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manual/render/blender_render/materials/special_effects/volume.rst

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Volume rendering is a method for rendering light as it passes through participating media, Volume rendering is a method for rendering light as it passes through participating media,
within a 3d region. within a 3d region. The implementation in Blender a physically based model,
The implementation in Blender's sim-physics branch is a physically based model,
which represents the various interactions of light in a volume relatively realistically. which represents the various interactions of light in a volume relatively realistically.
.. figure:: /images/Volumerendering-solid_eq.jpg
Solid rendering
The process of rendering a solid surface involves the camera finding a piece of geometry,
then calculating the light that bounces from light sources (lamp objects, or other geometry),
off the surface, and towards the camera.
The light that arrives at the camera is the final color that's rendered.
.. figure:: /images/Volumerendering-volume_eq.jpg .. figure:: /images/Volumerendering-volume_eq.jpg
Volume rendering Volume rendering
Rendering a volume works differently. Light enters a 3D region of space (defined as the volume) that may be filled Rendering a volume is different then :doc:`Solid Render </render/blender_render/materials/properties/diffuse_shaders>`.
with small particles, such as smoke, mist or clouds. For volume light enters a 3D region of space (defined as the volume)
that may be filled with small particles, such as smoke, mist or clouds.
The light bounces around off the various molecules, being scattered or absorbed, The light bounces around off the various molecules, being scattered or absorbed,
until some light passes through the volume and reaches the camera. until some light passes through the volume and reaches the camera.
In order for that volume to be visible, the renderer must figure out how much material the In order for that volume to be visible, the renderer must figure out how much material the
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Options Options
******* =======
Density Density
======= -------
.. figure:: /images/Volumerendering-density.jpg .. figure:: /images/Volumerendering-density.jpg
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by controlling the density that one can get the typical 'volumetric' effects such as clouds or by controlling the density that one can get the typical 'volumetric' effects such as clouds or
thick smoke. thick smoke.
.. figure:: /images/Materials-VolumeRender-Options-Density.jpg
Density options
Density Density
The base density of the material - other density from textures is added on top The base density of the material - other density from textures is added on top
Density Scale Density Scale
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Shading Shading
======= -------
.. figure:: /images/Volumerendering-scattering1.jpg .. figure:: /images/Volumerendering-scattering1.jpg
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In real life different types of media can scatter light in different angular directions, In real life different types of media can scatter light in different angular directions,
known as Anisotropic scattering. known as Anisotropic scattering.
Back-scattering means that light is scattered more towards the incoming light direction, and Back-scattering means that light is scattered more towards the incoming light direction, and
forward-scattering means it's scattered along the same direction as the light is travelling. forward-scattering means it's scattered along the same direction as the light is traveling.
Asymmetry Asymmetry
Asymmetry controls the range between back-scattering (-1.0) and forward-scattering (1.0). Asymmetry controls the range between back-scattering (-1.0) and forward-scattering (1.0).
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Transparency Transparency
============ ============
.. figure:: /images/Materials-VolumeRender-Options-Transparency.jpg The transparency settings are the same as
:doc:`Solid Render </render/blender_render/materials/properties/diffuse_shaders>` except you have less settings.
For volume rendering you only have:
Transparency options - Mask
- Z Transparency
- Raytrace
Mask
Mask the Background.
Z Transparency
Use Alpha buffer for transparent faces.
Raytrace
Use Raytracing for Transparent Refraction rendering.
Integration Integration
=========== ===========
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Stop ray marching early if transmission drops below this luminance - Stop ray marching early if transmission drops below this luminance -
higher values give speedups in dense volumes at the expense of accuracy. higher values give speedups in dense volumes at the expense of accuracy.
Options Options
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Material uses this group exclusively. Lamps are excluded from other scene lighting. Material uses this group exclusively. Lamps are excluded from other scene lighting.
Examples Smoke and Fire
******** ==============
<these are sandbox edits to the whole shading intro section of the wiki, Create the Material
which groups materials and textures, and gives us an entree into Volumetric shading. -------------------
Note qualification of Mesh object. Need to investigate shading of other object types...>
Shading is the process and the code which enables an object to be seen in the final render The material must be a volumetric material with a Density of 0, and a high Density Scale.
output. Blender has four methods to shade a mesh object:
- Surface .. figure:: /images/material.jpg
- Volumetric :width: 300px
- Halo
- Wire
Surface shading indicates that the object is!a!tangible, The Material Settings
skinned!object that has a solid (but possibly pliable) surface, such as a chair, a sword,
or a peach. The surface is described in terms of having a diffuse, specular, mirror,
and transparency.
