Problems with Transitions

[IcemarkUK]

I'm having a few issues with transitions.

Firstly, TransitionCrossFade is not fading between two scenes. It seems to fade between a blank scene and the one I'm leaving. The scene I'm entering appears at the end of the duration. If I s

Here is my trigger of the transition.

        Director* director = Director::getInstance();
        director->pushScene(TransitionCrossFade::create(defaultDuration, incomming) );

fadein.mov

One of my Scenes has a ScrollView with a TMXTiledMap inside it. If I CrossFade to that scene it crashes in the following code. Basically getVisitingCamera is null.

If I change to another transition, it works fine.

void FastTMXLayer::draw(Renderer* renderer, const Mat4& transform, uint32_t flags)
{
    updateTotalQuads();

    auto cam = Camera::getVisitingCamera();
    if (flags != 0 || _dirty || _quadsDirty || !_cameraPositionDirty.fuzzyEquals(cam->getPosition(), _tileSet->_tileSize.x) ||
        _cameraZoomDirty != cam->getZoom())
    {
        _cameraPositionDirty = cam->getPosition();

And finally - the slide transitions are tearing really badly. Couldn't capture in video as the seem fine in the recording!

[rh101]

Firstly, TransitionCrossFade is not fading between two scenes. It seems to fade between a blank scene and the one I'm leaving. The scene I'm entering appears at the end of the duration.

It's definitely different from the way it worked in cocos2d-x, and it seems that no one noticed. The cpp-tests project also shows the issue, where it fades to a black screen before popping up the new scene, which is not correct.

[rh101]

@IcemarkUK Fixed in #1664

[IcemarkUK]

Perfect, thank you that works.

[rh101]

One of my Scenes has a ScrollView with a TMXTiledMap inside it. If I CrossFade to that scene it crashes in the following code. Basically getVisitingCamera is null.

And finally - the slide transitions are tearing really badly. Couldn't capture in video as the seem fine in the recording!

Any chance you could make a simple test project, or even just post the code, which reproduces each of these issues?

[IcemarkUK]

@rh101
Changing the following

axmol/core/2d/FastTMXLayer.cpp

Lines 131 to 138 in dad167b

	void FastTMXLayer::draw(Renderer* renderer, const Mat4& transform, uint32_t flags)
	{
	updateTotalQuads();
	auto cam = Camera::getVisitingCamera();
	if (flags != 0 || _dirty || _quadsDirty || !_cameraPositionDirty.fuzzyEquals(cam->getPosition(), _tileSet->_tileSize.x) ||
	_cameraZoomDirty != cam->getZoom())
	{

To add a null check at L136, fixes the issue. The transition isn't working properly, but at least it doesn't crash.

if (cam == nullptr) return;

[IcemarkUK]

This is essentially because setNextScene is called before the cameras are set up in renderScene. And this happens with all transitions.

TransitionCrossFade seems to be the only transition that calls _inScene->visit() inside onEnter which triggers a Draw - which it does in order to create the render textures. The OnEnter is triggered inside setNextScene.

[rh101]

Interesting find, and I wonder when it changed between Cocos2d-x and Axmol, and the reason why.

Please submit a PR with the modification that fixes the issue.

[rh101]

The issue seems to have been introduced in this PR, which was to fix a different issue: #1134

Adding that null check is required to fix the issue you're experiencing, and similar checks are used in draw code of other nodes that access the camera at that point.

Does the fact that it does not draw anything affect the transition, in terms of showing the correct output from the tiled map?

[IcemarkUK]

Adding the null check stops the render texture from capturing the initial scene, so the transition doesn't cross fade correctly. So it's not a fix.
I don't think that #1134 fix broke this, as the code previously still accessed the camera to get the position. Quickly swapping out the function for the Cocos2d-x one still crashes. I suspect it has something to do with the transitions triggering setNextScene and maybe that didn't happen before. I'll follow that process when I'm back home in a couple of days and can run the Cocos build.

[rh101]

@IcemarkUK The entire issue with this is that the camera isn't being set prior to processing all internal nodes. I'm not sure why it would have worked in Cocos2d-x. since none of the transition code seems to have changed between cocos2d-x and axmol, including when it switches to the next scene.

There is a potential fix that, to my knowledge, will not affect anything but this specific issue. A few observations related to it:

• Scene:visit() is unused outside of attempting to render a scene to a render texture.
• Node::visit() is both virtual and final, which is strange, since it should be one or the other, and I don't know the reason why it has the final specifier. It needs to be virtual because it is overloaded.

My proposal here is that the final specifier is removed from Node::visit(), yet keep it as a virtual method. In this case, it actually helps fix this issue, since we can override it in Scene::visit(), and simply implement the following:

void Scene::visit()
{
    const auto eyeTransform = Mat4::IDENTITY;

    for (const auto& camera : getCameras())
    {
        if (!camera->isVisible())
            continue;

        Camera::_visitingCamera = camera;

        camera->setAdditionalTransform(eyeTransform.getInversed());
        _director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION);
        _director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION,
                              Camera::_visitingCamera->getViewProjectionMatrix());

        camera->apply();
        // clear background with max depth
        camera->clearBackground();
        // visit the scene
        Node::visit();

        _director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION);
    }

    Camera::_visitingCamera = nullptr;
}

That effectively fixes the crash, and ensures the transitions work correctly, since the camera is now valid for all child nodes of the scene,. Transitions use something like the following calls to output to the RenderTexture:

void TransitionCrossFade::onEnter()
{
...
    inTexture->begin();
    _inScene->visit();
    inTexture->end();
...
}

@halx99 Is this a reasonable patch? Scene::visit() is never called at all except when attempting to render it to a RenderTexture, which is what occurs in the scene transition code. This change shouldn't impact anything else in the engine.

[rh101]

Just some more info. The scene is normally rendered from the glview implementation, for example:

void GLView::renderScene(Scene* scene, Renderer* renderer)
{
    AXASSERT(scene, "Invalid Scene");
    AXASSERT(renderer, "Invalid Renderer");

    scene->render(renderer, Mat4::IDENTITY, nullptr);
}

Inside Scene::render(...), this method is called:

visit(renderer, transform, 0);

So, it never uses the Scene::visit() method at all.

[rh101]

@IcemarkUK PR #1676 is up with the proposed fix for the crash issue.

[IcemarkUK]

Many thanks!