Creating a Cycles Fire and Smoke Shader

Currently (as of Blender 2.71) the Cycles Rendering Engine is lacking a default fire and smoke Shader when utilizing Volumetrics Rendering. As a result this post covers a simple setup to initialize a Shader that can control various, useful properties determining the look of rendered fire and smoke. This methodology is based on .

Properties of the Shader

• The Shader can logically be divided into a component that addresses Smoke and another addressing Fire, both of which are composited onto a single volumetric entity.
• At it’s simplest level both the Density of the Fire and Smoke can be controlled individually with a single value representing each respective component.
• The color of both components can be adjusted individually.
• Fire has the ability to illuminate surrounding elements within a scene, utilizing Cycle’s physically accurate renderer.

Scene Setup

Select the Default Cube go to

Object -> Quick Effects -> Quick Smoke

A Domain is created around the Cube, which subsequently becomes the Emitter object in the simulation.

Scale the Domain up to encompass a larger area, big enough to engulf the volume of the Fire and Smoke effect.

Select the Emitter.

In the Physics View under Flow Type choose Fire and Smoke.

Shader Setup

Playing through the animation at this point should render fire and smoke in the 3D View.

Switch to the Cycles Rendering Engine, usually located at the top of the screen in Blender’s Info View.

Select The Domain and in it’s Material Panel under Surface click the Use Nodes button.

Volume Shading

Blender would have created several default nodes (from the previous step) to render a default solid surface type. This is not applicable for volumetric rendering and subsequently needs to be adjusted.

With the Domain selected, in the Node Editor View delete the Diffuse BSDF Node.

Add 3 new Shader Nodes: Volume Absorption, Volume Scatter and Add.

Composite the two Volume Shaders within the Add Shader, which is subsequently output to the Volume Channel of the Material Output Node.

Switching the 3D View to Rendered, will reveal the effects of utilizing the Domain object’s Volume Channel for Material rendering.

Smoke Mapping

As you would have noticed the Domain renders as a volume but the Shader is currently still mapped to the original coordinates of the Cube object. In order to map the Shader to the Smoke and Fire Volume, add an Attribute Node (found under the Input Nodes Group) and set it’s Name field to “density”.

Connect the Nodes Output Factor (Fac) to both Volume Nodes’ Density Inputs.

Playing through the animation from the first frame will now render the Volume as expected.

Creating and Mapping Fire

As the fire will Emit light an Emission Shader Node will be used to simulate this effect.

Create another Add Shader Node and an Emission Shader Node.

Connect the Output of the Emission Shader Node to the Input of the new Add Shader Node. Disconnect the Output of the Add Shader Node created in Step 3 (to the Material Output Node) and Composite this Output within the remaining Channel of the Newly created Add Shader Node. Subsequently Connect the Output of the Newly created Add Shader Node to the Volume Channel of the Material Output Node.

This will revert the Domain to erroneous mapping. Creating the correct mapping for the Fire is a similar process to that previously covered with regards to Smoke.

Create another Attribute Node and enter “flame” in it’s Name input field. Connect this Nodes Factor Channel Output to the Emission Node’s Strength Input Channel.

Fire and Smoke can now be controlled as two separate entities within the same Shader.

 Color , Density and Intensity

Tweaking settings through the 3D View at this stage will be useful to determine an approximation of what the final rendering will look like as a quick preview. However, for best results use Blender’s Render option (F12 on the Keyboard by Default) to get an accurate representation of the final render.

Color

Control the color of the fire by adding a ColorRamp Node.

Connect the “flame” Attribute Node’s Color Output to the ColorRamp Node’s Fac input and connect the ColorRamp’s Color Output to the Emission Node’s Color Input.

The Smoke’s color can be controlled with a similar setup.

Intensity

Use a Gamma Node to control the intensity of the Fire, by intercepting the color throughput between the ColorRamp and the Emission Nodes.

Controlling Density

The Density of either the Fire or the Smoke can be controlled with a Brightness/Contrast Node by adjusting the Contrast value.

For the Smoke Connect the Fac Output of the “density” Attribute Node to the Color input channel of the Bright/Contrast Node.

Connect the Color output channel of the Bright/Contrast Node to the corresponding Density Outputs of the Volume Nodes.

 

 

 

 

 

 

Conclusion

Many more adjustments could be added to the Fire and Smoke to complement various rendering styles. This setup for a Fire and Smoke Shader in Cycles provides a basic component upon which many additional Nodes can be implemented, experimentation is the key in this case.

