Rendering Sprites Using Arnold

[srbarnes]

I have used Maya for over 20 years and I have a question regarding the rendering of sprite nParticles: is there any existing documentation to which you can direct me that clearly explains how to render sprites using Arnold? I ask because I have been tirelessly attempted to set up a sprite simulation and get Arnold to respect the sprites' opacityPP parameter so that the sprites fade in and out at birth and death, respectively, while ensuring that the sprites' image/texture and its alpha are also respected. Please see the image displayed below.

Can someone direct me toward a person or resource that can better explain how to accomplish this? Please note that years ago before Arnold was Maya's primary renderer one could easily hardware render sprites. Also, do people use sprites any more or are there better solutions? Thank you for your time and assistance regarding this matter, it is greatly appreciated.

[Stephen.Blair · Accepted solution]

To use opacity with Arnold, you have to do this:

• Add "opacityPP" to the Arnold > Export Attributes text box (nParticle Attribute Editor)
• Clear the Arnold > Opaque check box (nParticle Attribute Editor)
• Use an aiUserDataFloat shader to get the opacityPP value, and connect that to the Opacity on an aiStandardSurface

[srbarnes]

Mr. Blair, thank you for the example file and the solution. With the setup that you described and demonstrated in the sample file how would I apply a color texture and opacity texture to the sprite while maintaining opacityPP? For example, I would like to create smoke using sprites. I have an image file that provides the color texture for the smoke and an image file  that provides the transparency texture for the smoke. How should I integrate the those images/textures into my shader network so that opacityPP stills fades out my sprites as they die? Would I use an aiComposite node to combine the "aiUserDataFloat" with the transparency image/texture? Please see the enclosed image. I also included the sprite texture that I am using for both the sprites' color and transparency texture. Thank you for your time and assistance with the matter.