Bump, Displacement & Clip Mapping

[Ibontxu]

Hi to everyone. I'm studying architecture and i've been using sketchup for over 3 years. Until now i rendered my proyects with kerkythea, but i preffer vray. Nevertheless, i have some problems, and i would be very grateful if someone could help me.

1- When i apply an sketchup material to an object and i render, everything goes ok. So, to add bump to that material, i create a new VrayLinkedMtl and i apply a Bump image in Bump channel. Well, at that point if i render the model with an vray light above the object(gi_irmap_medium.visopt) everything goes right, but without the light there is no bump.

2- If i use the same grayscale image in displacement channel (and uncheck bump) and render the model, nothing happens, there's no displacement (although in the update preview the material it show displaced material perfectly). And same with clip mapping (transparent).



3- So, i tried another option: I apply a material in sketchup to a model. Then i create a new material with the vray external material editor using the same texture for difusse and a grayscale of that image for displacement. In sketchup, i import new material and choose the one i have just done. I apply that to the object that had a sketchup material on. That way, the vray material adopts U and V coordinates of sketchup. With Bump & Disp nothing happens, but when i render the model with clip mapping it works.

Apply material in sketchup, link with Vray and modify with alfa:


Apply material in sketchup, make a material in external editor an aply later to the object:



Why happens that? it's like vray couldnt modify sketchup linked material to make displacement or something like that. So everything i would like to insert a tree or people in my model, do i have to insert the image --> explode --> make component --> make face me --> make a new material with the external material editor an apply it to the people/tree? It has to be an easyer way.

4- Is there any way to preview Vray materials when we choose them (i mean all of them like in sketchup, not clicking "Update" in each of them)

Thanks for your help!

[dalomar_cg]

Re: Bump, Displacement & Clip Mapping

1. Bump is going to be very reactive to the direction of the light that is shading the surface (since bump changes the normals of the surface), so in a pure GI type environment you won't really see the bump effect that much. Bump doesn't really change the structure of the surface, only the normals that are used to shade it. So things like self shadowing, which usually adds some articulation of the surface in GI type environments, won't be possible (displacement is the thing for that, see below).

2a. Right now its very hard to get displacement to work because of how SU creates the geometry, and displacement acts directly on the structure of the geometry. I can't remember if its an issue with grouped objects, or objects in components or what have you, but it takes allot to get it to work. Also, add the fact that its a linked material on top of that and it only compounds the possible issues. Joe has been looking into getting displacement to work much more reliably, and hopefully will be improved in the next service release. Setting up displacement, however, is not much different then bump mapping, so chances are you've got it set up correctly.

2b. Right now the best way to do mapping is through SU's texturing tools, but that then requires setting up a linked material, which for integrated alphas (which is how SU takes care of transparency mapping) is not supported by v-ray. So for transparency mapping, the current suggested workflow is to apply a standard SU material with a texture and change the opacity value to 0 (completely transparent), set up a linked material from that SU material, then add your maps to an additional diffuse layer. That way the mapping will still be controlled through the SU texturing, and the diffuse channel can get the correct alpha map. For the next service release, I believe that Joe is changing how the linked material is handled, so you will just be able to add the alpha map directly on the linked layer.

By the way, the only way SU creates UV coordinates for geometry is if it has a texture applied to it (through a SU material), so for anything that requires a texture or texture coordinates, the easiest way is to set up a linked material from a SU material w/ a texture applied. Even if you don't want to actually use that texture.

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

Many thanks for your quick response, Dalomar. Very good idea to get mapping! I'll try soon.

I've been trying to achieve displacement effect and that's what i have done until now:

I don't know if the displacement is what i have achieved, because for displacement map i have used THE SAME TEXTURE as i used for difusse!!! (not Grayscale) ¿does it have any sense?

Aply Material in Sketchup --> Link it with Vray --> enable displacement channel and choose the same texture as difusse:







Aply Material in Sketchup --> Create "grass" material with vray external material editor --> import it in sketchup --> assign to the object:

rendered with rectangulat vray light: (displacement: 5)

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

I'm really frustrated and i`m getting really crazy with displacement maps.

If anyone knows what happens please help me.

Here there are some renders. All of them have been done using the same options.

1- Wall (texture applied in sketchup)




2- Wall with bump (texture applied in sketchup, linked vray material, aplied bump)

--> no bump appears. Exactli same as 1- wall.


3- Wall with bump + Vray Light above it (texture applied in sketchup, linked vray material, aplied bump)




Difusse & Bump



4- Wall with displacement + Vray Light above it (texture applied in sketchup, linked vray material, aplied displacement)
--> no displacement appears. Exactli same as 1- wall.