Download the file used in this post here

Creating Semi-Transparent, SSS, Veiny Wing-Skin

The Cycles Rendering Engine in Blender has many unique qualities that tend to set it apart from other Non-Realtime 3D Renderers such as the ability to visualize a Render within the 3D Viewport, an intuitive vitalization of a Material Node Network that also extends into Post-processing and a carefully considered balance between Biased and Non-biased rendering characteristics. However, what really seems to be most intriguing about Material/Shader set-ups in Cycles is probably one of it’s most communally underrated features, that being, it’s unique approach to isolating Surface Geometry for Shader set-ups.

Masks in Cycles serve the purpose of isolating parts of an image during Compositing or, as in the case of the image above, isolating parts of the geometry that make up a model’s surface.
If you have ever worked with Layer Masks in Photoshop or the GIMP, the concept might be easy to imagine. Nonetheless, the process of setting up a Mask in Cycles is so trivial that it warrants very little explanation. This could account for why the simplicity of this approach which disguises a full-featured arsenal of infinite, pixel-accurate, Shader combinations seems only to be reserved to passing asides in numerous online tutorials discussing Shader setups.

The above image depicts a typical set-up using masking with Cycles Nodes. Although this set-up results in a simple Shader that fades from one Diffuse Color to another, the simplicity and level of control necessitated when generating Shaders with Cycles for more complex Networks are principally similar.
For Example, the following image depicts how this masking technique can be used to isolate the veins on the Vampiro’s wings which require a different Shader to the rest of the wing.

In this case a Mask is used to balance a seemingly paradoxical requirement,

• In order to separate the Veins from the rest of the wing a different color is used to boost their presence.
• However, the deviation from the rest of the wing’s main color palette has the side-effect of causing the veins to look unintegrated in their default state.

As a result masking provides an ideal solution which allows for blending one Shader with another and controlling the effect with varying levels of grey, while maintaining modular editability within the Shading Network.

Although this mask might take some time to create, it’s application within the Shading Network allows a great deal of control over the final result and can be used in varying combinations within other sub-shader networks.
As mentioned earlier the simplicity of this masking technique seamlessly underlies the complexity of it’s ability to create a relationship between potentially unrelated physical properties such as Transparency and SSS (Sub-surface Scattering), Glossiness and NPR (Non-Photo-Realistic renders) to name a few of the infinite possibilities of Shading Network combinations. Subsequently it is worth bearing in mind that although the current Shading Network being discussed combines two SSS Shaders, blending Shaders of similar type is certainly not an inherent limitation of the technology, but used here simply as an approach to an aesthetic.
In this case the mask’s prominent white areas will boost the presence of the vein’s SSS Shader and the smaller veins (in varying scales of grey) serve the purpose of reintegrating the veins back into the SSS Shader consisting of the wing’s main color palette.

The above image depicts a single Texture node that is used for the Color input on both SSS Shaders, however the color is modified for the veins.
A Mask is then used to create a blend between the differentiating color palettes and physical properties of the two Shaders via a Mix Shader. This unique Shader, in itself, provides an output that can subsequently be used for combining the resultant Shader within other sub-shader networks.

In conclusion the benefit of this method, besides the simplicity in approach, is an editable Mask that both boosts and blends the offset color from and into the main texture colors. Furthermore, editing the color of the Veins through the RGB Curves Node does not require external software and as the process is internal there is no tedious reintegration required within the Shading Network.

Creating a Generic, Night-time Skin Shader

The obvious advantage of a Generic Shader is in the ability to re-use the Shader but still maintain applicable customization properties, such that a variety of effects can be achieved from a single Shader to simulate various natural phenomena.

The Node Editor in Blender provides an efficient interface for creating Material Shaders and Post-Processing Renders.
In this article I will addresses the techniques used to create a Skin Shader that can easily be transferred from one model to another, modified and retain consistency for properties related to the scene’s entirety.
The above image demonstrates a Generic Skin Shader applied to a character that will be rendered within a night-time scene. The same Skin Shader has been applied to the characters head and limbs, while masking (within the Material Node Network) provides the ability to customize unique properties on a per model/component basis.
This Generic Skin Shader consists of properties that make it unique to this image such as, a blue glow that will invariably prevail in most highlights due to the final output being a low light scene captured at night. Factors such as this make this Shader’s scope of usage limited when applied outside of Night-time renders, but factoring properties such as this into the development of this Shader will extend a consistent property across characters and ultimately serve the purpose of unifying the look of skin at night.
There are several main components of this Shader that should be editable as individual sets which consist of single or multi-Node groups. For example, the Normal Map Group consists of a single Image Texture Node as opposed to the Sub-Surface Scattering Group which consists of several SSS Nodes mixed with other Shader Nodes to produce the final result.
Relevant groups are listed below,

• Color Texture
• Normal Map
• Ambient Occlusion
• Glossiness
• Reflection
• Sub-Surface Scattering
• Masking

Material Node Editor for a Base Shader

Primarily, a Base Shader should remain simple but flexible.
The above image indicates how the Shader is easily broken up into smaller manageable groups that can be re-combined in ways that are applicable to the specific needs of the model. For example, the order that the groups are mixed into the Shader does not have to remain consistent as the Fresnel group used to simulate reflections can typically be mixed into the network towards the end for a less subtle effect as it occurs at night.

