Mental ray render issue in 3ds max
I'm learning rendering with Mental Ray and discovered that when I turn on "Photon Mapping (GI)", I get this really bright glow around the hair planes. I don't have Self Illumination on, just a diffuse, specular, specular color and normal bump maps for the hair mesh.
On the other hand when I don't enable GI, I get the really hard and unrealistic shadows like in render 1.
I had about 5 lights in the scene, 2 in back, 3 in front. I deleted all but 2 lights as I feared maybe too much illumination was the cause, but still. I tried also messing with the GI settings but to no avail. Any hints would be helpful!
On the other hand when I don't enable GI, I get the really hard and unrealistic shadows like in render 1.
I had about 5 lights in the scene, 2 in back, 3 in front. I deleted all but 2 lights as I feared maybe too much illumination was the cause, but still. I tried also messing with the GI settings but to no avail. Any hints would be helpful!
Replies
Mental ray (except of the unbiased iRay) only uses a biased GI, so you need to filter the GI (blend the photons together) to get nice results.
For the beginning you could try to only do it using Final Gather. Its a GI calculation too but allows you no caustic effects.
When I use only Final Gather, I do get more realistic shadows (instead of the hard unrealistic shadows that happen without GI), but the shadows still seem a little harsh. But when I enable photon mapping (GI) along with FG I get a bright glow around thin geometry such as hair planes.
Would you recommend I just increase the FG setting or? Turning on "far attenuation" for the lights and moving them farther away from the meshes doesn't seem to help either.
And why are you using "hair planes" and no real hairs? This glow could be because you are using alpha planes. Have you set up your material right? In the mental ray materials there are two slots. One for transparency and one for cutout. You need to place your alpha image in the cutout. The transparency defines the refractive parts of the material.
The reason I'm not using real hair like hair & fur system is because that takes so long to render, and also, I may at some point want try getting into game development and want my characters to have hair planes for game engine compatibility.