How to render a running Animate sprite on a RenderTexture？

[hasikill]

• After calling SnapshotToTexture, the result is a white image without the image of the current animation frame.

class GameEntity : public ax::Sprite
{
    ...
    std::vector<ax::RefPtr<Animation>> animations;

    ...
    auto SnapshotToTexture() -> ax::RefPtr<ax::Texture2D>
    {
        ax::Vec2 size(0, 0);
        for (auto& e : animations)
        {
            auto frameSize = e->getFrameMaxSize();
            size.width     = std::max(size.width, frameSize.width);
            size.height    = std::max(size.height, frameSize.height);
        }

        if (size.width <= 0 || size.height <= 0)
        {
            size.set(1, 1);
        }

        ax::RefPtr<ax::RenderTexture> rt = ax::RenderTexture::create(size.width, size.height);
        if (!rt)
        {
            return nullptr;
        }

        rt->beginWithClear(1, 1, 1, 1);
        for (auto& e : animations)
        {
            e->visit();
        }
        rt->end();

        return rt->getSprite()->getTexture();
    }

    void update(float delta) override {
        Sprite::update(delta);
        for (auto& e : animations)
        {
            e->update(delta);
        }
    }
    // ...
};

[rh101]

Please show the usage of SnapshotToTexture. For example, where is it called from?

Even better would be if you upload a minimal working project to show how the code is being used.

One thing that I don't understand is how the code you posted would actually compile. The Animation class has no visit() method, yet your code shows this:

rt->beginWithClear(1, 1, 1, 1);
for (auto& e : animations)
{
    e->visit();
}
rt->end();

So, it doesn't make much sense. Does the code you posted actually compile? Did you add a visit() method to the Animation class?

Refer to the {axmol_dir}/tests/cpp-tests project for examples of how animations are played. All the code is in there to show you how it works.

[hasikill]

Comment on line 299 of the code this->addChild(d_entity);
If I don't add g-entity to MainScene, then there won't be anything displayed on the IMGUI window. Why is this.

[rh101]

If I don't add g-entity to MainScene, then there won't be anything displayed on the IMGUI window. Why is this.

Please explain exactly what is you're trying to achieve.

If you don't want the GameEntity to be displayed to the screen, then you need to handle initializing it manually, which means calling onEnter(), onExit(), update() and whatever other methods would usually be called when it's part of the scene graph. That requires an understanding of how the node system worrks, and if you want to do that, then you're going to have to dive into the engine code to understand it better.

[hasikill]

Yes, I want to draw animated sprites on GPU textures. I have used other libraries such as raylib, and implementing this feature is very simple. The code looks like this:

Texture2D texture1 = LoadTexture("1.png");
Texture2D texture2 = LoadTexture("2.png");
RenderTexture2D targetTexture = LoadRenderTexture(300, 300);

BeginTextureMode(targetTexture);
DrawTexture(texture1, 0, 0, WHITE);
DrawTexture(texture2, 0, 0, WHITE);
EndTextureMode();  

[rh101]

How another library handles it has nothing to do with Axmol, so it's not something you can easily port across.

Now, if you want to get this working, then once again, you need to gain a better understanding of how the node system works in Axmol.

For this specific case, and assuming you don't want to render the g_entity in the scene, then this is what you do:

Create the entity and add the animations to it in MainScene::init():

std::vector<RefPtr<game::Animation>> animations;
animations.push_back(game::Animation::Create("res/base.png", 10, 96, 64));
animations.push_back(game::Animation::Create("res/bowlhair.png", 10, 96, 64));
animations.push_back(game::Animation::Create("res/tools.png", 10, 96, 64));

g_entity = game::GameEntity::CreateWithAnimations(animations);

Do not add g_entity to the scene via addChild.

In MainScene::onEnter(), make sure you call the onEnter of the sprite that are not adding to the scene:

void MainScene::onEnter()
{
    Scene::onEnter();

    if (g_entity)
    {
        g_entity->onEnter();
    }
    extension::ImGuiPresenter::getInstance()->enableDPIScale();
    extension::ImGuiPresenter::getInstance()->addRenderLoop("#test", AX_CALLBACK_0(MainScene::onDrawImGui, this), this);
}

Override onExit as well, since it's a good enough location to call g_entity->onExit():

void MainScene::onExit()
{
    if (g_entity)
    {
        g_entity->onExit();
    }
    Scene::onExit();
}

Note that if you call Node::onEnter(), but forget to call Node::onExit(), then you will get a crash, so make sure you always match one with the other.

Also, make sure the methods you override have the override specifier on them, since you forgot that in your code for onEnter:

void onEnter() override;
void onExit() override;

Now, to render the animated sprites, position them correctly:

rt->beginWithClear(1, 1, 1, 1);
for (auto& e : animations)
{
    e->setPosition(Vec2(0.f, 0.f));
    e->setAnchorPoint(Vec2::ANCHOR_BOTTOM_LEFT);
    e->visit();
}
rt->end();

Then you get this output:

[hasikill]

Thanks, exactly what I was looking for! One more thing: for a frame-by-frame animation, where should I put the code for hitboxes and hit detection? It probably needs to trigger on a specific frame.

[rh101]

I'm not sure about hit boxes and hit detection, but perhaps the cpp-tests project may have an example, or at least point you in the right direction. Build that project and see how things work. It's in {axmol}/tests/cpp-tests.

You can also see the cpp-tests project running in the browser here: https://axmol.netlify.app/wasm/cpp-tests/cpp-tests

[hasikill]

OK