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It is emissive. Feel free to reference the original Porter Duff paper regarding "luminescent pixels" or Alvy Smith's opinion on the matter as relayed by Zap An

It is emissive. Feel free to reference the original Porter Duff paper regarding "luminescent pixels" or Alvy Smith's opinion on the matter as relayed by Zap Andersson in the legendary Adobe thread. https://forums.adobe.com/thread/369637 https://forums.adobe.com/thread/369637 Here is a sample of the candle referenced by Zap: https://i.imgur.com/bnXyAl1_d.jpg?maxwidth=640&shape=thumb&fidelity=high https://i.imgur.com/bnXyAl1_d.jpg?maxwidth=640&shape=thumb&f... Remember that a ray tracing engine uses associated alpha as that is the sole format it can generate. Only associated alpha models emission and occlusion. Further reading: http://lists.openimageio.org/pipermail/oiio-dev-openimageio.org/2011-December/004709.html http://lists.openimageio.org/pipermail/oiio-dev-openimageio.... https://groups.google.com/forum/m/#!topic/ocio-dev/ZehKhUFqhjc https://groups.google.com/forum/m/#!topic/ocio-dev/ZehKhUFqh...

dahart 9y ago
> It is emissive. Yes you're right; I wasn't arguing with you about that. I always feel like calling it additive rather than emissive. But just because you can represent additive colors in premult images doesn't mean you should, and I'd speculate wildly that it occurs less often in production than halo problems. Someone who writes lens flare and rainbow shaders is going to scold me for saying that though... In the context of the OP's article, and of artists who paint images with transparency in them, worrying about emissive colors isn't really an issue. Artists very rarely paint pre-mult images, they can't work with premult images, generally speaking. No doubt a few people who know what they're doing do it, but I can't personally say I've ever seen an artist painted premult image with emissive colors, nor do I recall ever seeing a software rendered layer with emissive colors either. Is this common now? I've been out of film & games for a few years now. I'm already familiar with everything you referenced; and I can vouch that it's all very good stuff so thanks for sharing, especially the Adobe thread. I hope others here benefit. It's amusing that an entire industry knows who Chris Cox is because of this thread, right? :P

dahart 9y ago

> It is emissive. Yes you're right; I wasn't arguing with you about that. I always feel like calling it additive rather than emissive. But just because you can represent additive colors in premult images doesn't mean you should, and I'd speculate wildly that it occurs less often in production than halo problems. Someone who writes lens flare and rainbow shaders is going to scold me for saying that though... In the context of the OP's article, and of artists who paint images with transparency in them, worrying about emissive colors isn't really an issue. Artists very rarely paint pre-mult images, they can't work with premult images, generally speaking. No doubt a few people who know what they're doing do it, but I can't personally say I've ever seen an artist painted premult image with emissive colors, nor do I recall ever seeing a software rendered layer with emissive colors either. Is this common now? I've been out of film & games for a few years now. I'm already familiar with everything you referenced; and I can vouch that it's all very good stuff so thanks for sharing, especially the Adobe thread. I hope others here benefit. It's amusing that an entire industry knows who Chris Cox is because of this thread, right? :P