Render a sphere when the user clicks on the screen with libgdx

Question

I’m really new to Libgdx, and decided to try out some codes to familiarise myself with it. I’m trying to write a program such that a sphere is rendered at the position of the user’s click.

Here’s my code:

package com.mygdx.game;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.PerspectiveCamera;
import com.badlogic.gdx.graphics.VertexAttributes.Usage;
import com.badlogic.gdx.graphics.g3d.Environment;
import com.badlogic.gdx.graphics.g3d.Model;
import com.badlogic.gdx.graphics.g3d.ModelBatch;
import com.badlogic.gdx.graphics.g3d.ModelInstance;
import com.badlogic.gdx.graphics.g3d.attributes.ColorAttribute;
import com.badlogic.gdx.graphics.g3d.environment.DirectionalLight;
import com.badlogic.gdx.graphics.g3d.Material;
import com.badlogic.gdx.graphics.g3d.utils.CameraInputController;
import com.badlogic.gdx.graphics.g3d.utils.ModelBuilder;
import com.badlogic.gdx.InputAdapter;
import com.badlogic.gdx.graphics.FPSLogger;

public class Render implements ApplicationListener {
    public Environment environment;
    public PerspectiveCamera cam;
    public CameraInputController camController;
    public ModelBatch modelBatch;
    private FPSLogger fps;

    public Model model;

    @Override
    public void create() {
        Gdx.graphics.setContinuousRendering(false);

        environment = new Environment();
        environment.set(new ColorAttribute(ColorAttribute.Specular, 0.4f, 0.4f, 0.4f, 0.6f));
        environment.add(new DirectionalLight().set(0.8f, 0.8f, 0.8f, 0f, 0f, -1f));

        modelBatch = new ModelBatch();

        cam = new PerspectiveCamera(67, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
        cam.position.set(0f, 0f, 10f);
        cam.lookAt(0,0,0);
        cam.near = 1f;
        cam.far = 300f;
        cam.update();

        ModelBuilder modelBuilder = new ModelBuilder();
        model = modelBuilder.createSphere(1f, 1f, 1f, 30, 30,
                new Material(), Usage.Position | Usage.Normal)
        camController = new CameraInputController(cam);
        Gdx.input.setInputProcessor(camController);
        fps = new FPSLogger();
    }

    @Override
    public void render() {




        if (Gdx.input.justTouched()){
            ModelInstance Instance = new ModelInstance (model);
             Instance.transform.setToTranslation(Gdx.input.getX(),Gdx.input.getY(), 0);
            DataBase.array.add(Instance);
            Gdx.graphics.requestRendering();
        }
        camController.update();

        Gdx.gl.glViewport(0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);

        modelBatch.begin(cam);
        for (ModelInstance instance: DataBase.array) {
            modelBatch.render(instance, environment);
        }
        modelBatch.end();




        //fps.log();
    }


    @Override
    public void dispose() {
        modelBatch.dispose();
        model.dispose();
    }




    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }
}

The DataBase.array is simply an ArrayList.

What am I doing wrong? Any help would be really appreciated; thanks!

Answer 1

I see few mistakes in your code :

environment.set(new ColorAttribute(ColorAttribute.Specular, 0.4f, 0.4f, 0.4f, 0.6f));

It has no effect since specular should only used with materials. Maybe you wanted ambiant light. Then replace it by ColorAttribute.AmbientLight.

The main problem in your case is coordinates conversion from screen space to world space. What you can do is :

// get screen space Z from world space zero
float z = cam.project(new Vector3(0,0,0)).z;
// get world space position from screen space pointer
Vector3 v = cam.unproject(new Vector3(Gdx.input.getX(),Gdx.input.getY(), z));
// set your model position in world space
Instance.transform.setToTranslation(v.x, v.y, v.z);