render in layers...reflection..HOW?

[yolao]

i made a test by assigning a blinn material to all the objects in the reflection layer and then turn the color to black, then i do obtain a reflection layer, but the reflection does not look exactly the same as in the main render.
Even if i already try diferent blending modes...

[buzzman]

Try this:

create a render layer, add the reflective geometry (make sure it has a reflective shader like a blinn, phong, etc), add the geometry that is going to visible in the reflections. Add your lights. Go to the render stats of each geometry item that is going to be visible in reflections and turn off primary visiblity, turn off cast and receive shadows, then for each light turn off emit diffuse and emit specular. Render away.

[mindsample]

As far as I am concerned the Maya Specular Pass is incorrect as it cancels out any diffuse component within the render therefore does not produce correct reflections of diffuse elements within the scene - unusable in any pipeline.

In fact going with the specular render pass the actual diffuse color of any object in the scene becomes redundant as it does not affect the computation of the image at all - which is quite paradox considering that this pass is supposed to easily provide the reflective components of an image.

The only way to do this at the moment is by hand, which involves ridiculous amounts of work. A scene with three objects requires three individual renders, each with the "other" two objects primary visibility switched off and the "first" objects diffuse component turned to zero.

[yolao]

hi guys

thanks for the input.

i made some tests with an sphere a couple of lights with cast shadows and an hdri map with FG on.

i made four layers in this order on the render layer menu

* reflection = screen blend mode

http://i45.photobucket.com/albums/f86/yolao/3d%20images/reflectionlayer_screenblendmode.jpg

* specular = screen blend mode

http://i45.photobucket.com/albums/f86/yolao/3d%20images/specularlayer_Screenblendmode.jpg

* shadows = normal blend mode

http://i45.photobucket.com/albums/f86/yolao/3d%20images/shadowsAlphalayer_normal_blendmode.jpg

* difuse = normal blend mode

http://i45.photobucket.com/albums/f86/yolao/3d%20images/difuselayer.jpg

then this is the end up comp of the four

http://i45.photobucket.com/albums/f86/yolao/3d%20images/finalcomp.jpg

and the original master layer render

http://i45.photobucket.com/albums/f86/yolao/3d%20images/masterlayer.jpg

you can see that in the final comp render the fg effect is in some way lost, the shadows are darker and the highlights and reflection on the sphere are not as bright as in the original render.... in short there are things that are lost in the final comp render.

please any help is appreciate.
thanks

[Gal]

think about the fact that fg acts as illumination, additive not subtractive(multiply) shadows as you did in comp. and the problem with render layers in maya is you dont get the exact separate passes but mixed. so if cast shadows is mixed with FG .. you will lose FG illumination if u use multiply on your shadow pass. solution is using FG on diffuse pass but you want control over it. the best way is to create your own manual passes not use the maya render layers/passes.
some things are tricky to do, like refractions/transparent objects since you will need a matte pass of the transparency over passes like shadows,fg..etc'.

[temo]

there is ctrl_buffers link somewhere in the forums, its for mental, and its customizes the passes, through buffers

however, I have to mention that, separating to passes and then compositing isnot meant to lead to the same result as the original render without the passes. on contrary - it suppose to give you the control - to lead to a different result that you control and change, sometimes from scene to scene. and of course to show your artistic taste and understanding

from my experience (ye, I tried it too...) - there is no way to achieve a technique with separating to passes and compositing, that will give you the same result consistently throughout different scenes and setups, that results in image that is the same as original no passes render.
I hope I understood you question

temo
-------------------------------------
http://www.sapir.biz

[jeremybirn]

If you want a reflection pass that includes reflections of shadows, reflections of diffuse shading, as well as reflections of specular highlights and other reflections, then one option is to extract it via a "difference" blending mode. Just render one pass with reflections, one pass without reflections, then a difference between them will isolate a reflection pass (reflection pass shown on left in attachements below.)

-jeremy

[MasonDoran]

heh...that trick is amazing! I do the same when I want i want to do FG/GI passes.

[mindsample]

If you want a reflection pass that includes reflections of shadows, reflections of diffuse shading, as well as reflections of specular highlights and other reflections, then one option is to extract it via a "difference" blending mode. Just render one pass with reflections, one pass without reflections, then a difference between them will isolate a reflection pass (reflection pass shown on left in attachements below.)

-jeremy

Jeremy, I had the same idea a while ago but never actually tried to use it as the thought of rendering two very computationally expensive passes (beauty and diffuse) to receive a result that maya _should_ provide out of the box really frustrates me ...

[yolao]

If you want a reflection pass that includes reflections of shadows, reflections of diffuse shading, as well as reflections of specular highlights and other reflections, then one option is to extract it via a "difference" blending mode. Just render one pass with reflections, one pass without reflections, then a difference between them will isolate a reflection pass (reflection pass shown on left in attachements below.)

-jeremy

thanks a lot everybody for the help

Jeremy thanks for the render samples.

