Multipass rendering problems

General discussion about Cycles 4D.
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Multipass rendering problems

Post by ciaran » Wed Jan 31, 2018 12:22 pm

I'm having some problems with multipass rendering -
Shadow pass looks terrible and is totally unusable - nothing at all like what I'd expect from C4D's standard renderer.
Object buffers are jagged.

What are the problems here? Any tutorials showing how I can fix this?

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Re: Multipass rendering problems

Post by Canuc » Thu Feb 01, 2018 9:03 pm


I'm not a veteran like a lot of people on this forum, but I got an explanation for you, about all that was written in the forum

I understand the forum is about Cycles 4D and the Blender Cycle core
Bear with me because I found a great explanation in the documentation of the renderer Redshift 3D that relly helps understanding what is going on.

Also: Check out this forum link: viewtopic.php?f=3&t=670

The problem you are mentionning was bugging me and I wanted to understand the question about multi pass and the rendering of object ID's and AOV's.

Multi pass is for rendering the different layers of a frame, like
Diffuse, Specular, Reflections, Refractions, Global Illumination etc...
It gives you great granular adjustment power in the compositor for adjusting your different pass (like more specular or less specular).

Object and the famous Jaggy edges:

In cinema 4D you can assign IDs to objects, so you can produce a mate layer that will permit you to isolate object in your composition. The standard ou physical renderer of c4d will produce a anti alias mate
(his is the temporary solution mentioned in the forum)

For now, in cycles 4D (Blender Cycle core), the only thing that can produce are mate mask with jaggy edges
I'm sure they will have a solution in the near future for this.

Here is the explanation in Redshift and there solution
Again, this is only to understand the jaggy edges problem

Redshift documentation:
ObjectID node
The ObjectID AOV stores the mesh's object ID at each pixel.

The drawback is that it doesn't properly support antialiasing, depth of field or motion blur and can therefore generate
aliasing artifacts in the AOV data. This is because each pixel can hold only one object ID and, by definition, usage of DOF and
motion blur means that multiple objects can 'share' the same pixel.

Redshift have implemented an node called Puzzle Matte AOV that gives a great solution

Redshift documentation:
Redshift allows the assigning of IDs to objects or materials. The puzzle matte AOV allows each of the R, G, B channels to contain the per-pixel contribution of a single object or material. Traditional objectID/materialID AOVs typically hold a single value per pixel which can produce aliasing-related issues when the same pixel can 'see' multiple objects/materials. This is especially true when the scene uses depth of field and motion blur. Additionally, having a single ID per pixel prevents the production of matte masks through reflections or refractions.

The puzzle matte AOV, on the other hand, holds per-pixel contributions of object/material IDs on separate RGB channels, which means the same pixel can 'mix' contributions from multiple (up to 3) objects/materials and be workable even in the presence of depth of field, motion blur and reflection/refraction.

It creates black images with an object with a single coler (R,G or B) that can easily isolate in the compositor (with anti-aliasing)

It was mentioned that the team at Blender cycle core are looking it to AOV's
If they do and implement something similar it's going to be great, because I really like cycles 4D renderer.

I just hope it helps

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