Night/Dayish skydome

[Tannz0rz]

To be honest, I don't know what I'm doing half of the time when it comes to IrrLicht, but I've been messing around today and found this:

Code: Select all

ISceneNode* skydome;
ITexture* skytex;
u8 aph=200;
bool direction;

//==========

void Sky()
{
	u32 size = skytex->getSize().Width * skytex->getSize().Height;
    u16* color = (u16*)skytex->lock();
	u8 n_col;
	video::SColor m_col;

    for(u32 j=0; j<size; ++j)
	{
		m_col.setRed(getRed(color[j])-aph);
		m_col.setGreen(getGreen(color[j])-aph);
		m_col.setBlue(getBlue(color[j])-aph);
		m_col.toOpenGLColor(&n_col);
		color[j] = (u16)n_col;
	}
    skytex->unlock();

	skydome->setMaterialTexture(0, skytex);

	if(!direction) aph++;
	else aph--;

	if(aph >= 255) direction = true; 
	if(aph <= 150) direction = false;
}

//==========

int main()
{
	skytex = driver->getTexture("../draganddroptest/media/skybox/skydome.jpg");
	skydome = smgr->addSkyDomeSceneNode(skytex);
//...
while(device->run()) 
	{ 
		driver->beginScene(true, true, SColor(255,100,101,140)); 
		Sky();
		smgr->drawAll(); 
		guienv->drawAll(); 
		driver->endScene(); 
	} 

	device->drop(); 
	return 0;
}

It creates a rather cool atmosphere, somewhat like the passing of days. Not sure if anyone were to want to use it or not, but I thought that I would just share it with you all anyways.

[3D Ace]

Nice. This will come in handy.

[Virion]

To be honest, I don't know what I'm doing half of the time when it comes to IrrLicht

anyway that's surely something cool.

[sio2]

OMG.

I don't know what I'm doing half of the time when it comes to IrrLicht

Well, you said it yourself...

For educational purposes, here's a few issues:

1. Locking a texture every frame. skytex probably has to travel over the bus to vram after every unlock().
2. calling render() on a scenenode just before the smgr->drawAll() renders it again?
3. Assumed texture format of skytex texels.
4. circumventing Irrlicht's features, namely that this may be better suited to a scenenode

This screams out "replace me with programmable shaders".

[hybrid]

I think the same effect could be achieved if the skybox would give accesst to its mesh, and thus allowing to change vertex colors to something darker.

[sio2]

I think the same effect could be achieved if the skybox would give accesst to its mesh, and thus allowing to change vertex colors to something darker.

A lock and RMW on every vertex in a vertex buffer?

Either a DX5-style fixed-function triadic texture-stage blend or a simple pixel shader would do the trick (even SM1 can handle this)...

[hybrid]

Since the eight vertices of the mesh are anyway sent each frame there's no real benefit by using more than one texture. At least not in general. But I didn't argue that there's no other way, I just gave one other option.

[sio2]

Since the eight vertices of the mesh are anyway sent each frame there's no real benefit by using more than one texture. At least not in general. But I didn't argue that there's no other way, I just gave one other option.

Eight vertices? How many vertices does the default skydome have (see OP code)?

Plus, I'm not suggesting an extra texture. A fixed-function triadic blend op uses a single texture-factor colour per texture stage to be used with the given texture op - the texture factor could be modulated (in hw) per-fragment instead the usual vertex-colour*fragment, for example.

[hybrid]

Well, skydome has some more, but my post was about skyboxes (as explicitly mentioned). Anyway, just provide some code and we'll see.

[sio2]

Well the original post references skydome not skybox.

Anyway, I'm commenting on how poor the snippet is as a general way of going about things. Should we not be educating people about these potential pitfalls?

[hybrid]

Yes of course, hence provide and allow for all "good" ways. But those solutions which require new materials or new shaders should also come with some example code to make it possible for people to use them right away.

[Tannz0rz]

Yes of course, hence provide and allow for all "good" ways. But those solutions which require new materials or new shaders should also come with some example code to make it possible for people to use them right away.

Indeed.

If you've got spare time, an example would be appreciated.