It may also have a semi-transparent surface and something inside of it that scatters light,
called sub-surface scattering. It may be reflective, such as chrome,!smooth plastic,
or metal, and may be partially transparent, such as!glass,!or liquid.
Volumetric shading treats the object as a volume of space that is filled with microscopic Smoke requires a complex material to render correctly. Select the big cube and go to the material tab.
particles, such as a cloud,!smoke, mist, fog, mystical spells, and steam. There change the material to 'Volume' and set the density to 0.
As light enters the volume, it is scattered by these particles, If you set the density to values bigger than 0 the domain cube will be filled with the volume material.
and some of that scattering reaches the eye/camera for us to see. The `other settings <http://wiki.blender.org/index.php/User:Broken/VolumeRenderingDev>`__ will affect the smoke,
The volume is described in terms of density, xxx. though. We'll cover those later.
The particles may be uniformly colored but have a varying!density within the volume,
and so the shape may have darker areas.
The density may be uniformly dispersed throughout the volume, or it may be clumpled,
giving a recognizable shape. Those microscopic particles may give off light themselves,
as if they contained!glowing embers or sparks,
or were transmitting some energy field inside the cloud.
That density may be driven by a particle system to create a well-defined jet or emission.
Halo shading turns each vertex of the object into a glob of light, an effect seen with sparks, Add the Texture
pixie dust, glint, and sparkles from, for example, a diamond in bright sunlight. ---------------
Halos can also be used to give a rough approximation of a lens flare, which is observed when a
real camera lens looks directly at a bright light source such as the sun.
Wire shading renders each edge of the object as a thin line, like!a wire cage, or net. In addition, Smoke requires its own texture,
Wire rendering is very fast and can be used as a proxy material for a more complicated surface you can use a volumetric texture known as :doc:`Voxel Data </render/blender_render/textures/types/volume/index>`.
to save time during intermediate renders. You must remember to set the domain object and change the influence.
There are two major components to shading: the Material and!its Textures. .. figure:: /images/rendering_bi_fire.jpg
The color that you see is a function of the light and the shading,
so you need to also check out the lighting section as well.
There are five types of objects in Blender that can be shaded: Mesh, Curve, Surface, Meta,
and Text.
The table below indicates which types of shading are available for each kind of object.
Keep in mind that all types of non-mesh objects can be converted from their type to a Mesh,
so, ultimately, all kinds of shading are available for all kinds of objects
The texture settings.
.. list-table:: Go to the texture tab and change the type to *Voxel Data*.
Shading available per Object type Under the Voxel Data-Settings set the domain object to our domain cube
(it should be listed just as 'Cube' since we are using Blender's default cube.
Under Influence check 'Density' and leave it at 1.000
(Emission should be automatically checked, too).
Now you should be able to render single frames. You can choose to color your smoke as well,
by turning *Emission Color* back on.
* - Surface .. figure:: /images/Smoke_render.jpg
- Halo
- Wire
- Volumetric
- no
* - Mesh
- yes
- full
- yes
- yes
* - Curve
- if cyclic or extruded
- no
- no
- no
* - Surface
- yes
- no
- yes
- no
* - Meta
- yes
- no
- no
- no
* - Text
- yes
- no
- no
- no
Finished Result
.. Comment: <!-- .. tip:: To see the smoke more clearly
[[File:1.png|300px|Step Size 1.0]]
[[File:8.png|300px|Step Size 0.5]]
[[File:3.png|300px|Step Size 0.3]]
[[File:4.png|300px|Step Size 0.1]]
[[File:5.png|300px|Step Size 0.05]]
[[File:6.png|300px|Step Size 0.02]]
--> .
Under the world tab, chose a very dark color for the horizon.
Extending the Smoke Simulator: Fire!
------------------------------------
You can also turn your smoke into fire with another texture! To make fire,
turn up the Emission Value in the Materials panel.
.. figure:: /images/e.jpg
:width: 300px
The Fire material.
Then, add another texture (Keep the old texture or the smoke won't show).
Give it a fiery color ramp- which colors based on the alpha,
and change the influence to emission and emission color. Change the blend to Multiply.
.. figure:: /images/f.jpg
:width: 300px
The fire texture settings.
.. figure:: /images/render3.jpg
:width: 640px
The fire render.
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