Essential Blender- P24

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Switch to the "Particle Motion" panel. Figure PT.4: The Particle Motion panel. This panel tells particles how to move. Set the "Normal:" and "Random:" spinners both to "0.030" and press Alt-A to see the results. This time, the particles fly off the sphere, which is what you wanted. The reason you entered a value into the "Normal" control was that you wanted each particle to shoot off along the "normal" of the emitter object. The short description is simply that giving a velocity in the "Normal" control will cause particles to emit away from the surface of the object. A better description of normals is available in Chapter 4.
Figure PT.5: Particles flying off in the direction of the surface Normals. Particle Patterns You may have noticed in the animated playback that the particles seem to be flying off the sphere in a certain pattern. This is because Blender emits the particles from the object based on the order of faces and vertices within the object. When a primitive object like a sphere is created, the faces are ordered very neatly. In order to truly randomize the way that particles emit from a mesh, you must enter Edit Mode on the mesh (Tab-key), select all vertices (A-key), thenand then click the "Hash" button on the Mesh Tools panel of the Editing buttons (F9). The Hash function scrambles the order of vertices, meaning that particles will now seem to emit in a much more random fashion. What you would really like, though, is for your particles to fall down through the other obstacles in the scene. This is where the "Force" controls come in.
The upper bank of X/Y/Z force controls exerts a constant force on particles along the global axis of your choice. So, to make your particles "fall" as though they are affected by gravity, you need to assign a velocity along the global Z (vertical) axis. Set the "Z" force control to "-0.50," and preview with Alt-A. Figure PT.6: [no text] Note: If you find that your computer shows the animation slowly or sloppily, reduce the "Disp" on the Particles panel in order to show fewer particles. If things are running fine, and you have a fast enough machine, try setting the "Disp" value to 100, to show 100% of the particles. Barriers and Deflection RMB to select the rotated plane immediately below the emitter, then click the "Deflection" button on the "Fields and Deflection" panel to the left of the particle panels.
Figure PT.7: The Fields and Deflection panel. In this tutorial, you're only concerned about the upper section, labeled "Particles." By turning on Deflection, you tell the particle system to treat the object as a barrier. Pressing Alt-A now shows this, which is clearly wrong:
Figure PT.8: These particles are going crazy! The problem is that by default, particle paths are calculated at a fairly low resolution. You can adjust this with the "Keys" control of the particle motion panel. RMB to reselect the particle-emitting sphere, then set Keys to "50." What this value actually means is that along the total life of the particle (75 frames in your example), it will have its location calculated 50 different times. Before you changed the value, it had been set to 8, which meant that Blender was only calculating the particle position about once every ten frames. Obviously, 50 will be much more accurate. Alt-A again, and this time you will see that the particles bounce off the plane.
Figure PT.8.1: Particles properly deflecting from the top plane. Let's do one more thing with the deflection settings of the plane. RMB select the plane, then change the Deflection "Damping" setting to "0.8." Damping takes motion energy away from particles, slowing them down when they collide with the deflection object. Pressing Alt-A doesn't seem to show any difference. Annoying. Certain changes to the scene will not be detected or automatically taken into account by particle systems. When this happens, you have to tell the particles to recalculate manually. Fortunately, this is easy to do. To force a particle system to recalculate, RMB select the particle emitter, then click the "RecalcAll" button in the main Particles panel. Alt-A now shows the particles sliding off the end of the plane, as opposed to rebounding like they did before you changed the "Damping" value. There's one more thing to learn about Deflection. The deflection calculations are sensitive to which way mesh faces are pointing. Select one of the deflection planes and use the Tab key to go into Edit mode. In the "Mesh Tools 1" panel of the Editing buttons, enable the "Draw Normals" button and set the NSize value immediately above it to 1.0. You will see a light blue line
extending upward and away from the plane. This line indicates the Normal, or facing direction, of the plane's quad face. The deflection tools consider the Normal direction to be the "hard" side of the plane. If you were to rotate the plane 180 degrees and recalculate the particle system, you would see the particles no longer bouncing and sliding off the plane, but passing through it and slightly changing direction afterward. Be sure to keep surface Normals in mind if your objects are not deflecting correctly. Figure PT.9: The particles sliding off the damped plane. One at a time, select both the other plane and the open-topped cube, enable Deflection for them, and set their damping values to "0.8." When you're done doing that, don't forget to reselect the emitting sphere and manually recalculate the particle system. Preview the particle animation with Alt-A, and you will see your particles fall from the ball, deflect off each plane, then end up in the bottom of the cube.
Figure PT.10, 10.1: The particle system cruising along. Particles seem to be escaping from the bottom of the cube, and occasionally a particle may pass through one of the planes. The particle physics system is not a full, actual physics simulation and will be subject to little annoyances like this. Applying Other Environmental Forces Create an Empty and position it between the sphere and the first deflection plane. Use Alt-R to clear any rotations that might be on the Empty. With the new Empty selected, choose "Vortex" from the "Fields" drop down menu in the Fields and Deflection panel.
Figure PT.11: The Fields drop down with Vortex selected. Set the "Strength" field to "50," and play the animation. If you are in a front or side view, the effect might not be obvious, so use the MMB to rotate the 3D view a bit. Now, you can see that the particles, as they fall, are swirling in a cyclonic fashion. You can also see that the empty now has ghosted "vortex" lines.
Figure PT.12 Now that you've seen what Vortex can do, reduce its strength to 15 or so. That will cause the particles to follow the vortex force a bit, but to still stay pretty much within the confines of the rest of the scene. You can save this file for later reference if you like. After that, start a new Blender session with Ctrl-X for the next part of the tutorial. Strand Particles Blender's particle generator is not only capable of making standard particles as seen in the previous section, but also creates "Strands" that can be used to simulate hair, fur or even feathers. Let's start by adding a sphere from the Spacebar toolbox: Add -> Mesh -> UVsphere. You can accept the default creation values of 32. Put the sphere into Object mode with the Tab key.
