fix: npe in depth shader diffuseTexture

[dar-dev]

Line: https://github.com/libgdx/libgdx/blob/7fb396541a8c2777c92a5062aaa49afcab0bec1f/gdx/src/com/badlogic/gdx/graphics/g3d/shaders/DefaultShader.java#L237C32-L237C50

This is throwing an npe because the DepthShader canRender() is recycling the shader without the diffuse texture attribute.

Step to replicate:

• open: "gdx-gltf-demo-desktop-2.1.0.jar" from gdx-gltf repo (https://github.com/mgsx-dev/gdx-gltf)
• load this glTF model: https://sketchfab.com/3d-models/2021-lamborghini-countach-lpi-800-4-d76b94884432422b966d1a7f8815afb5
• enable shadow pass from gltf scene manager
• npe

[mgsx-dev]

It fixes the issue you have but it introduces a regression : let say you have 2 models without blending, one with a diffuse texture and another one without diffuse texture, 2 shaders will be generated instead of one. And will then produce some unnecessary shader switches when rendering.

[dar-dev]

It fixes the issue you have but it introduces a regression : let say you have 2 models without blending, one with a diffuse texture and another one without diffuse texture, 2 shaders will be generated instead of one. And will then produce some unnecessary shader switches when rendering.

If we use the same shader an npe is thrown, so.. it never worked (at least in our tests).
How can we avoid this shader switch ? Do we need to introduce an npe check in diffuseTexture local setter ?

--

[Tom-Ski]

What is the minimal pure libgdx repro steps here? Having a demo with gltf dependency is not very suitable for the tracker.
Is it two renderables with diffuse texture? One with diffuse texture, one not? Whats the minimum combination required for this to die?

[dar-dev]

To replicate in libgdx you need to render 2 different renderables using depthshader: one with diffuse texture and the other without.

--

[Tom-Ski]

Using a slightly modified version of the ShadowMappingTest does not reproduce this.

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package com.badlogic.gdx.tests.g3d;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.PerspectiveCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.VertexAttributes.Usage;
import com.badlogic.gdx.graphics.g3d.Environment;
import com.badlogic.gdx.graphics.g3d.Material;
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.BlendingAttribute;
import com.badlogic.gdx.graphics.g3d.attributes.ColorAttribute;
import com.badlogic.gdx.graphics.g3d.attributes.TextureAttribute;
import com.badlogic.gdx.graphics.g3d.environment.DirectionalShadowLight;
import com.badlogic.gdx.graphics.g3d.utils.CameraInputController;
import com.badlogic.gdx.graphics.g3d.utils.DepthShaderProvider;
import com.badlogic.gdx.graphics.g3d.utils.MeshPartBuilder;
import com.badlogic.gdx.graphics.g3d.utils.ModelBuilder;
import com.badlogic.gdx.math.Vector3;
import com.badlogic.gdx.tests.utils.GdxTest;

public class ShadowMappingTest extends GdxTest {
    PerspectiveCamera cam;
    CameraInputController camController;
    ModelBatch modelBatch;
    Model model;
    ModelInstance instance;
    ModelInstance instance2;
    Environment environment;
    DirectionalShadowLight shadowLight;
    ModelBatch shadowBatch;
    private Model model2;

    @Override
    public void create () {
        modelBatch = new ModelBatch();
        environment = new Environment();
        environment.set(new ColorAttribute(ColorAttribute.AmbientLight, .4f, .4f, .4f, 1f));
        environment
                .add((shadowLight = new DirectionalShadowLight(1024, 1024, 30f, 30f, 1f, 100f)).set(0.8f, 0.8f, 0.8f, -1f, -.8f, -.2f));
        environment.shadowMap = shadowLight;

        cam = new PerspectiveCamera(67, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
        cam.position.set(0f, 7f, 10f);
        cam.lookAt(0, 0, 0);
        cam.near = 1f;
        cam.far = 50f;
        cam.update();

        ModelBuilder modelBuilder = new ModelBuilder();

        modelBuilder.begin();
        MeshPartBuilder mpb = modelBuilder.part("parts", GL20.GL_TRIANGLES, Usage.Position | Usage.Normal | Usage.ColorUnpacked | Usage.TextureCoordinates,
                new Material(TextureAttribute.createDiffuse(new Texture(Gdx.files.internal("data/badlogic.jpg")))));
        mpb.setColor(1f, 1f, 1f, 1f);
        mpb.sphere(2f, 2f, 2f, 10, 10);
        model = modelBuilder.end();
        instance = new ModelInstance(model);

        modelBuilder.begin();
        mpb = modelBuilder.part("parts2", GL20.GL_TRIANGLES, Usage.Position | Usage.Normal | Usage.ColorUnpacked,
            new Material());
        mpb.setColor(1f, 1f, 1f, 1f);
        mpb.sphere(4f, 2f, 2f, 10, 10);
        model2 = modelBuilder.end();
        instance2 = new ModelInstance(model2);


        shadowBatch = new ModelBatch(new DepthShaderProvider());

        Gdx.input.setInputProcessor(camController = new CameraInputController(cam));
    }

    @Override
    public void render () {
        camController.update();

        Gdx.gl.glViewport(0, 0, Gdx.graphics.getBackBufferWidth(), Gdx.graphics.getBackBufferHeight());
        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);

        instance2.transform.setToTranslation(4, 0, 0);

        shadowLight.begin(Vector3.Zero, cam.direction);
        shadowBatch.begin(shadowLight.getCamera());
        shadowBatch.render(instance);
        shadowBatch.render(instance2);
        shadowBatch.end();
        shadowLight.end();

        modelBatch.begin(cam);
        modelBatch.render(instance, environment);
        modelBatch.render(instance2, environment);
        modelBatch.end();
    }

    @Override
    public void dispose () {
        modelBatch.dispose();
        model.dispose();
        model2.dispose();
    }

    public boolean needsGL20 () {
        return true;
    }

    public void resume () {
    }

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

    public void pause () {
    }
}