Renderer/src/main/java/electrosphere/collision/CollisionBodyCreation.java

package electrosphere.collision;

import java.nio.IntBuffer;

import org.joml.Vector3d;
import org.lwjgl.PointerBuffer;
import org.lwjgl.assimp.AIFace;
import org.lwjgl.assimp.AIMesh;
import org.lwjgl.assimp.AIScene;
import org.lwjgl.assimp.AIVector3D;
import org.ode4j.ode.DBody;
import org.ode4j.ode.DBox;
import org.ode4j.ode.DCylinder;
import org.ode4j.ode.DSphere;
import org.ode4j.ode.DTriMesh;

import electrosphere.entity.types.terrain.TerrainChunkData;

/**
 * Utilities for creating types of rigid bodies
 */
public class CollisionBodyCreation {


    
    //The width of a plane rigid body
    //It's really a box under the hood
    static final double PLANE_WIDTH = 0.3;

    /**
     * Creates a plane DBody. Dimensions x and z control the length and width of the plane;
     * @param dimensions The dimensions of the plane
     * @return The DBody
     */
    public static DBody createPlaneBody(CollisionEngine collisionEngine, Vector3d dimensions){
        DBox geom = collisionEngine.createCubeGeom(new Vector3d(dimensions.x,PLANE_WIDTH,dimensions.z));
        return collisionEngine.createDBody(geom);
    }

    /**
     * Creates a cube DBody. Dimensions controlled by the dimensions vector.
     * @param collisionEngine The collision engine to create the body inside of
     * @param dimensions The dimensions of the cube
     * @return The DBody
     */
    public static DBody createCubeBody(CollisionEngine collisionEngine, Vector3d dimensions){
        DBox geom = collisionEngine.createCubeGeom(new Vector3d(dimensions));
        return collisionEngine.createDBody(geom);
    }

    /**
     * Creates a cylinder DBody. Dimensions controlled by the dimensions vector.
     * @param collisionEngine The collision engine to create the body inside of
     * @param dimensions The dimensions of the cube
     * @return The DBody
     */
    public static DBody createCylinderBody(CollisionEngine collisionEngine, double radius, double length){
        DCylinder geom = collisionEngine.createCylinderGeom(radius,length);
        return collisionEngine.createDBody(geom);
    }

    /**
     * Creates a sphere body in the collision engine
     * @param collisionEngine The collision engine
     * @param radius The radius of the sphere
     * @return The DBody
     */
    public static DBody createSphereBody(CollisionEngine collisionEngine, double radius){
        DSphere geom = collisionEngine.createSphereGeom(radius);
        return collisionEngine.createDBody(geom);
    }

    
    /**
     * Creates an ode DBody from a terrain chunk data object
     * @param data The terrain data
     * @return The DBody
     */
    public static DBody generateBodyFromTerrainData(CollisionEngine collisionEngine, TerrainChunkData data){
        DBody body = null;
        
        //create data
        int numberTriangles = data.getFaceElements().size() / 3;
        int numberVertices = data.getVertices().size() / 3;
        
        float[] vertices = new float[numberVertices * 3];
        int vertexInserterPos = 0;
        int[] indices = new int[numberTriangles * 3];
        int indexInserterPos = 0;
        
        for(float vertexValue : data.getVertices()){
            vertices[vertexInserterPos] = vertexValue;
            vertexInserterPos++;
        }

        for(int element : data.getFaceElements()){
            indices[indexInserterPos] = element;
            indexInserterPos++;
        }
        
        //create trimesh
        if(vertices.length > 0){
            DTriMesh triMesh = collisionEngine.createTrimeshGeom(vertices,indices);
            body = collisionEngine.createDBody(triMesh);
        }

        return body;
    }

    /**
     * Generates a body from an AIScene
     * @param scene The AIScene to generate a rigid body off of
     * @return A rigid body based on the AIScene
     */
    public static DBody generateRigidBodyFromAIScene(CollisionEngine collisionEngine, AIScene scene){

        DBody body = collisionEngine.createDBody(null);

        PointerBuffer meshesBuffer = scene.mMeshes();
        while(meshesBuffer.hasRemaining()){
            float[] verts;
            int numVertices;
            int[] indices;
            int numTriangles;

            AIMesh aiMesh = AIMesh.create(meshesBuffer.get());
            //allocate array for vertices
            numVertices = aiMesh.mNumVertices();
            verts = new float[numVertices * 3];
            //read vertices
            AIVector3D.Buffer vertexBuffer = aiMesh.mVertices();
            int vertPos = 0;
            while(vertexBuffer.hasRemaining()){
                AIVector3D vector = vertexBuffer.get();
                verts[vertPos+0] = vector.x();
                verts[vertPos+1] = vector.y();
                verts[vertPos+2] = vector.z();
                vertPos = vertPos + 3;
            }
            numTriangles = aiMesh.mNumFaces();
            indices = new int[numTriangles * 3];
            int indicesPos = 0;
            //read faces
            AIFace.Buffer faceBuffer = aiMesh.mFaces();
            while(faceBuffer.hasRemaining()){
                AIFace currentFace = faceBuffer.get();
                IntBuffer indexBuffer = currentFace.mIndices();
                while(indexBuffer.hasRemaining()){
                    int index = indexBuffer.get();
                    indices[indicesPos] = index;
                    indicesPos++;
                }
            }
            DTriMesh meshGeom = collisionEngine.createTrimeshGeom(verts, indices);
            meshGeom.setBody(body);
        }
        
        return body;
    }
    
}