SketchUp Fireplace

[bubs]

Pibuz put in a little request a few days ago for a workflow tutorial on how I created the fire in the below scene. I am happy to oblige, so (for what it's worth) here goes!

The logs and grate were free models downloaded from 3D Warehouse with a bit of modification to remove sharp edges, put in my own materials etc.
https://3dwarehouse.sketchup.com/model. ... b05b21288d

Flames * EDIT * - PLEASE READ POSTS BELOW FOR A BETTER METHOD USING EMITTING NULL
I found an image of some flames on Google and then made corresponding clip and bump maps. I made an emitting material using the flames as a light source and then blended that with a null with the fire only at 5% visibility. I found this gave a good mix of light emitted whilst allow you the see through the flames a little. This material was applied to 4 planes throughout the logs as shown below.

Smoke
The smoke is just a .png image of smoke with a diffuse material, and again blended with a null this time with the smoke at 15% visibility. This material was applied to a simple plane in the middle of the logs.

Ashes
The ashes are a mix of 3 elements 1. some little pebbles 2. a displaced shape to look like a heap of small pebbles and 3. a displaced shape with the 'Fire Embers' material from the Mat DB applied.

Tweaks to improve realism
As there are not (as yet ) any emitting double sided thins for Skindigo we always run into the problem that the light emitted for the flame planes is only in the normal direction. In this case out towards the camera and to the right. In order to combat this I had to cheat a little to ensure I also get light emitting to the rear and the left. This was done by simply adding the flames material to areas of the logs as shown below. I can then just flip my grouped fire model along it's red or green axis to ensure these extra lights are not visible to the camera in any particular scene.
The last thing I did was to introduce a small amount of motion blur to the flames to give them that 'roaring up the chimney' look, this was done using Key Frames. I set the default position of the 4 flame planes as 0, moved them up 20mm and set this second position as 1.

And that, as they say, is that! Hope this help some people!

[Pibuz]

Wonderful! Thanks bubs!!! Very clear!

..I'd like to suggest you slightly change the topic name: there is a plugin for Maxwell called "Fire" which is sort of an integrated renderer, and this could be misleading for those who know ..maybe..."sketchup fireplace"?

[Zom-B]

Great tutorial but you missed two quite important things bubs!

1) The First is to use a nullMaterial emitter without any alpha map
2) your fire Mesh NEEDS quite some subdividing to render efficiently

The benefit of a nullMaterial is that it let pass light through and therefor causes no shadows,
also there is no need for a (bad) alpha map!

Here is an example with how much inefficient such a 1 quad mesh can be:

The basic Mesh, quite extreme here, since only a small part of the texture is emitting light:

Her a null emitter with this big poly mesh:

And here the same material with the polygons strongly subdived:

[Pibuz]

..all rendered for the same time I suppose.. Thank you Zom-B: always precious

I will investigate to understand the null emitter material, which is actually something I never ever thought of Thanks again!

[bubs]

@Zom-B - Thanks, I thought about that but you can't blend a null with a null, so my fire was always opaque, but I take your point that it's probably a more correct way to work... but this was just a tutorial on how I achieved what I did, and I am by no means saying this is the only (or correct for that matter) way to do this. Thanks for pointing out my bad Alpha by the way! This fire was never intended to be in close up, it's just a small corner of a larger scene, so I was happy that I was getting away with it!

[Zom-B]

@Zom-B - Thanks, I thought about that but you can't blend a null with a null, so my fire was always opaque, but I take your point that it's probably a more correct way to work...

Yes, the idea here is to have a nullMaterial with a emitting texture!

but this was just a tutorial on how I achieved what I did, and I am by no means saying this is the only (or correct for that matter) way to do this. Thanks for pointing out my bad Alpha by the way! This fire was never intended to be in close up, it's just a small corner of a larger scene, so I was happy that I was getting away with it!

I never aimed to blame you mate
The point here is simply since it is a tutorial, people will adapt this knowledge into different scenes and scenarios and maybe end up with some performance issue (=> noise) that the can't explain to them-self and maybe blame Indigo to be slow...
I simply try to avoid such pitfalls that end up with more problems and threads from new users

This is all stuff that actually belongs into some detailed performance FAQ, but at some point I stopped to beg Glare for such a thing...

..all rendered for the same time I suppose...

... check the information overlay for precise details

Thank you Zom-B: always precious

You are welcome as always!

[bubs]

I never aimed to blame you mate

No offence taken! I've a thicker skin than that! I've added a note to the OP to read down for the better method.

Always glad to learn new and better ways to do things!

[Pibuz]

Ok Zom-B: I'm trying to do the null emitter.
First of all, in SU we cannot choose null as a base shader, so I just exported a diffuse and I'm trying to set the material directly inside Indigo. What would be the correct workflow to get your nice image n.2?

[bubs]

Pibuz, mine works fine if I set the material type to diffuse, and in the emitter slot I checked 'texture', linked to my image and then set the layer and power as usual. When it exports to indigo I just select the material and change the type from diffuse to null, that's all.

[bubs]

Results using a null emitter on a subdivided plane for the fire as Zom-B suggests.

[Pibuz]

Pibuz, mine works fine if I set the material type to diffuse, and in the emitter slot I checked 'texture', linked to my image and then set the layer and power as usual.

Do you use a png..or a clip map maybe? I mean, to exclude the non-flames parts..

EDIT
Sorry for the question...it works...I thought I did the same thing yesterday but apparently I didn't..
Testing the subdivisions efficienty for a comparison now: it's not that I don't trust Zom-B: I just want to check if I got it right!

EDIT 2
Bubs: what did you put in the subdivisions slot for your flames' planes?

[bubs]

I set it to 8, but I didn't test anything else...

[OnoSendai]

A note about the subdivision of the emitting quad: you only need to do this when the emitting part of the quad is a small fraction of the overall quad (like in Zom-b's flame texture). For Bub's image, subdivision probably isn't needed.

[bubs]

I was convinced I couldn't see much difference during rendering with sub-div and not... thought I was going mad as there is clearly a big difference in Zom-B's test. This is good info to know!

[Pibuz]

Some tests.
The scene is exactly the same: same objects, same materials (null emitter), same light settings, same resolution. Only thing changing is the subdivision of the flames' mesh, as indicated in the images.

The best s/pixels and s/seconds rates are gained in the SUBD.10 test, although I think we get the cleanest result for subd.16.. what do you think?