I`m totally new with render and render layers, so i have the reflection layer wich i obtain just by excluding the lights of that layer, then i made a NO reflection layer that i did by overwriting the reflectivity if the materials to 0... then i take the 2 pictures to photoshop and i do have now reflections and FG effect but is kind of dark in some places.

I put the reflection on layer first and the highlight with NO reflection layers at top and i use soft light blending mode....

Can you explain more that diference mode that you talk about please.

thanks

[jeremybirn]

thanks a lot everybody for the help

Jeremy thanks for the render samples.

I`m totally new with render and render layers, so i have the reflection layer wich i obtain just by excluding the lights of that layer, then i made a NO reflection layer that i did by overwriting the reflectivity if the materials to 0... then i take the 2 pictures to photoshop and i do have now reflections and FG effect but is kind of dark in some places.

I put the reflection on layer first and the highlight with NO reflection layers at top and i use soft light blending mode....

Can you explain more that diference mode that you talk about please.

thanks

Difference is a blending mode in Photoshop (and most every other compositing program.) It is just like subtraction. It gives you black where the images are identical and the difference where they are not identical. Try it with the images I attached (the two on the right) and you'll see. Apart from turning off the reflectivity, the two layers should be 100% identical in every way, you don't want different lights or anything else to be different.

-jeremy

[yolao]

Difference is a blending mode in Photoshop (and most every other compositing program.) It is just like subtraction. It gives you black where the images are identical and the difference where they are not identical. Try it with the images I attached (the two on the right) and you'll see. Apart from turning off the reflectivity, the two layers should be 100% identical in every way, you don't want different lights or anything else to be different.

-jeremy

thanks a lot Jeremy, i open the two pictures in photoshop and i put the the one with the reflections on top and the other down and i test one with difference blend mode and the other with exclusion, and i did not obtain good results in any...

differnce blend

http://i45.photobucket.com/albums/f86/yolao/3d%20images/Difference.jpg

exclusion blend

http://i45.photobucket.com/albums/f86/yolao/3d%20images/exclusion.jpg

please, what do i have to do.?... i just open one picture in PS and then the other, i create a new layer in one of the pictures and copy paste the other picture to have both in the same scene and then i just test the two blend modes....

any thing that i miss here?

thanks again for the help

cheers

[jeremybirn]

You may have figured it out already because it's been an hour, but put the two images together as layers with the top one set to "difference." :)

-j

[yolao]

thanks Jeremy for your help. i really appreciate that:).

Well, i don`t know what i`m doin wrong here, i did what you said one layer in top of the other in PS and the top one with difference blend mode...

take a look:

http://i45.photobucket.com/albums/f86/yolao/3d%20images/layers.jpg

so....??... i don`t know PS well but i think i have the two layers in the right place, but obviously something is wrong.

thanks again for the help.:thumbsup:

[jeremybirn]

Use the 2 images on the right. The one on the left is just the result you'll see.

-jeremy

[yolao]

Use the 2 images on the right. The one on the left is just the result you'll see.

-jeremy

thanks Jeremy, yes, i was using the ones from the left, is just that i though that you where showing the pictures from left two right in order, so left reflection, the next one: no reflection and the last one in the right the ending result.

The result that i obtain now is like in your first picture on the left.

one question, so the reflection pass on the right is just a normal render with everything?.... i mean, it has light, color, relection, etc.... the only one that have changes are the one with no reflections?

thanks

[jeremybirn]

The image on the left (the one you create via a difference operation) is the reflection pass. A reflection pass is an image showing just the reflections, nothing else.

The other two are identical, normal renders, just one with reflections, one without.

-jeremy

[yolao]

The image on the left (the one you create via a difference operation) is the reflection pass. A reflection pass is an image showing just the reflections, nothing else.

The other two are identical, normal renders, just one with reflections, one without.

-jeremy

thanks a lot Jeremy, wonderful help:thumbsup:... if you have some time i made a question in your lighting render eye thread.

Cheers

[Ash-Man]

jermey's idea is defnatly simple and easy

I was thinking to do anothe approach though
put eveything on a layer > then over ride then over ride the visabilty
pick the plane and over ride "the oeveride"
Maya will complain and not render cause that att is locked
so with a small MEL
you unlock it then turn it ON and use that MEL as pre render



setAttr -l false "pPlaneShape1.primaryVisibility";
setAttr "pPlaneShape1.primaryVisibility" 1;



it's just an idea ..might help

[yolao]

jermey's idea is defnatly simple and easy

I was thinking to do anothe approach though
put eveything on a layer > then over ride then over ride the visabilty
pick the plane and over ride "the oeveride"
Maya will complain and not render cause that att is locked
so with a small MEL
you unlock it then turn it ON and use that MEL as pre render



setAttr -l false "pPlaneShape1.primaryVisibility";
setAttr "pPlaneShape1.primaryVisibility" 1;



it's just an idea ..might help

thanks a lot Ashraf for the help, i`m goin to try that out.

Also if anyone has an idea of how to set a render pass for hair (shave and haircut), please talk about it..

I have an scene that is a bit big in memory and it never finish to render because of the hair, so i will like to render the hair in other pass but still have the shadows that produce on the other surfaces.

thanks

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