.. _bpy.types.MaterialHalo: ************** Halo Rendering ************** .. figure:: /images/render_blender-render_materials_special-effects_halo_activate.png :width: 305px Activating halo rendering. Halo materials renders each of the objects points as glowing dots or a little clouds of light. Although they are not really lights because they do not cast light into the scene like a lamp. These are called *Halos* because you can see them, but they do not have any substance. Halos are rendered with vertex shaders and not with face shaders. This material is useful for simulating special effects, like particle effects or lens flares. Options ======= .. figure:: /images/render_blender-render_materials_special-effects_halo_panel.png :width: 305px Halo panels. To enable *Halos*, press the *Halo* button in the *Material* menu's top panel. As you will see in the 3D View, the mesh faces are no longer rendered. Instead just the vertex is rendered, since that is where each halo will originate. Halos can be hard to find in a crowded scene, so name it well for easy location in :doc:`the Outliner `. In the Properties editors, where we normally find the *Diffuse*, *Specular*, and *Shading* panels, we now see panels relative to the *Halo* characteristics: Halo Panel ---------- Alpha The transparency. Diffuse Color The color of the halo itself. Seed If non-zero, randomizes the ring dimension and line location. To use, give any (integer) number to start the random number generator. Size Sets the dimension of the halo. Hardness Sets the hardness of the halo. Similar to specular hardness. Add Determine how much the halo colors are 'added to', rather than mixed with, the colors of the objects behind and together with other halos. By increasing Add, the Halo will appear to light up objects that move behind it or through the Halo field. .. figure:: /images/render_blender-render_materials_special-effects_halo_add.jpg Effect of Add. Texture Gives halo a texture. By default, textures are applied to objects with Object coordinates and reflect on the halos by affecting their color, as a whole, on the basis of the color of the vertex originating the halo. Enable this feature to have the texture take effect *within* the halo, and hence to have it with varying colors or transparency; this will map the whole texture to *every* halo. This technique proves very useful when you want to create a realistic rain effect using particle systems, or similar. Vertex Normal Uses the vertex normal to specify the dimension of the halo. Extreme Alpha Boosts alpha. Shaded Lets halo receive light and shadows from external objects. When shaded is enabled, the Halo will be affected by local light; a lamp will make it brighter and affect its diffuse color and intensity. Soft Softens the edges of the halos at intersections with other geometry. In addition, several other special effects are available. To enable some or all of these effects, set the number of points/rings, or set the color of each effect individually: Rings Adds circular rings around to the halo. Lines Adds lines from the center of the halo. Star tips Gives the halo a star shape. You cannot use color ramps. Lines, Rings and an assortment of special effects are available with the relevant toggle buttons, which include Flare, Rings, Lines, Star, Texture, Extreme Alpha, and Shaded. *Halo variations* shows the result of applying a halo material to a single vertex mesh. .. figure:: /images/render_blender-render_materials_special-effects_halo_variations.jpg Halo variations. Flare Panel ----------- Enabling Flare Renders the halo as a lens flare. Size Sets the factor by which the flare is larger than the halo. Boost Gives the flare extra strength. Seed Specifies an offset in the flare seed table. Subflares Sets the number of subflares. Subsize Sets the dimensions of the subflares, dots, and circles. Lens Flares ^^^^^^^^^^^ Our eyes have been trained to believe that an image is real if it shows artifacts that result from the mechanical process of photography. *Motion blur*, *Depth of Field*, and *lens flares* are just three examples of these artifacts. The first two are discussed in the *chapter rendering*; the latter can be produced with special halos. A simulated lens flare tells the viewer that the image was created with a camera, which makes the viewer think that it is authentic. We create lens flares in Blender from a mesh object using first the *Halo* button and then the *Flare* options in the *Shaders* Panel of the material settings. Try turning on *Rings* and *Lines*, but keep the colors for these settings fairly subtle. Play with the *Subflares* number and Flare *Seed* settings until you arrive at something that is pleasing to the eye. You might need to play with *Boost:* for a stronger effect Fig. :ref:`fig-bi-material-halo-flare` settings. Note that this tool does not simulate the physics of photons traveling through a glass lens; it's just an eye candy. Blender's lens flare looks nice in motion, and disappears when another object occludes the flare mesh. .. _fig-bi-material-halo-flare: .. figure:: /images/render_blender-render_materials_special-effects_halo_lens-flare.jpg :width: 630px Lens flare. Halo Texturing ============== By default, textures are applied to objects with Object coordinates and reflects on the halos by affecting their color, as a whole, on the basis of the color of the vertex originating the halo. To have the texture take effect *within* the halo, and hence to have it with varying colors or transparency press the *Texture* button; this will map the whole texture to *every* halo. This technique proves very useful when you want to create a realistic rain effect using particle systems, or similar. Another Option is Shaded. When shaded is enabled, the Halo will be affect by local light; a lamp will make it brighter and affect its diffuse color and intensity. Examples ======== Dot Matrix Display ------------------ Let us use a halo material to create a dot matrix display: #. To begin, add a grid with the dimensions 32×16. Then add a camera and adjust your scene so that you have a nice view of the billboard. #. Use a 2D image program to create some red text on a black background, using a simple and bold font (you can just save the picture below on your hard drive...). :ref:`fig-bi-material-halo-matrix-texture` shows an image 512 pixels wide by 64 pixels high, with some black space at both sides. .. _fig-bi-material-halo-matrix-texture: .. figure:: /images/render_blender-render_materials_special-effects_halo_dotmatrix2.jpg Dot matrix image texture. - Add a material for the billboard, and set it to the type *Halo*. Set the *Halo Size* to 0.06 and when you render the scene you should see a grid of white spots. - Add a Texture, then change to the Texture Buttons and make it an image texture. When you load your picture and render again you should see some red tinted dots in the grid. - Return to the Material Buttons and adjust the *size X* parameter to about 0.5 then render again; the text should now be centered on the Billboard. - To remove the white dots, adjust the material color to a dark red and render. You should now have only red dots, but the billboard is still too dark. To fix this enter *Edit Mode* for the board and copy all vertices using the :kbd:`Shift-D` shortcut (take care not to move them!). Then adjust the brightness with the *Add* value in the Halo panel. .. _fig-bi-material-halo-dotmatrix: .. figure:: /images/render_blender-render_materials_special-effects_halo_dotmatrix.jpg Dot matrix display. You can now animate the texture to move over the billboard, using the *Offset X* value in the *Texture* tab of the Mapping panel. (You could use a higher resolution for the grid, but if you do you will have to adjust the size of the halos by shrinking them, or they will overlap. Fig. :ref:`fig-bi-material-halo-dotmatrix`). .. note:: Material Indices Halo materials only work when applied using the first material index. Any material(s) in a subsequent material index will not be rendered.