BlenderArt Magazine » Modeling

Modeling A Robot Tutorial

Nam — Tue, 20 Oct 2009 23:18:34 +0000

This article deals with modeling a robot.

Part 1: Modeling the head
Part 2: Creating the eyepiece
Part 3: Creating the ear & mirroring the head
Part 4: Creating the upper & lower body
Part 5: Adding leftover details

Introduction. 3D modeling is one of the most interesting parts of the CG, but it provides quite a challenge for a beginner to the 3D modeling. In this tutorial we will take you through various techniques involved in modeling an simple looking robot in Blender. This particular robot if called ‘papero’ and its a companion bot produced by ‘NEC’ Corporation Japan.

Please note that this article is not made for any commercial gains and neither is allowed to be distributed or used for commercial gains. It is not affiliated to NEC in any way. The NEC robot referenced here is purely for educational purpose only.

The best approach to learn from this tutorial is also to consult the blender manual where ever you find it necessary especially if you are very new to blender then learn about the various naming conventions like view-port, ‘edit mode’, vertex, ‘transformer gizmo’ etc. In this tutorial care has been taken to provide these features as the heading of the steps, so that if we say add a cube you can reference on how to add an object step learned previously. Reading it once is recommended for every new users to 3D world of Blender even if you are not able to follow it properly.

Starting up First of all make a search on goggle for ‘papero’ or ‘NEC robots’ for reference images. Try to figure out how the model looks from different views. There are few different versions available but we are going to make a generic body. It would be helpful if you can get image1 from the net, if thats not possible it is also provided in the sample .blend file for this tutorial.

Image 1

PART 1
MODELING THE HEAD
Step 1. Adding a image to the view port: Start up Blender. First thing you need to do is delete the default cube. Right click on it to select it its not already then press [Del] and confirm deletion in the popup. Now we will add an reference image of the robot in the view port. Press [NumPad 1] for front view in the view-port, now go to ‘View |Background Image…’ menu of the view-port. In the popup click on the ‘folder’ icon and navigate to the reference image, select it and press Enter.

Step 2. Adding primitives : Now we will start modeling, we will first start with modeling the face. Keep the mouse in the view-port and press [Spacebar] In the popup menu go to Add |Mesh | UVsphere. Again in the new popup reduce the number of vertices to 24 and again 24 in another popup then press OK to add the sphere.

Image 2

Step 3. Working modes: Note that the sphere is added at the place where the insertion cursor(red white striped circle) is and the center of the circle is represented with a pink dot. Also you will notice that the object added is in ‘edit mode’. You can toggle the ‘edit mode’ to ‘object mode’ by pressing [Tab] key once. Do it now.

Image 3

Step 4. Moving Objects: Now to position the sphere in ‘object mode’ to the head part as seen in the reference image in back. to do that move your mouse over to blue arrowhead, click and keep pressed the button and move the mouse up wards. The sphere object will move upwards, keep press [Ctrl] Key to make big grid jumps. Use [Shift] in combination for minor grid jumps. Position the sphere as seen in the image.

Image 4

Step 5. Scaling Objects: To scale any object in ‘edit mode’ or ‘object mode’ you first have to select the object or its parts. Since the sphere is already selected. Press [S] key and any mouse movement towards the object center will result in scaling down of object and inversely any movement away from object center will result in scaling up of the size. Here scale up the size of sphere as shown in image following the reference in the back. Note again you can compliment the scaling operation with [Ctrl] or [Shift] or combination of both for better control.

Image 5

Step 6. Selecting vertices: Up to now you were working in ‘object mode’. Keep selected the sphere and press [Tab] to get into the ‘edit mode’. ‘Edit mode’ is the core of working on a 3D model, so learn and observe carefully. Now we will learn to select vertices. You can do various types of selection in blender. To select or deselect all vertices use [A] key to toggle. Press [A] till all vertices turn black(deselected). Now press [B] (box select) and move your mouse cursor to the top left part of the vertices in sphere click and drag down so as to select the left part as shown in the image.

Image 6

Step 7. Deleting vertices: Now we will delete the selected vertices. to do that press either [Del] or [X] key and in the pop select ‘vertices’. As now you can see the selected vertices are all gone. We did that because the robot head is symmetric in appearance so we need to just work on one half an later mirror it to get the complete head. Now as you can see in the image we have also selected the ear par of the same sphere. Yes we will delete them too. Do it the same way as explained just now.