In the buttons window, press F7 to bring up the Object buttons. Press F7 once more to cycle forward to the Physics buttons. Press the New button on the Particles tab, and you will again see the controls as they appear in the following illustration: Figure PTS.1: The default particles panel. Since you're about to create hair Strands, you need to make the particles static. Static particles are Blender's way of showing all of particles positions along its life at one time. The net effect is that a static particle looks like a long chain of particles that fill the path that a standard version of the particle would have followed. Press the "Static" button. To draw the Strands properly, you need to activate the "Vect" option. If you want the emitter mesh to show along with the particle Strands, press the "Mesh" button in the Display section. So where are the Strands? Like the previous example, strand particles need a velocity to be more than just points. Go to the Particle Motion tab and set Normal to 0.010. Your sphere and Strands should look something like the illustration, which is shown in solid view (Z-key).
Figure PTS.2, 2.1: An OpenGL and Rendered view of Strands. They look quite boring don't they? That's because they're just a bunch of Strands sticking out of a round ball. Let's make them look better! Right now, the rendered Strands stop abruptly and are the same size along their entire length. Real hair and fur tapers away to almost nothing, giving them their soft, whispy appearance. Let's take a look at how you use textures and materials to make to get the same effect with Strands. The Strand Shader Note: If you haven't already done Chapter 9: Materials and Texturing, the next part may go a bit too quickly for you. Although many parts of this book are independent, Strand rendering is quite dependent on proper materials and texturing. You are encouraged to work through Chapter 9 for a better understanding of this. Blender has a special shader for dealing with Strands. You'll use the Blend texture type along with the Strand shader to make rendered Strands appear to thin out toward their tips.
Figure PTS.3: Material buttons Map Input and Map To panels. The illustration above shows several panels of the Material buttons (F5). You will need to add a new material, and then add a texture to that material. Set the panels as shown. The "Strand" button on the Map Input panel activates Strand mapping and the Alpha button on Map To activates the opacity channel. Also, turn off the Col button (Color) in the Map To panel. Let's work on the "fading texture." You're going to set the texture in the first texture slot to a Blend. Check out the next illustration:
Figure PTS.4: The Texture buttons Texture and Blend panels. Note: We have torn off the Colors panel from behind the Textures tab where it began and adjusted the panel layout for clarity in the illustrations. Refer to Chapter 2 if you need help with this. Let's adjust the color and opacity of the Blend texture. On the Colors panel, press the Colorband button to show the Colorband controls. Set the "A" slider to 1.0 and pick a pure white from the color swatch right above it. Then, change the spinner that reads "Cur: 0" to 1. The Alpha and RGB sliders will change. Set A to 0.0 and pick a pure black from the color swatch. When you've done it correctly, it should look like this:
Figure PTS.5: The Texture buttons Colors and Preview panels. You've now finished the Blend texture that will create the fade effect on the Strands. Let's give your Strands a color by going to the Material buttons and selecting a color from the Col button's color picker on the Material panel. Also, to let the Alpha from the Blend texture take effect, turn the "A" (Alpha) slider on this same panel down to 0.0. In the Links and Pipeline panel, be sure to turn on ZTransp to allow the renderer to use transparency. To get a good preview of the effect all of this will have on your Strands, you can switch to the "Hair Strands" preview type in the Preview panel, and enable anti-aliasing by clicking the "O" button at the bottom.
Figure PTS.7: Preview, Material and Links and Pipeline panels. If you did everything as described above and press F12 to render, your render should look something like this:
Figure PTS.8: A render of the textured strands. You may have to adjust your camera angle and lamp position if you want to duplicate this exactly. It's a little hard to see in the book, but on your screen the difference between the old render and the new render will be obvious. You now have much softer hair Strands. There is one more thing you can do to give an even more tapered feel to the Strands before you start to add a lot more particles. Blender renders Strands with a width of one pixel, no matter how near or far they are from the camera. If you click on the "Strands" button in the Links and Pipeline panel, you can adjust the beginning and ending size of the Strands that the renderer uses. They can start out or end thicker or thinner, and you can even tell them whether to make the transition from thick to thin.
Figure PTS.9: The Strand palette. In this example, we've set the Start size of the Strand to 12.0 and changed the Shape to -0.900 so it's really "spiky." If you render now, here's how it looks:
Figure PTS.10 Now that you've done all the footwork, you're ready to have a lot of fun with hair and fur. Let's go back to the particle settings and create a lot more fur. In the Physics buttons (F7), turn the Emit amount up to 20,000. If you don't have a faster computer, you can change the Disp value to 20. All 20,000 particles will still show up at render time, but it will let you work much more quickly in the 3D view. Now that you have a lot more particle Strands, let's hit them with some gravity. Without being relativistic, gravity is just a downward force, so you change the Z value in the Force section of the Particle Motion tab to about -0.06. To make your fur a bit frizzy and random looking, set the Random value in the Velocity section to 0.015. To create an even better looking distribution of the particles, enable the Rand and Even buttons in the From section of the Particles tab. Note: If the fur Strands move in a direction other than downward when adjusting the Z force value, it could be that the emitter was created with a rotation. To remove this and see the Strands bend down with gravity, make sure the emitter is the active object and press Alt-R to remove any rotations.
Figure PTS.11: The Particles and Particle Motion tabs. If you render this, it will look something like the next illustration. The lighting setup that was used to render the images for this book is simply the default lamp switched to a spot lamp and tracked (Ctrl-T) to the particles. The spot uses a Classic-Halfway buffered shadow.