Rendering Particles Opacity with Arnold

[iztov]

Trying to render particles which fade over time. OpacityPP looks fine in the viewport but won't render with Arnold. At Solid Angle I just found this: 

"OpacityPP with particles will only be exported if the Opacity in the Arnold section of the particleShape is disabled."

Not working though. Anyone any idea how to render particles in Maya 2017 that fade with Particle Age? 

Thanks. 

[mspeer]

Hi!

Replace the default material (npPointsBlinn) with an ai material (aiStandard).

[iztov]

Hi,

I already tried to replace the Blinn Material with an aiStandard. Not working either. The opacity doesn't appear in the render. 

[mspeer]

Hi!

Here it works (by replacing the connection or using it for render only by connecting to Ai Surface Shader), please provide more details about your setup.

Do you have latest Maya and Arnold update, do you use nParticles or Legacy Particles?

Please upload a scene-file.

[iztov]

Hi,

so it is possible ... mooi! (nice) .. 

I did change the BlinnMaterial to an aiStandard, giving me the Out Color Connection (from aiStandard) to Surface Shader as seen in the Hypershade.

I also unchecked the opaque option in the Arnold tab in the nParticleShape1. 

In the viewport I see the opacity, however it does not appear in the render. 

I used a ramp in the Per Particle (Array) Attributes for RadiusPP (works perfect) and for OpacityPP ... 

Thank's in advance

[mspeer]

Hi!

1. There is one connection missing on your scene, from particleSamplerInfo to AiStandard, "Out Transparency" to "Opacity", see the screenshot from my previous mail.

2. If you use nParticles there is no need to use an external ramp for opacity, the functionality is already built-in.

nParticleShape -> Shading -> Opacity Scale (set Input to ...Age)

http://help.autodesk.com/view/MAYAUL/2017/ENU/?guid=GUID-A4496179-B644-428E-885B-C0F587656D25

Also nParticleShape -> Particle Size -> Radius Scale is built-in.

http://help.autodesk.com/view/MAYAUL/2017/ENU/?guid=GUID-7D8F9279-9028-41A1-847B-9D83A3E39358

3. Set Shading (Particle Render Type) to "Spheres" for a proper Preview in Viewport if you this Render Type with Arnold.

[iztov]

Hi,

again thanks,

still having some issues though, 

1. May be silly but I don't seem to have a opacity input in my aiStandard1, 

2. I did tried the internal ramp option before, it's working for radius and color, but  again, not for opacity ... 

[mspeer · Accepted solution]

Hi!

1. There are multiple solutions to connect to the opacity Attribute.

One way is to make all attributes visible (right-mouse-click on node: "Show All Attributes"):

http://help.autodesk.com/view/MAYAUL/2017/ENU/?guid=GUID-23277302-6665-465F-8579-9BC734228F69

You may refine with entering "opa" in the filter field.

2. The internal ramp will work if the connection to opacity is made.

[iztov]

Quite some workaround, but it adds in the magic, at last ...  

Thank you so much! Learned a lot! 

Kind regards 

Iztov

[iztov]

Still not a big fan of the Arnold Renderer though. Giving me strange artefacts where the smoke particles really should be totally opaque in the end ... Spheres probably aren't a good solution for a smoke trail ... 

[mspeer]

Hi!

You are right "solid" spheres are not very good for a smoke trail. But you can remove the artifacts by setting a higher value for Transparency Depth.

Render Settings -> Ray Depth -> Transparency Depth (set to a higher value)

https://support.solidangle.com/display/AFMUG/Ray+Depth

[iztov]

Transparency Depth 8 versus 25 ... 

Render times stay manageable ... 

Neat! 

Giving me options ... 

Thanks again!