5- Ground (a plane)with grass aplied in sketchup, linked vray material, aplied displacement(i was wrong, displacement works with difusse & with grayscale)




Difusse & Bump




Why does displacement work with grass and not with wall? if anyone knows please tell me because i have tried thousand of times to understand the program and i cant

[dalomar_cg]

Re: Bump, Displacement & Clip Mapping

Well on the grass you've got the displacement working. As I said previously there are issues with applying the displacement to certain types of geometry, mostly groups and components. I will check up on exactly what those limitations are tomorrow, but don't get too frustrated at it because its not you (its SU and its crazy way of creating geometry).

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

Ok, thanks you for explaining it to me. Now that i know it i will spend my time learning better other aspects of the program. thanks again for your interest

[dalomar_cg]

Re: Bump, Displacement & Clip Mapping

Don't want you to get all frustrated about something thats not your issue.

[jethro.berry]

Re: Bump, Displacement & Clip Mapping

Ibontxu,
I feel your pain with the disp. it is very inconsistent.

What i can offer you is another solution to the transparency map. What i found is that if i make the linked material and then apply the transparency map it doesn't work. But if i then add the same map to the 'background' map on under the map tab in the same way as the transparency map too. It then works...

Jethro

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

It Works!!! It works!!! I don't know how did you discover it but it's fantastic.

Tree 1 (Image imported to sketchup, exploded, made component, linked Vray Mtl with alpha applied = doesn't work)




Tree 2 (Image imported to sketchup, exploded, made component, linked Vray Mtl with alpha applied + Backgroung enabled with the same alpha image = works!!!)




So, now that i know that i have a question: Do i have to do all this process everytime i want to insert a tree or a person in my model? I mean, the only way to make something like our private RPC collection for sketchup is:

-Step 1: Make a collection of trees, vegetation, people or whatever for sketchup (face- me components, like the 1st image tree)

- Step 2: Make a material for each one of those components with the vray external material editor to link to sketchup components when we want to achieve transparence effect.

?????????


Thanks for your way to do clip mapping, jethro.berry!!!

[x-site]

Re: Bump, Displacement & Clip Mapping

yes it works fine... but quite a long process to get there.... lets hope this issue is resolved soon.

Thanks for all the help

[jethro.berry]

Re: Bump, Displacement & Clip Mapping

Cool, I'm glad I could help.

It is tedious but the fact that it is consistent is appealing.

Question for the moderators: Has any progress been made with regards to displacement maps??? Because it seems that quite a few people are having hastes with it....

J

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

I have been investigating about Vray displacement in Sketchup geometry and i've discovered that the result is very different deppending on the steps you follow when applying materials.

I have done 4 rectangle surfaces (500cm x 500cm) called A, B, D & E, and i have followed some steps with them. It's very mportant follow steps in this exact order:

Surface A:
- Apply stone material in SketchUp.
- Create a new Vray Linked Material and add displacement (5)
--> No Displacement




Surface B:
- Select all the surface and make a group or component with it
- Apply stone material in SketchUp (from the outside of the group/component, not editing it).
- Create a new Vray Linked Material and add displacement (5)
--> Displacement with wrong U and V coordinates




Surface D:
- Select all the surface and make a group or component with it
- Apply stone material in SketchUp (from the inside of the group/component, editing it).
- Create a new Vray Linked Material and add displacement (5)
--> Wrong Displacement




Surface E:
- Apply stone material in SketchUp (from the inside of the group/component, editing it).
- Select all the surface and make a group or component with it.
- Create a new Vray Linked Material and add displacement (5)
--> Correct Displacement and correct U & V coordinates!!! (I have to continue working with displacement global settings to achieve a better result, but it's a beggining)

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

Ok,I correct myself. I had the hope to have discovered how displacement works, but i have tried to repeat my own steps 5 min ago and the results were completely different.

So, there's only one certain thing in Vray.

VRAY WILL MAKE DISPLACEMENT ONLY WHEN VRAY WANTS :'(

[dalomar_cg]

Re: Bump, Displacement & Clip Mapping

Thank you very much for posting both your examples and the steps you took to get there. Whether or not it worked the second time around, it will still be helpful to us. If you would also send us the scenes/materials/maps as well that would be helpful to us as well. Geometry in SketchUp is just crazy...and since displacement works directly on the geometry its quite hard to pin down whats going on.

...It may just be me, but it looks as though D and E both produce the correct displacement at least from what I can tell with out looking at the maps and settings. (I don't know whether thats good or bad)

[Ibontxu]

Re: Bump, Displacement & Clip Mapping

Yes Dalomar i think you are right. I think that the only difference between aplying a texture to a group and applying a texture and converting that surface to a group later may be that the origin of the texture changes when you make a group, and it moves. So the displacement would stay the same.

Here's the sketchup file, and difusse & Bump or Disp textures. Again with different results... I have used presets IR visopts. (low, medium...)

http://rapidshare.com/files/53295154...ement.rar.html


One more thing. If you open the file, each time i say "texture applied" i mean sketchup texture applied AND Vray linked material applied too, IN THE SAME STEP. I hope this file would help someone...