I want to render a pure fire without smoke. I disabled the Enable Smoke Options on Smoke Tab of Karma Pyro Shader. Only enabled the Enable Scatter and Enable Fire options.



1. I found the alpha channel disappeared and aov_scatter and aov_fire didn't get any results.

2. Even if the Enable Smoke option is enabled, the alpha channel is based on Density, Scatter and Temperature are not taking into account, so the rendered alpha is not what you want.



How do I set it up to get the alpha I want? Or customize the alpha channel?

Or is there anything wrong with my understanding? Any help would be greatly appreciated

- Aaron

A purely emissive volume does not have opacity, so no Alpha contribution. You can fake it by binding your Flame to your Density in the bindings tab and set it to a low value. The Pyro post process node can also create a density from your Flame field.