Shaders brighter than white?


#1

Hi guys,

I’m what you might call, a Blender NEWBIE! Today is the first day that I’ve used it and I’ve run into something which may not be solveable, at least for me it’s not anyway.

I’m using Yafray just to do some basic renders (to get into the workflow etc) and here’s one that I’ve come up with:

It’s lit using Full GI (whatever that means!), no photons. The lighting comes from the sky, and from a Plane mesh like a light card. My problem is with the shader for the light card, it seems that all of Blender’s values have locked ranges when it comes to colours. That means that my light card can only have a very limited light strength.

I know I could probably just use an Area light, but coming from Maya where you can have huge crazy values (in the negative also) for most attributes, I’m used to using light cards (or just any object) of whatever brightness I want. You can do that it XSI and Max too (in Max you use an Output Shader to remove the value limits).

Anyway, to get the light card as bright as it is, I turned off ‘Clamp RGB’ and used a Blend texture set to white, with the Brightness set to 2 (the max). It’s mapped to the Color, Emit and Ambient attributes. It’s the best I could come up with, with my whopping 2 hours of experience in Blender. My next idea is to just create a pure white HDR image in HDRShop (or whatever) and apply that to the card instead. I assume that would work anyway.

My question is, is there a better way around this value limiting? Can you turn it off? Or can I map the colour with an expression or something instead?

Thanks!

:bowdown:


#2

humm… I’m not sure about what you are asking for.
Anyway, here is an example about creating lighting areas,

http://forums.cgsociety.org/showpost.php?p=2723858&postcount=17

you should put an emit object above an area light, both of them the same size.

The technique is this one:


#3

Full Quallity Global Illumanation.

As for the FX you want to achieve… do you have a picture (even if made in other software) showing how it should look? )


#4

I did not even a single Yafray render yet but I think you can try to render to XML, and hack it. Maybe it would crash the thing, maybe not. :slight_smile:


#5

i know what you are talking about.

it is currently not possible to make an object into a light source in yafray.

you cannot make an object cast light via the emit value unfortunately. this is one of the things i miss from my old commercial software.

ask for this feature in either the yafray and/or the blender developer forums. if enough people request it, it could become a reality.


#6

Thanks for putting it on plain language.

Now, who said you cann´t? Are you forgetting about the Radiosity Solver? More perhaps more useful now, are you forgetting about the Quick Radiosity Solver? :stuck_out_tongue:

And about making an object whiter than true white, Since 2.40 Blender can save to (will insert name as soon as I recall it) format that stores the full 32 bit buffer.


#7

it is possible, but it’s a bit stupid: You’d have to apply a hdri texture to the object… (which can be plain white of course)


#8

it is possible, but it’s a bit stupid: You’d have to apply a hdri texture to the object… (which can be plain white of course)

does this work? i’m going to try it when i get some time.

apollux, does the radiosity solver turn an object into a light source?


#9

In any renderer that uses irradiance mapping/final gather or quasi monte carlo path tracing, it should be possible to use a very bright object as a light sourse, because the renderer is just doing a very bright white colour bleed effect from the “light” to the other objects.

It works fine in Blender with Yafray, just you can’t really control the “light” brightness very well because of the value limits. Unless you use a HDR texture, which I still haven’t tried yet.

Here’s my Blender scene rendered from a different angle, to see what’s happening:

:thumbsup:


#10

yup, that is (kind off) how it works.


#11

Yes, I would also like to be able to push the values further. It seems kinda odd to me that the lights only go up to 10 intensity. Hopefully this gets updated, Blender just keeps getting better and better :slight_smile:

P.s. What is actually happening with the GI when you don’t have the irradiance cache or photons turned on? Is it full Monte-Carlo GI? I can’t seem to find this in the docs anywhere.


#12

FYI, YafRay is being rewritten completely (at least they’re planning to!). It’s a big thing, but the devs decided not to work with the old code (=not a very good/scalable framework) anymore. This makes yafray lag a bit behind Blender, but all for the good cause.

Anyway, I think for YafRay expertise, you should visit the YafRay forum. Not to bonjour you away, but the devs regularly read that forum, and they are probably able to help you much better! Do make sure to report back here though :slight_smile:

I will try to answer your question if you could show a picture of the effect you’re trying to get. From my experience it’s usually the most effective to put the lights very far away from the scene to avoid bright spots like the one currently in your picture (make sure that you scale up the emitting object correspondingly aswell!!!). Then you can use EmitPwr in the YafRay panel to control the light intensity.
edit: this is a workaround though, since the EmitPwr value scales ALL the emitting things (world, arealights & emitting objects). This means you’ll probably have to scale these down.

BTW, as a maya user you’ll be happy to know that a node editor is being worked on, as a basis for many things (materials, compositing etc.)


#13

Yeah, that’s the problem unfortunately! If I move the emitting object further away the light dies of much too quickly and I get no light from it. Removing the colour value limits would allow total lighting freedom really.

Cool! Thanks for the info!


#14

Render with Yafray and the XTML option.

Open the XTML file with any text editor and find the Lamp settings.

Push the value as far as you want !

:thumbsup:


#15

I’m using Yafray just to do some basic renders (to get into the workflow etc)

If you want to get into YafRay workflow, take a look here:
http://www.blender3d.org/cms/Alejandro_Conty.450.0.html


#16

I didnt understand what you mean untill I tried this. It seems a material with an emit value will be a light but the power is limited every thing I try to do to up its power also ups the gi power or exposure of the whole render.


#17

I’m YafRay documents, a material with an emit value is always in company with an area light of the same size. The arealight is actually the photon emitter:
[ul]
[li]Material with an emit value[/li][/ul]

[ul]
[li]Material with an emit vaule + Arealight[/li][/ul]


#18

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