Lights and Material configuration

[filoxgeox]

Hi,

we try to use embree engine, it's very fast and clear. We use xml method to export the scene.

But we find some problem with light and material.

Why the source code don't use Ka parameter of material? there is some part of source code that calculate automatically the (Ka) ambient parameter of material? It seems that is used only a factor Kd, and not Ka & Kd , it's possible?

The scene is very dark in parts distant from the light and very bright in places near the light, there seems to be a lot of contrast caused by an ambient factor of the material is too low.

It seems that instead with hdrilight work better and the light is spread more evenly. But unfortunately 99% of our scenes are indoor and we use pointlight and spotlight.

Can you help us to resolve this problem?

Probably the same problem, but let's see if we put a pointlight the distance of the light emitted is low, we must greatly increase the intensity but then we always have a great contrast between the places near the light and places distant the light.

We cannot calibrate well materials and lights so that light is spread evenly in the scene, can you help us for this?

example of wall material parameter is:

"Obj"

"COL5.PPM"
"COL5.PPM"
0.5882 0.5882 0.5882
0.6882 0.6882 0.6882
0.0000 0.0000 0.0000
0

Regards

[SvennW_Intel]

Embree is not a full featured renderer and it kept minimalistic. Embree further is physically based and the often used ambient term is a hack to mimick global illumination calculations which Embree can do directly. The images Embree renders are more less what you would also get in real world when doing your lighting setup.

However, you could extent Embree with the ambient term by adding it to the value returned from the eval function of the Lambertian BRDF.

An alternative might be to use larger area lights to light the scene.

[filoxgeox]

Hi, thanks for the answere, the problem was mine when i export the face normal....i just resolved it and the global illumination is ok now (see attached file, all parameter is not perfectly correct, i have to made it, but the result is more better).
Another little question, in the attached file scene the main illumination of the room is a spotlight, i've created the glass material by obj code, if you look the image you can see that the shadow of glass objects are solid, seems that the light (only spotlight and pointlight) does not go beyond the glass...exambpe the shadow of objects on the left of image. (sorry for the bad english, i hope you understan what i write)
Can you give me some advice how to fix this?

Thank you very much

[SvennW_Intel]

I think you attached the wrong image.

Anyway, the caustics of the glass cannot look right for a spotlight, as the pathtracer has no change to hit the spotlight with paths going through the glass. Photon mapping would not have this issue, however, it is not supported in Embree.

You have to use a large area light source in order to get caustics.

[filoxgeox]

Why the wrong image? Is not a white kitchen that you see?
I ask for glass and spotlight because i use the same material for a windows an with distantlight or hdrilight the light rays going through the glass, but is not important.
Thank you very much

[Dorian_C_]

I edited my original post because I found (by reading the forum) two points to keep in mind.

A pointlight will cast a shadow through glass because large light sources are needed. Also because Embree is minimalistic in it's approach.

I also realize it wasn't intended to be a fully functioning RT, so my apologies for the original post. (which is now withdrawn).

LOVE the raytracer - I added jpeg processing and added to the commands and obj definitions. The results always come out natural and faster than blazes. To have that speed and not be limited by the memory limitiations of GPU's is a real boost!

Awesome work guys! Thank you for providing it.

Dorian

[SvennW_Intel]

The Embree example path tracer does not support rendering caustics caused by a point light. Replace the point light be a large area light and the caustic will be visible.