[no bug] Light is weird, it looks so rectangular

pandaben7890 · Post by **pandaben7890** » Mon Nov 23, 2009 3:47 pm

I think my light is gonna be circle or something that's look more beautiful.

Did i do anything wrong on my code?

void InitialLight() {
	//------ World Ambient Light--------
	smgr->setAmbientLight(SColorf(0.2,0.2,0.2));

	//------ Set Light Data --------
	SLight data;
	data.AmbientColor = SColorf(1.0f,0.6f,0.7f,0.0f);
	//data.AmbientColor = SColorf(1.0f,1.0f,1.0f,1.0f);
	data.Type = ELT_POINT;
	data.Radius = 1024.0f;
	data.CastShadows = true;

	//------ Add Light --------
	light = smgr->addLightSceneNode();
	light->setLightData(data);

	//------ Attach Billboard to Light --------
	ISceneNode *bill = 0;
	bill = smgr->addBillboardSceneNode(light,dimension2d<f32>(100,100));
	bill->setMaterialFlag(EMF_LIGHTING,false);
	bill->setMaterialType(E_MATERIAL_TYPE::EMT_TRANSPARENT_ALPHA_CHANNEL_REF);
	bill->setMaterialTexture(0,videoDriver->getTexture(PathMedia("fire2.png")));
}

pandaben7890 · Post by **pandaben7890** » Mon Nov 23, 2009 5:07 pm

Is ELT_POINT worth to use?

hybrid · Post by **hybrid** » Mon Nov 23, 2009 5:14 pm

No, you need a working image hoster. All your images are broken.

pandaben7890 · Post by **pandaben7890** » Mon Nov 23, 2009 5:23 pm

I just update a new one with many tris. But not really that circle.
It has a circle-shaped but many edges around.

Ps. Sorry for my bad English TT

hybrid · Post by **hybrid** » Mon Nov 23, 2009 7:38 pm

Could be that your normals are broken or you don't use NORMALIZE_NORMALS wen scaling your mesh. But besides such issues, you'll always get some artifacts without per-pixel lighting.

pandaben7890 · Post by **pandaben7890** » Tue Nov 24, 2009 6:28 am

Code: Select all

model.node->setMaterialFlag(E_MATERIAL_FLAG::EMF_NORMALIZE_NORMALS,true);

I try this after you tell me, but nothing changes TT

vitek · Post by **vitek** » Tue Nov 24, 2009 6:45 am

Read carefully...

hybrid wrote:you'll always get some artifacts without per-pixel lighting.

BlindSide · Post by **BlindSide** » Tue Nov 24, 2009 11:59 am

I dont think those are just per-vertex lighting artifacts however, there is absolutely no attenuation (It gets cut off due to radius before getting a chance to attenuate).

I encountered similar issues and solved it by setting attenuation manually after applying radius but I haven't had a chance to take a look at the engine code that might be causing this problem.

EDIT:

Try this:

Code: Select all

lightNode->setRadius(lightRadius);
		lightNode->getLightData().Attenuation = vector3df(1.0f, 1.0f / lightRadius, 1.0f / (lightRadius * lightRadius));

EDIT2:

What's strange is that MSDN does suggest this:

Typically, an application sets Attenuation0 to 0.0, Attenuation1 to a constant value, and Attenuation2 to 0.0.

So if that does indeed fix the problem then I'm at a loss as to why.

EDIT3:

The formula that the GPU uses to calculate the strength of a light at a vertex is:

Code: Select all

Atten = 1/( att0i + att1i * d + att2i * d2)

Now assuming that att0i and att2i == 0, the light radius is 5 and att1i is set to 1/5, at 0 distance we get "1/(1/5 * 0)", which is infinity. As we approach the light's border, at distance 5 we get "1/(1/5 * 5)" which is equal to 1 exactly.

Basically what this means is that the attenuation factor irrlicht is currently using (0, 1/d, 0) would provide a light strength of > 1 everywhere inside the light's radius, leading to the artifacts visible in that screenshot (That being, an instant cutoff).

Surely I am missing something here. Either the MSDN docs are suggesting something ridiculous or there is another cause for this issue.

I am moving this to bug reports as I'm almost certain there is something wrong here.

EDIT4:

Oh yeah, I just noticed that you set the radius using SLightData and not using ILightSceneNode::setRadius (And therefore the attenuation factors did not even get calculated). If this solves your issue then I guess we don't have a problem here.

pandaben7890 · Post by **pandaben7890** » Thu Nov 26, 2009 3:15 pm

Wow! It's work.

Atte makes light as it should to be.

Thank you for your answer, your answer is really perfect.. ^^

"Kop Koon Kub" ^^

BlindSide · Post by **BlindSide** » Fri Nov 27, 2009 5:25 am

Ok I guess I need to make a test case for this.

Did you try doing setRadius() on the ILightSceneNode without setAttenuation (Like I said in edit 4)? If that also solves the problem then I guess there is no bug.

Cheers

pandaben7890 · Post by **pandaben7890** » Sat Nov 28, 2009 8:16 am

yeah i already did test it. I think that use .AddLightSceneNode(blah blah blah) is equal to .AddLightSceneNode() and then set SLight by myselft.

But it's not, it likes .AddLightSceneNode has its own way to calculate many things like "Attenuation" in its function. ^^

Thanks a lot.

hybrid · Post by **hybrid** » Sat Nov 28, 2009 12:44 pm

No, just read the documentation of SLight. You are not supposed to use many of those fields, they are only for internal purpose. There are methods in ILightSceneNode to alter those values.