Explosion Test / Odd Render Result

Hello All,

I’m working on various effects for a stop motion animation. I’m using several different software suites but a vast majority of the effects Ill be creating will be in blender. Here is one such effect… I’m wanting a two tiered explosion effect. The effect looks right in the view port for the most part, however in the render I’m only rendering a partial effect. Only a portion of the smoke and fire is visible. I’m faily happy with the way the results look within the viewport and would like my render to better represent what is being displayed in the viewport. I’m no blender expert so there’s bound to be mistakes in what I’m doing. Also I’m having extremely long render times and I don’t even have the settings bumped up that high. Im not super tech savvy so I don’t know a ton about my system specs other than I have an i7 5820k cpu and an Nvidia GeForce GTX 980. Any advice would be much appreciated.

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Large Scale Smoke.blend (2.05 MB)

No one has experienced this result before? I suppose I’ll render a frame to better illustrate since this thread has a fair amount of views and no replies, I’m assuming most are just coming for the “Odd Render Result” in the title. It took around 3hrs + to render a frame the last time I rendered so I just continued working on other things so I wasnt bogging my computer down. I’ll post a screenshot of my view port and a Render for comparison sometime today.

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I don’t know what’s going on inside your smoke shader but I made a few adjustments that seem to improve the result. In the render settings->light paths, change volume to at least 1 so you have some volume sampling going on. In render settings-> geometry, change step size and/or max steps to higher values. Try .5 for step size and see if that helps (smaller step sizes require higher max-steps values to catch all the smoke) Higher steps size will decrease the volume resolution and increase render speed. Finally in your shader take smoke scale and smoke density down to about 0.25. I used a simpler shader to achieve this result on the GPU in about 10 minutes. GPU will help with render times also if you have a compatible one.


Here’s one using your shader with step size 1 and max steps 512. Smoke scale and density both 0.25 in the shader.


Thank you so much for your response. I was using a shader outlined by this tutorial for rendering smoke and flames in cycles. https://www.youtube.com/watch?v=oSiV5gg_lCs. I clearly must have misunderstood a few of the steps in constructing my Node setup. I’m still learning a lot about blender and consider myself to be a novice at best but I love the software so much and everything that it stands for in terms of being open source, especially when comparative software is so ridiculously priced. Anyway, I can’t tell you how much I appreciate your help, I was beginning to wonder if anyone was going to shed some light on this issue for me. I will immediately put your suggestions into use so I can do some more tests. I’d also like more control over the length of the fire burst. Is this done within the “fuel” parameters? I adjusted the settings but didn’t notice a marginal difference but perhaps I didn’t effect the settings drastically enough.

Also did you alter the vaules of the “flames” at all? The visual fidelity of your render seems well enough for my purposes being as that this explosion effect will be quite a ways away from the camera and likely obscured by other objects/buildings. And did you alter anything within the smoke physics (i.e. Divisions ect)?

If you’re worried about render time, I’ve gotten decent results using BI instead of Cycles. Depending on your render settings, it can render the whole thing in less than an hour.

I’m getting a lot of fireflies, not sure what the work around to this is. This frame was rendered at 512 samples with an Indirect Clamp set at 1. In the render below its not super obvious whats going on with the noise and the fireflies but when in motion its really quite rough. After I rendered a short animation it was immediately apparent that the fireflies were destroying the animation, it looked awful. So my question is, Is there something else I’m missing? I set the sampling to 1024 but there was still a bit of noise and it was wreaking havoc on my render times. This is the first I’ve messed with rendering smoke and fire and the like. I want my effects to be believable but not necessarily photo realistic. I’ve got a animation being rendered by render street so I will post my results when I get them finished. Thanks for all the help thus far!

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