not sure that these are the bounding boxes that are used during the collision detection. Will check this tomorrow. But if anyone has any suggestions on how to solve my problem in a bettter way, please tell me.

Lonesome Ducky · Post by **Lonesome Ducky** » Sun May 03, 2009 11:09 pm

Oh, so are you trying to select the bones? If so, you can just cast a ray from the mouse and see if it hits the triangle selector of the object, if it does, find the closest bone to the collision point. Is that what you're looking for?

pir · Post by **pir** » Wed May 06, 2009 7:02 pm

Yes, thats what I want to do. I was thinking about doing it the way you described, was just hoping that there were some easier way to do it with bounding boxes. But since I can't make it work, I'll guess I should give it a try.

thanks

pir · Post by **pir** » Sun May 10, 2009 12:19 pm

Is there any functionality in Irrlicht that can help me finding the bone closest to my selected triangle?

Lonesome Ducky · Post by **Lonesome Ducky** » Sun May 10, 2009 3:37 pm

You can write your own. Just find the collision point and loop through all the bones, find the distance, and store the closest. If you need, I can right you some code.

pir · Post by **pir** » Sun May 10, 2009 3:49 pm

thanks, but I did it myself.

BR
pir

pir · Post by **pir** » Sun May 10, 2009 6:16 pm

Well, I thought that I had done it... but I have problems finding the correct bone. I think that it is caused by different transformation spaces... maybe. Thats only speculation. Here is my code for finding the closest bone:

Code: Select all

	scene::IAnimatedMesh* animMesh = m_mesh->getMesh( );
	assert( animMesh->getMeshType() == scene::EAMT_SKINNED);
	
	ISkinnedMesh* skinnedMesh = reinterpret_cast< ISkinnedMesh*>( animMesh);
	
	core::array< ISkinnedMesh::SJoint*>& allJoints = skinnedMesh->getAllJoints( );
	
	float           tmpDistance;
	float           minDistance;
	u32             minIndex;
	core::vector3df animatedPos;
	for( u32 j = 0; j < allJoints.size( ); j++)
	{
	    animatedPos = allJoints[ j]->Animatedposition;
	    tmpDistance = fabs( animatedPos.getDistanceFrom( tri.pointA));

	    if( ( tmpDistance < minDistance) || ( j == 0))
	    {
		minDistance = tmpDistance;
		minIndex    = j;
	    }
	    
	}// for j

The code is quick and dirty and only uses one point in the triangle.

I think that the triangle and the animated point from the current joint is in different transformation spaces, causing the false distances. But I'm not sure which transformation space to use, if this is the case.

pir · Post by **pir** » Sun May 10, 2009 6:47 pm

Ok, I found the problem. I shouldn't use SJoint::Animatedpos. I should use the transfomration matrix from the SJoint instead.