In this particular case simple yet prominent changes elicited within Groupings consisting of Texture Maps (at the beginning of the Network) will yield the most visible and relevant results. The creation of the Normal, Color and Ambient Occlusion Texture Maps per each model, as noted in previous posts, are reduced to Single Nodes within the depicted Node Network. With these maps in place, applying the Generic Skin Shader to another model is simply a case of duplicating the Shader and swapping out the applicable Maps (Color, Normal, AO) for that of the target model’s unique texture maps. The benefit of this method is in yielding a very quick setup for a Rendering that will produce an almost accurate simulation of the final result.

In Blender terms this is simply a case of selecting the target model you would like to transfer the Shader to, then selecting the Shader from the 1.  Browse Material to be Linked list and clicking the 2. Add Material button in the Material Properties View.

With the Base Shader copied to the new model/component replacing the applicable textures which in this case will be Color, Normal and AO can be achieved by opening the Node Editor View, locating the Texture Node and clicking the Single User Copy button in order to create a new data block that inherits the previous Node’s settings. Then browse to locate the applicable Texture file for the target model/component.
This simply ensures that the changes you make within this Node are not reflected in previously used Shaders.

Creating Normal Maps

High Frequency Detailing differentiates from High Resolution Sculpting as the process will generally require a completed Medium to High Resolution Sculpt in which the model’s topological structure can be retained. As High Resolution Sculpting is used to produce details that require geometric displacement (such as wrinkling and lower level detail), High Frequency Detailing serves the purpose of displacing light rays (such as with pores in a character’s skin) and therefore makes the effect more subtle as it will only be visible in sufficiently illuminated areas. Retaining a models topological structure while creating High Frequency Details, should also preserve the underlying High Resolution Sculpt detail and the model’s UV Layout.

The image above depicts High Frequency Detail (HFD) applied at a character’s skin level. Creating this level of detail has been achieved by sculpting with a modifier that retains the geometry loops that comprise the model’s topology, despite geometric subdivision. As the model’s High Resolution Sculpting should be completed at this stage, the purpose of using this modifier is multi-part as it will not only preserve details from High Resolution Sculpting (HRS) but also preserve UV layouts that were performed on the underlying geometry. It is therefore significant that geometry displacement deeper than wrinkling, is not targeted for High Frequency Detailing as this will potentially result in distortion of UV’s and HRS detail loss.

In the case of Blender, model topology preservation while sculpting can be achieved with a Multires Modifier.
Closer inspection of the detailing in the above image will reveal excessively boosted details in some areas (such as around the eyes and under the nose). It is important that details are boosted in these regions during High Frequency Detail Sculpting as much of the detail produced at this level is prone to becoming washed out either by a lack of sufficient illumination or Sub-Surface Scattering of light rays during render-time. Boosting details at this point increases the chances of their visibility in the final render, as a result it is therefore recommended that this technique is used sparingly in combination with the Mulitres and Normal Map method for HFD as noted below.

Multires in Conjunction with Normal Mapping for Rendering HFD

The creation of a set of custom made brushes for sculpting HFD should be determined by the requirements of the specific models. Nonetheless, there are certain brushes I’ve found to be consistent for many human-based characters such as skin pore brushes, cracked lip brushes etc. Below are several custom brushes used for sculpting this character’s High Frequency Details, you are free to download and use these brushes in your own projects permissible by CC0 (Creative Commons Zero) licensing.

Skin on Forehead and wrinkles around eyes (above) with finger skin (below).

Detail context (below)

When Sculpting of High Frequency Detail is completed a Normal Map can then be Baked from the result.

A Normal map should, however, not replace sculpted HFD but provide an additional level of control for HFD which is ultimately controlled with the Multires modifier in conjunction with the baked Normal Map.
When the Normal Map is applied to the appropriate texture channel (typically the Normal Map Channel) of the model’s material, and with the model’s modifier stack retaining the HFD in a Multires modifier, an additional level of control can be used to balance the model’s render times with details required for the final shot.
In other words using this method provides an additional degree of control over the model’s Level Of Detail (LOD), whereby mixing the results can decrease render times (by reduction of Multires subdivisions at render-time) for areas where this detailing does not prevail in the final render.
Use of the Multires modifier at this stage is also beneficial in terms of keeping viewport interactivity at realtime speeds as the modifier’s Preview setting can be set to 0.
Normal mapping can also render significantly faster than the excessively, sub-divided geometry required for HFD.