Image 7

PART 2
CREATING THE EYE PIECE

Step 8. Zooming in the view-port: To zoom in the view-port you can use ’scroll wheel’ or [NumPad +] [NumPad -]. Now press [Z] key to toggle to shaded view mode from wire fame mode. Now as in the image select the two vertices by keeping pressed [Shift] key and right clicking on the individual vertices, select as shown in the image and then delete the two vertices to create the eye hole for the robot head.

Image 8

Step 9. Using Subsurface: Subsurface is the most important tool in 3d Mesh modeling. to enable Subsurface on the mesh press [F9] and in the mesh tab in the buttons window (below the view-port) Click the ‘SubSurf’ button also optimal button and increase the divisions to 2, see image.

Image 9

Step 10. Creating a face from vertices: Select the vertices as shown in the image10 and press [F] key once to make a face out of selected vertices. Now repeat it for other vertices on the hole as shown in the image11.

Image 10

Step 11. Subdividing an edge: Select the two vertices which are inside the hole for the robot eye. Press [W] Key and select ‘Subdivide’ , as soon as you select it the face gets divided into two faces. Image12. Repeat the steps with other newly created faces.

Image 11

Step 12. Merging faces: Triangular vertices faces are a bad for a smooth surface so we need to convert the two triangular faces to a single four vertices face. To do that select all four vertices of any of thee vertices faces. Watch image 12 for example. Now go to ‘Mesh |Faces |Convert triangles to quads’ in the view-port menu. And the triangular face gets converted into a four sided face.

Image 12

Step 13. Scaling the vertices: now select the vertices as shown in the image13 and scale them up a little bit so the shape of the eye hole looks like a circle. Here try to move the outer vertices of the eye in a straight line, use various methods of selection that you have learned earlier.

Image 13

Step 14. Extruding the faces: Get in to ‘Side view’ by pressing [NumPad 3] and select all the vertices of the eye that form a circle. Press [E] to extrude the selected vertices and start moving the extrusion in the direction of green axis of the transformer gizmo as seen in the image 14 (a) and (b).

Image 14

Step 15. Keep the last selection, now press [NumPad 1] to change back to the front view. Here once more press [E] to extrude and immediately press [S] to scale down the extrusion a little. See image 15.

Duplicating the vertices: To make a copy of the selected vertices/faces you can press [Shift +D]. Continued from the last selection press [Shift +D] and immediately press [P] (to separate it from the mesh into another object) click selected in the popup. Now you can press [Tab] to get out of the ‘edit mode’ to ‘object mode’. right click to select the new circular mesh and press [Tab] to enter ‘edit mode’ for it.

Image 15

Step 16. Now we need to create the tube like section for the eye. Select all the vertices [E] extrude them down a little (image 16a) Now get in to ’side view’ [NumPad 3] and extrude the selected vertices towards green axis twice as seen in the image 16b.

Image 16

Step 17. Welding the vertices: Welding or merging vertices gives us a closed face which we want for the back of the eye piece to be like. Now again press [E] and immediately ‘right click’ to leave the transform state. Now press [Alt + M] in the popup select ‘at cursor’ and you can see the duplicate vertices get removed and they all form a face as seen in image 17.

Loop selection: Now we need to create a eye cover glass for the eye piece. select the second loop of vertices from the eye piece. Press [Alt + B] and hover your mouse over the second circular loop in the image 18. The active selection will show a blue loop forming on it as soon as it does left click once to select the loop. Duplicate it and separate from this mesh. Get out of edit mode [Tab] now select the newly created mesh and press [Tab] to get into edit mode.

Image 17

Step 18. Following the image 20 extrude once and scale it down (image 20a) Then extrude it again , immediately right click. Then press [Alt +M] to join the vertices and complete the face for the eye cover glass. Get out of ‘edit mode’.

Image 18

PART 3
CREATING THE EAR & MIRRORING THE HEAD

You have noticed that many times we have duplicated a mesh part to start working on another part of the model. This is done for two reasons firstly the duplicated mesh we get fits closely to the par of the model where we picked it from and secondly it save a lot of time if we made that part from scratch like scaling moving and positioning it close enough. In the coming part we are going to deal with it even more

Step 19. Inner Ear: Again we will use duplicating method to make the ear piece. First select the head mesh get into ‘edit mode’ do one extrusion to very small distance towards red axis (image 19b) and duplicate it by [Shift +D]. Now get out of ‘edit mode’ and select the newly created mesh. Again get into ‘edit mode’ [Tab] and do three extrusion in red axis as seen in the image 19c.

Finally create one more extrusion and scale it down a little. Create a duplicate[ Shift +D] from current selection and separate [P] it from the mesh.

