Custom Animation with Bones

Troubleshooting General Help
1

I founded tutorial how to create custom animation with bones in Jme Tests. I not undarstand some code lines.

package jme3test.model.anim;

import com.jme3.animation.Bone;

import com.jme3.animation.Skeleton;

import com.jme3.animation.SkeletonControl;

import com.jme3.app.SimpleApplication;

import com.jme3.light.AmbientLight;

import com.jme3.light.DirectionalLight;

import com.jme3.math.Quaternion;

import com.jme3.math.Vector3f;

import com.jme3.scene.Geometry;

import com.jme3.scene.Mesh;

import com.jme3.scene.Node;

import com.jme3.scene.VertexBuffer;

import com.jme3.scene.VertexBuffer.Format;

import com.jme3.scene.VertexBuffer.Type;

import com.jme3.scene.VertexBuffer.Usage;

import com.jme3.scene.shape.Box;

import java.nio.ByteBuffer;

import java.nio.FloatBuffer;

public class TestCustomAnim extends SimpleApplication {

private Bone bone;

private Skeleton skeleton;

private Quaternion rotation = new Quaternion();

public static void main(String[] args) {

TestCustomAnim app = new TestCustomAnim();

app.start();

}

@Override

public void simpleInitApp() {

AmbientLight al = new AmbientLight();

rootNode.addLight(al);

DirectionalLight dl = new DirectionalLight();

dl.setDirection(Vector3f.UNIT_XYZ.negate());

rootNode.addLight(dl);

Box box = new Box(1, 1, 1);

// Setup bone weight buffer

FloatBuffer weights = FloatBuffer.allocate( box.getVertexCount() * 4 ); Why box verts are multiply from 4?

VertexBuffer weightsBuf = new VertexBuffer(Type.BoneWeight);

weightsBuf.setupData(Usage.CpuOnly, 4, Format.Float, weights);

box.setBuffer(weightsBuf);

// Setup bone index buffer

ByteBuffer indices = ByteBuffer.allocate( box.getVertexCount() * 4 );Why box verts are multiply from 4?

VertexBuffer indicesBuf = new VertexBuffer(Type.BoneIndex);

indicesBuf.setupData(Usage.CpuOnly, 4, Format.UnsignedByte, indices);

box.setBuffer(indicesBuf);

// Create bind pose buffers

box.generateBindPose(true);

// Create skeleton

bone = new Bone(“root”);

bone.setBindTransforms(Vector3f.ZERO, Quaternion.IDENTITY, Vector3f.UNIT_XYZ);

bone.setUserControl(true);

skeleton = new Skeleton(new Bone[]{ bone });

// Assign all verticies to bone 0 with weight 1

for (int i = 0; i < box.getVertexCount() * 4; i += 4){Why box verts are multiply from 4?

// assign vertex to bone index 0

indices.array()[i+0] = 0;

indices.array()[i+1] = 0;

indices.array()[i+2] = 0;

indices.array()[i+3] = 0;

// set weight to 1 only for first entry

weights.array()[i+0] = 1;

weights.array()[i+1] = 0;

weights.array()[i+2] = 0;

weights.array()[i+3] = 0;

}

// Maximum number of weights per bone is 1

box.setMaxNumWeights(1);

// Create model

Geometry geom = new Geometry(“box”, box);

geom.setMaterial(assetManager.loadMaterial(“Textures/Terrain/BrickWall/BrickWall.j3m”));

Node model = new Node(“model”);

model.attachChild(geom);

// Create skeleton control

SkeletonControl skeletonControl = new SkeletonControl(new Mesh[]{ box }, skeleton);

model.addControl(skeletonControl);

rootNode.attachChild(model);

}

@Override

public void simpleUpdate(float tpf){

// Rotate around X axis

Quaternion rotate = new Quaternion();

rotate.fromAngleAxis(tpf, Vector3f.UNIT_X);

// Combine rotation with previous

rotation.multLocal(rotate);

// Set new rotation into bone

bone.setUserTransforms(Vector3f.ZERO, rotation, Vector3f.UNIT_XYZ);

// After changing skeleton transforms, must update world data

skeleton.updateWorldVectors();

}

}

2

A vertex can be influenced by 4 bones

for each vertex, the bones’ index and weight are stored in a float buffer.

so if you have 10 vertices, you have 40 indices and weights.