Render Passes Discussion

[linvanchene]

obsolete post edited and removed by user

[prodviz]

'Which layer blend mode would you use in photoshop to composite a reflection pass?'

In 32bit a reflection pass would be set to Add and in 16bit to Screen.

[gristle]

A few years ago I dabbled with the pass export in Kray.

The formula to get the same as a flat export is...

(caus+dire+indi)*txtr+othr+lumi+refl+refr

Add/Linear dodge is the blend mode for the reflection.

Of course, it only works correctly in 32 bit/channel, as I found out after a little frustration.

Maybe if it would help the Devs, I can render out a test scene in Kray and supply the layered PSD?

[prodviz]

V-Ray has this set up in Photoshop:
RGB Colour: Normal
VRaySelfIllumination: Linear Dodge (Add) VRaySpecular: Linear Dodge (Add) VRayReflection: Linear Dodge (Add) VRayRefraction: Linear Dodge (Add)
Diffuse + Lighting (Group): Linear Dodge (Add) VRayRawLighting: Multiply
VRayDiffuseFilter Copy: Normal
Diffuse + GI (Group): Normal VRayRawGlobalIllumination: Multiply VRayDiffuseFilter: Normal

The last time I used Mental Ray all layers were set to Add in 32 bit. Although this always gave burnt out highlights.

Maxwell is additive for Multi Light.

[illidsch]

The last category (layers) is the one that proved to be the most controversial and lots of different ways are being proposed to do basically the same (at least how we understand it): Getting out an image (or multiple images when render passes are used) that shows only part of the scene plus its "side-effects" on the rest of the scene.
Please let us know if that makes sense to you.

I think this is the right way to go!

Concerning shadows and reflections - I composited last week a shot with c4d Passes exactly the same way you suggested.

Only downside to this type of renders are the "missing" pixels. If you for example would blur the reflection in compositing, at a certain blur strenght the picture would fall apart. You could see that the the reflection is not filling the pixels where the ring overlaps. But this is a common problem in 3D. Only solution is to render every pass separate.

Since Octane is a physical Render: Doesn´t it actually calculate "all" of the reflections, no matter if they are obscured by another object or not? If so, would it be possible to render the "layer" passes out so that no pixels where missing for compositing?

[geo_n]

various rendered layers and mask (sometimes multicolored Object and Material ID renders and other times alpha masks) that were rendered out.

The multi colored obj/mat id matte we have now would be better if we can control it manually not just automatically. This is one of my request.

After some pondering, we came to the conclusion that there are actually 4 groups of images or results that people want to see coming out of a rendering with render passes:

• Beauty passes: Splitting up the contributions of an image by the material/BRDF type and by direct and indirect paths. This allows further tweaking of the rendering by modifying/filtering those contributions.
• Info passes: Providing additional information like normals, Z-depth etc. to compositing tools to do some more advanced compositing/image processing.
• Lighting passes: Splitting up the contributions of an image by light sources to allow tweaking the lighting after rendering.
• Layers: Splitting up the scene into separate parts and then use them to combine renderings of those parts with other images from other sources (photos, drawings, renderings of other engines, you name it) using compositing.

The first two categories are pretty clear for us and are basically what we have already and we are going to improve that system. Lighting passes are also pretty clear to us and it will probably be straight-forward to implement them.

The last category (layers) is the one that proved to be the most controversial and lots of different ways are being proposed to do basically the same (at least how we understand it): Getting out an image (or multiple images when render passes are used) that shows only part of the scene plus its "side-effects" on the rest of the scene. What does that mean? Let's look at this simple example:

resting_ring_Beauty.png

Imagine you want compose the ring and the box onto some background. In that case you probably also want to be able to take over the shadows, caustics and the reflection on the floor, but not the floor itself. That's the "side-effects" I mean, i.e. effects the geometry of a layer has on the rest of the scene that is not in the layer. If you just cut the geometry, but leave out the side-effects and compose it onto some other image the result would always look wrong. And all these things are not doable with simple masks you derive from some object/material ID pass.

So what can we do? The idea is to select a sub-set of the scene geometry and call it a layer. Our plan would be to give each material/object layer node a layer ID pin, which would just be a number and all geometry that has the same layer ID assigned would be part of the same layer. Then in the render target you would specify the layer you want to render (by selecting its ID) and if it would be inclusive (i.e. everything in the layer) or exclusive (i.e. everything NOT in the layer). To get the ring and the box of the example above, I would put the ring and the box into the same layer and select that layer inclusively or put the floor into a different layer and then select the floor layer exclusively. During rendering we would then consider everything that is not part of the rendered layer to behave similar to a matte material, i.e. it would be invisible but would still "receive" the side-effects of the layer geometry.

Yes sounds good! From what I understand we will have assignable object/mat ids with your plan. Excellent. Why call it pins though?

I'm very excited about this if its actual ids! Lightwave doesn't have proper object/matt ids unless you go the rgb route(mutli-color mask via dpont plugin or kray) or extrader. But they were never assignable so sometimes they fail. So this octane feature of manual assignment is good to have.

I think you need to tell this guy he will not be confused with his fusion workflow anymore when you update octane.
http://render.otoy.com/forum/viewtopic.php?f=76&t=43278

[geo_n]

Is the z-depth in Octane Standalone not anti-aliased?

I did some filtering with the z-depth and noticed the 'jaggies'.
Ended up blurring the z-depth to get rid of them.

Zdepth shouldn't be AAd. Two pixels side by side with different depth info that is AAd will have wrong info producing halo effect. You can feather it but its much better to have coverage buffer that fixes this issue.

[geo_n]

Please fix the shadow issue on the matt shadow material. Objects or lights that have "don't cast shadow" checked should not have its shadow "caught" by the matt shadow material.

[CarloJongen]

Hi Geo,

In the next link you can find all the files for the LW-Octane Fusion workflow:
https://www.yousendit.com/download/UlRS ... N0JjR01UQw

There are 3 rendered frames included in the files, so people who don't have LW-Octane or Fusion can still experiment with there Compositing Software.

Greets,
Carlo

[momade]

Is the z-depth in Octane Standalone not anti-aliased?

I did some filtering with the z-depth and noticed the 'jaggies'.
Ended up blurring the z-depth to get rid of them.

Zdepth shouldn't be AAd. Two pixels side by side with different depth info that is AAd will have wrong info producing halo effect. You can feather it but its much better to have coverage buffer that fixes this issue.

im not familiar with coverage buffer. could you explain how this would improve zdepth?

sounds very interesting.
br.
mo