Image 19

Step 20. Outer ear part: Exit the edit mode and select the mesh just created. As seen in the image 20 extrude it three times and once more right click and weld the selected vertices [Alt +M].

Image 20

Step 21. Once again get out of the ‘edit mode’ and add a sphere of 16×16 ([Space Bar] ‘Add |Mesh |UVsphere’) in the middle of the ear as shown in the image 21. make sure that you position if right. Check the position in ‘front view’ and ’side view’ see Image 21.

Image 21

Step 22. Mirroring a mesh: Now the head is almost complete. Since the head is completely symmetric so we can go ahead and mirror it to get a completed head mesh. To do that select the ‘head mesh’ and make sure that you are in the ‘front view’ now press [Tab] to get into the ‘edit mode’. Press [A] key till all the vertices are selected. Noe press [Shift +D] to duplicate the selected mesh. Immediately right click to cancel any transformation. Not press [M] to bring up the mirror menu popup. here choose ‘X Global’. You will see the selected mesh is mirrored.

Image 22

Step 23. Merging the mirrored surfaces:. Now using the ‘transformer gizmo’ of the x axis (red) bring the two meshes closer so that the near edges are overlapping each other watch the image 23a for the highlighted part. At this point you can zoom in and make sure that those edges are ‘correctly overlapping each other. Now deselect all other vertices and make a box selection [B] around the highlighted part as seen in image 32a. Press F9 and go to the ‘Mesh tools’ buttons tab (image 24) and make sure the ‘limit value is 0.001′ and then click ‘Remove doubles’ button and you should get ‘Removed 24′ in the popup.

Now get out of the ‘edit mode’ and as soon as you get out of the edit mode you might see a black line in the middle of the head mesh as seen in image 23b. Again get in to ‘edit mode’ select all vertices and press [Ctrl + N] (calculate normals). Now the mesh will look smooth and you have created the head of the robot.

Image 23

Image 24

Step 24. Creating the res of the head parts. Now following the procedure of duplicating and mirroring go ahead and do the same for the ‘eye piece’ (image 25a) eye glass’ and the ‘ear ball’. After you have done that the final model should look some thing like in the image25b.

Image 25

PART 4
CREATING THE UPPER & LOWER BODY

Step 25. Make sure you are in ‘Object mode’. Got to ‘top view’ [NumPad 7} and add a UVsphere [Space bar] ‘Add |Mesh | Circle ‘ of 24 vertices (image 26). Get out of the ‘edit mode’ and change the view mode to ’side view’ [NumPad 3]. First position the circle just below the ‘ear part’.

Image 26

Step 26. Rotating the objects: Press [R] key to rotate the circle as shown in the image 27a. Get in to ‘edit mode’ and extrude once downwards on the Z axis (blue) and scale it as shown in the image 27b. Following the image extrude once more.

Image 27

Step 27. Extrude once more following the image 28a. Now we need to make out the body design as seen in the reference images. To do that get in to the ‘front view’ [NumPad 1] and box [B] select the vertices as shown in the image. [G] grab the vertices and immediately press [Z] and pull them down as shown in the image 28b and 29a.

Image 28

Step 28. Adding a loop of vertices: At this point we need to extrude vertices once and then scale them down so that we get a smooth bend edge for the body. But you will notice that the body looks a bit pulpy so we will add a new loop of vertices just near the bottom part (image 29b) to make it look like a solid surface with defined edges. To add a edge loop press [Ctrl + R] the cursor will now change in to a blue lop line and will follow the position of the mouse, bring it down and near to the bottom part as seen in image 29b and click to add the loop.

Image 29

Step 29. Lower body: Make a duplicate [Shift +D] of the same selection and separate it from the mesh. We will use it to make the lower body. Get out of the ‘edit mode’[Tab] and select the newly created mesh and again get into ‘edit mode’ [Tab]. Now extrude one and scale it a little. Again extrude and bring the extrusion down a little.
Extrude and bring it down as seen in image and here move the vertices in the same line. Now extrude twice following the image 30a and weld[Alt +M] the last extrusion.

Image 30

Step 30. Get in to the ’side view’ and scale the lower part of the ‘upper body’ and upper part of the ‘lower body’ as shown in image31a. Get out of ‘edit mode’ completely and add a plane [Add |Mesh |plane], position it near the side bottom of the robot body, watch image 31b for reference. press [F9] for editing buttons and enable ‘SubSurf’ button. The mesh will turn roundish.

Image 31

Step 31. Keep the view in ’side view’ [NumPad 3]Extrude the side of plane(two vertices) two times and move the vertices to look like as in the image 32.

