Why did I get two extra prepass of "Irradiance map" in my final render ?

[cc8boy]

I have some questions about the extra prepass in rendering image sequences in Vray 2.40 in MAX 2012 64bit.

Here's my procedure of making my scene.
1. I'm making a complex scene contains some FP objects and RC objects.
2. I put all the forest objects in one "Forest" layer. And I put all the Railclone objects in one "Railclone" Layer. And I put all the other objects in "Another" Layer.

Here's my procedure of rendering my scene.
1.    I unhided all the objects in my scene. And Set my Primary GI engine and Secondary GI engine to "Light Cache". I checked the "Use camera path". I choose the "fly-through" mode in "light cache" and saved the VRLMAP file. I got VRLMAP file After my render.
2.    I set the Primary GI engine to "Irradiance map" and the Secondary GI engine to "Light Cache". I checked the "Use camera path" in "Irradiance map" tab. I choose "Incremental add to current map" mode to save my VRMAP file. I choose the "From file" mode in "Light Cache" tab and choose my VRLMAP file I saved in step 1. Finally I rendered my image sequences every 25th frame. I got the VRMAP file of the "Irradiance map".
3.    I set the Primary GI engine to "Irradiance map" and Secondary GI engine to "None".
   I choose the "From file" mode in "Irradiance map" tab and choose my VRMAP file I got in step 2. I render the real image files finally.

Some FP objects contain some animated trees.
I checked all the materials in my scene. There was no "Refraction_useInterpolation" or "Reflection_useInterpolation" checked in my Vray materials.

My questions are,
1. Why did I get two extra prepass of calculating "Irradiance map" in step 3 of my render procedure ?
2. Why the two extra prepass of calculating "Irradiance map" were gone if I turn the "Forest" layer off ?

[Rokas]

my guess that forest has SSS materials, but might be something else too..

[cc8boy]

I turned on the "override mtl" in "Global switches" tab in Vray Renderer setup page. I set a very simple Vray material as the override material to all the objects. I still got the two extra prepass in the step 3 of my render.

[cc8boy]

I kept searching the FP objects that caused the extra prepass appeared all day long.
I found three objects named "O_Gr_L","Forest Grass L","Forest Grass S" might cause the problem.
If I hid the three objects ,the extra prepass would be gone.

I selected the three objects and run the MAXscript "$.material=undefined" to clean the materials of them. And unhide the three objects.
But the extra prepass appear again ! I am sure there are no material in the three objects now. Why the extra prepass appear again ? I am confused now.

[cc8boy]

my guess that forest has SSS materials, but might be something else too..

Yeah!! Yeah!! You're my savior.
Thanks to your suggestion. I find there are some VrayFastSSS material in the default materials of the grass objects from the Forest Pro Pack library. I think I must check the material from  Forest Pro Pack library extreme carefully.

[Rokas]

I remember Paul saying that iToo gonna replace SSS materials to standard, but I guess they missed some.

[iToo]

I just checked (visually) all materials from the FP 4.3 library and it seems all VRayFastSSS materials were replaced. Perhaps your scene was created with a previous version.
Anyway, if you find some SSS material in the latest release, please tell us and we'll fix it.

[cc8boy]

I have a very important question.
How to remove the material of the Forest Pro Objects thoroughly ?
I tried to replace the VrayFastSSS2 material in the sample objects of the Forest Pro Objects. I'm sure there are no SSS materials in the sample objects. But the original VrayFastSSS2 material still remain in the material of the Forest Pro Objects.
I even used this command "$.material=undefined" before clicking the "Reassign Material" in the Forest Pro Objects. But the original VrayFastSSS2 in the multimaterial of the Forest Pro Objects appear again.
How Can I get rid of the VrayFastSSS2 material in the FP objects completely ?!

[Rokas]

if i understand correctly, to remove materials, You have to do it twice:




Forest uses material in Geometry rollout (red), but if it is empty, it uses original object material (green)

[iToo]

I suggest to edit each material individually, picking them from Geometry->Material parameter. Move it to the Material Editor and make the changes here.
The automaterial assigned to Forest is updated automatically, so it's not necessary to change it.

If you don't want to manage materials from the Geometry rollout, it's possible to remove them using the "Clear" button. In this case Forest uses the material assigned to the Custom Object. But in all cases the automaterial is created and updated, because it's necessary for the rendering process.

[cc8boy]

Can you tell me step by step ? My only purpose is to remove the VrayFastSSS2 in my scene.

1.I edited the materials of my sample objects(get rid of the VrayFastSSS2 in the sample objects). (such as the small clump grass geometries and the large clump grass geometries.)
2.I found the extra prepass still appear.
3.I checked the materials in the forest objects(not sample objects). I found the VrayFastSSS2 still in multimaterials of the forest objects.

It seems that multimaterial of the forest objects would not update after I edited the the materials of my sample objects.
What's the correct procedure to get rid off the VrayFastSSS2 in my forest objects ?

my system is MAX2012 64bit with FP 4.2.4

[iToo]

Please check each one of the materials of the Geometry List (Geometry->Material parameter). There should be some VRayFastSSS2 there. Just replace it and that's all.

Forest works in the following way to compose its automaterial:

a) If there is a material defined in the Geometry list, it is used. The material assigned to the sample object is ignored.
b) When there is not a material assigned (e.g. clicking the "Clear" button), then Forest uses the material of the sample object.

So, in this case you have updated the materials of the clump grasses, but really these are not used because there is a material defined in the Geometry list.
Anyway, it's a good idea to update both, just to be sure there is not any VRayFastSSS2 in the scene.

[cc8boy]

All of my sample objects never miss materials.
Do you mean the materials of the forest object in final render are often combine with the materials in the Geometry list not the materials from the real sample objects ?
The materials in the Geometry list are not instance of the materials in real sample objects.
Do you mean the materials in the Geometry list are just copies of the materials in real sample objects. Changing the materials of real sample objects won't change the materials in the Geometry list ?


Should I always keep the Materials to be "None" in the Geometry list in order to keep the multimaterial of the forest objects change automatically after changing the materials of the real sample objects ?

By the way, how can I batch click the "Clear" button in different forest objects in my scene automatically?

[iToo]

The procedure listed in my previous post describe the generic rules used by Forest to compose the automaterial.
But yes, you are right... both materials can be the same if are instanced, what it's exactly the case when using the library (sorry, i forgot that point).

What it's true is that the material of the Geometry List has precedence (when exists) over the material applied to the object.
If both are the same because are instanced, then obviously the result will be identical if used one or other material.

Usually it's not necessary to set the Materials to "none". But you can do it,  if you prefer to use the materials of the sample objects (and for some reason these are different from the Geometry List).

There is not any procedure to "Clear" all materials from all Forest objects. But you can select multiple items in the Geometry List and apply the Clear button, modifying one Forest object each time.

[cc8boy]

many thanks for your detailed explanation. Now I understand why the materials of the FP objects will not change automaticlly after I change the materials of the real sample objects.