This set-up is particularly useful during animation when the same model is required for Wide to Extreme Close-up’s (ECU) but also useful when the effects of the Multires Modifier, Normal Mapping and High Resolution Sculpting are mixed for static imagery.

Retaining Quality and System Integrity

As the models in this image will be used for a still frame, the topology contributing to their appearance will not require deformation for the purposes of animation. As a result, reduction of the geometry (that determines the model’s topology) can be Decimated, as opposed to being retopologized, for Realtime Viewport interactivity during texturing.

The above image is a test render to depict the textures applied to certain models for a Color Pass. Ambient Occlusion, Transparency, Sub-Surface Scattering, Glossy and Material Properties have been excluded from this Pass. Working on an image such as this in multiple Passes will reduce system load, and keep Viewport interactivity as next to Realtime as possible.

Further improvements in reducing system overheads can be achieved by referencing High Resolution geometry externally.
This can be achieved by Decimating a duplicate of the model, then using a ShrinkWrap modifier to externally re-target a Subdivided version of the Decimated Model, to the original High Resolution model created from sculpting.

If we were to have a look at that statement more practically in Blender terms and propose it in the form of a question,

How Do We Get a High Resolution Static Model to Retain it’s Detail But still Provide Realtime Viewport Interactivity for Texturing?

1.Complete Sculpting and Save Separate Files

The above image depicts the Vampiro character’s top which is created by sculpting and has resulted in approximately 4 Million triangles.

Of course, many modern computers used for Sculpting can still handle a load of this type, but bear in mind, this is only one component of many that make up the Render as a whole. When the rest of the components are added to the scene interactivity in the Viewport (such as Panning, Dollying, Tumbling the camera etc) will drop to unusable and unstable levels.

It’s also worth noting that when this character is assembled the file size, as it is physically read by Ubuntu, equates to approximately 717MB.

The implication of working with a file this large is that it will consume physical disk space rapidly particularly as a result of incremental saving, slow down realtime interactivity by consuming system RAM (which is important when texturing as multiple applications need to be open simultaneously) and finally in severe cases could result in an unstable system reverting to Swap Space in order to compute simple user requests such as Panning, Dollying or Tumbling the 3D Viewport which only make up a small part of the texturing process and exclude cloning and painting amongst various other system intensive tasks.

If Sculpting is completed on the model at this stage. The model can be saved in a separate file, this is useful in terms of not increasing the file size any further but still being able to reference the high resolution model from another optimised file.

2.Duplicate, Decimate and Apply

The above image depicts a duplicate of the sculpted model that has been saved in another separate file. This model has then had it’s geometry reduced with the Decimate modifier, which has resulted in close to 99% reduction of polygons.

However this reduction has resulted in detail loss, particularly in areas where surface curvature appears smooth in the High Resolution model. Subsequently, Blender can compensate for this loss without reducing system performance by referencing the High Resolution model externally. This has the added benefit of not increasing the optimised, working file’s size by a factor of the High Resolution file’s size and thereby allowing for incremental saving of the working file with reasonable results.

3.Link Externally

From the file containing the Decimated model, the Decimate Modifier can then be Applied.
On a new layer, the High Resolution model can then be imported into the optimised file by using the Link command. This does not physically import the model into the current scene but adds a reference to it instead. A result of this operation is that, the High Resolution file cannot be moved from it’s current location (on disk) or the Link between the two files will be broken.

Saving this file with both High and Low Resolution models in a single unit will result in a much smaller file size.

4.Subdivide and ShrinkWrap for Render-time

With the High Resolution model referenced within the current scene, you will now be able to see the model in the Outliner and subsequently use this model as a Target for the Low Resolution model.

A Multires Modifier can then be added to the Low Resolution model in order to subdivide the model at Render-time and not during the Preview stage so as to retain Realtime Viewport interactivity. It has also been an observation of mine, that this method will reduce render times significantly.
Following the Multires modifier is the Shrinkwrap Modifier that is used to target the High Resolution model.

5. Conclusion

Subsequently there is no need to work on the High Resolution model further, and nor does Blender permit further object, or sub-object level editing of the Linked Model. Such edits should be performed on the original file and the changes will be reflected in the optimised file effectively.

The result of this preparation is that the Low Resolution model can then be UV unwrapped, Textured and Rendered with Realtime performance, a reasonable geometry count and used in combination with other models and components without reducing system stability.