Image 32

Step 32. Change the view to ‘front view’ [NumPad 1]. and extrude the plane three times outwards (red axis). and manipulate the vertices to as they look in the image33a image33b.

Image 33

Step 33. After the robot ’shoe’ has been done select all the vertices of the show and issue [Shift +D] move the selection to other side of the robot and after position it mirror [M] it in X axis. See image 34.

Image 34

PART 5
ADDING LEFTOVER DETAILS

Step 34. Changing the selection modes: The basic model is just about complete, we for got to add the little bump in the middle of head. Now select the head mesh and get into ‘edit mode’ Now we need to use the selection method as face as it will provide for easier selection. Press [Ctrl + Tab] and in the popup select the ‘face selection’ the view will change a bit as shown in the image. Now you can start selection the faces by right clicking on them, here you will need a group of faces to be selected so keep pressed the [Shift] key.

Image 35

Step 35. Extruding faces: Change the view to side. Extrude the faces upwards(blue axis) once. Now we need to rotate the selected faces only on x axis so we will press [R] and immediately press [X] and move mouse to rotate. Rotate the selected faces so that they look like as in the image.

Image 36

Step 36. Change view to front. Now change the selection mode[Ctrl +Tab] to vertices. And select the side vertices (three each side) as shown in image37a. Following the background image in the view-port move them down (z axis).

Image 37

See the outcome of it in the ’shaded’ [Z] mode.

Image 38

This wraps up the modeling tutorial. There are various smaller details left for the robot, they are left as an exercise for the reader. You can use use the methods provided here to create them, like the speakers in the front part of body and the tires of the robot. Make sure to read the other tutorial on texturing the robot in the learning section.

References & External Links

• .blend file

• Texturing A Robot

• Animating A Robot(Coming Soon)

Written by Gaurav Nawani, Graphic Artist at Ironcode Software

This article deals with the modeling a robot.

Part 1: Modeling the head
Part 2: Creating the eyepiece
Part 3: Creating the ear & mirroring the head
Part 4: Creating the upper & lower body
Part 5: Adding leftover details

Introduction. 3D modeling is one of the most interesting parts of the CG, but it provides quite a challenge for a beginner to the 3D modeling. In this tutorial we will take you through various techniques involved in modeling an simple looking robot in Blender. This particular robot if called ‘Papero’ and its a companion bot produced by ‘NEC’ Corporation Japan.

Starting up First of all make a search on goggle for ‘Papero’ or ‘NEC robots’ for reference images. Try to figure out how the model looks from different views. There are few different versions available but we are going to make a generic body. It would be helpful if you can get image1 from the net, if thats not possible it is also provided in the sample .blend file for this tutorial.

Image 1

Image 2

Image 3

Image 4

Image 5

Image 6

Image 7

PART 2
CREATING THE EYE PIECE

Image 8

Image 9

Image 10

Image 11

Image 12

Image 13

Image 14

Image 15

Image 16

Image 17

Image 18

PART 3
CREATING THE EAR & MIRRORING THE HEAD

Finally create one more extrusion and scale it down a little. Create a duplicate[ Shift +D] from current selection and separate [P] it from the mesh.

Image 19

Step 20. Outer ear part: Exit the edit mode and select the mesh just created. As seen in the image 20 extrude it three times and once more right click and weld the selected vertices [Alt +M].

Image 20

Image 21

Image 22

Image 23

Image 24

Image 25

PART 4
CREATING THE UPPER & LOWER BODY

Image 26

Image 27

Image 28

Image 29

Image 30

Image 31

Step 31. Keep the view in ’side view’ [NumPad 3]Extrude the side of plane(two vertices) two times and move the vertices to look like as in the image 32.

Image 32

Step 32. Change the view to ‘front view’ [NumPad 1]. and extrude the plane three times outwards (red axis). and manipulate the vertices to as they look in the image33a image33b.

Image 33

Image 34

PART 5
ADDING LEFTOVER DETAILS

Image 35

Image 36

Image 37

See the outcome of it in the ’shaded’ [Z] mode.

Image 38

References & External Links

• .blend file

• Texturing A Robot

• Animating A Robot

Written by Gaurav Nawani, Graphic Artist at Ironcode Software

Gears Tutorial

Nam — Tue, 18 Aug 2009 18:53:57 +0000

This article deals with the modeling and animation of gears, providing a short tutorial for the utilization of the Blender Mechanical Gears (BMG) script.

Introduction. One of the key points in modeling and animate mechanical devices relies in the need to produce gears. Gears are not merely “wheels with teeth”. Gears were like that in ancient days, but modern mechanics deeply studied the different ways in which spin can be transferred from one rotating axis to another, defining exactly how a gear must be designed for maximum efficiency.

Some theory can be obtained from the docs on [1] (I don’t want to promote any particular gear manufacturer, but this is the reference I used to create my gears) as well as in the Blender Mechanical Gears (BMG) script documentation [2]. Basically a gear must be designed so that no friction occurs at two meshing gear teeth. This ensures efficiency, long duration, and low noise. The mathematical description of a gear is based on the involute concept. The involute of a circle has several properties; the most important of which is that teeth of meshing gears whose profile is an involute do not slide one on the other while the gears rotate, and the pressure angle with which a gear pushes the other stay constant.

I will not go deeper on this here; you don’t need to know, since the BMG will handle mathematics, but if you are curious just browse [1,2].

The Script. BMG is a script suite you can download from [3]. It comprehends two scripts, a mesher (BMGm) and a spinner (BMGs) we will concentrate on the former first. BMGm belongs to the Mesh category if you elect to install it in the proper position within the .blender tree. In any case, once launched, it presents a screen as shown in Fig. 1

BMGm can create Cylindrical and Conical gears… the worm option is not working, yet . In this article we will concentrate on cylindrical to demonstrate script usage.

Figure 1. BMGm startup screen

Main Gear Parameters. This group of parameters defines the basic look of the gear. When two meshing gears are set what defines the geometry is the Pitch Radius, which is the radius of the ideal circle on which the meshing teeth of the two gears touch. It is the pitch radius the one defining most of the gear geometry. This, as most over entries, is defined in Blender Units. We will keep the default 5 for now. The teeth number defines how many teeth the gear has. This is the second most important parameter, and we will set this to 25 for this example. The Pressure angle is vital, from a mechanical point of view, but is of less importance in computer graphics. It defines the angle between the tangent plane to the gear tooth at the contact point and the plane containing the two gears rotation axis. It is probably better to leave this to the default 20° value. Helical Angle defines helical gears shape. Common gears have straight teeth. Helical gears have slanted teeth. Helical gear are less noisy and more swift in operation, and more costly to manufacture, all things you don’t care in 3D graphics, so we will keep this angle to 0 now. The Addendum and Dedendum defines how far beyond and beneath the pitch radius the teeth extends. These parameters are critical. First the Addendum cannot be greater than the dedendum, or you will have big meshing problems. Second, Their value must be tuned according to the number of teeth. The more the teeth, the smaller these two must be, the fewer the teeth, the larger they can be. For our example 25 is an average teeth number, so we can keep them to the default 0.4 value.

Beveling: No true mechanical devices have sharp edges. Fillet defines the radius of the rounding at the top and bottom of the tooth. Bevel defines the beveling of all edges on upper and lower face of the gear.

Mesh Parameters: The script generates a single tooth for the gear, with a given refinement level in the mesh. The refinement level is given as a Resolution along the tooth perimeter, which should be kept to 2 unless you are planning to zoom in a lot (rise it) or zoom out a lot (lower it) on your gears and a Longitudinal Resolution along the tooth thickness. This is actually needed only for helical gears, which do exhibit longitudinal twist. Finally the Thickness defines how thick is the gear and the Width defines how much to the inside, with respect to the pitch circle, the body of the gear extends beyond the tooth. Keep all these to their defaults

Pinion. There is no point in defining a gear without is matching pinion. The pinion can be either a standard pinion (a gear) a rack (a straight toothed item) a crown (a big gear with teeth on the inside) let’s keep the Pinion option and maintain the 12 teeth.

If now you press the Generate button you will see the scene in Fig. 2

Please note that the script generated a single tooth both for the main gear and the pinion. The main gear object center is in the origin, the pitch radius is 5 blender units, you can see this since the teeth would touch there, once rotated. The pinion radius has been automatically computed by the script, its center is in the right position for correct meshing (rightmost yellow dot) and the tooth has been produced slightly rotated for the sake of clarity.

Our next task will be to complete the gear and the pinion mesh.

Figure 2. BMGm result (top view)

Gear Meshes touch-ups. First of all, rotate the main gear tooth 1/50 of 360° (7.5°) (Fig. 3.1). This makes lower edge of the tooth aligned on the xz plane. In front view and edit mode we can extrude the top vertex to complete the profile (Fig. 3.2). Duplicating this and moving it around on the xz plane will make the profile for the inner gear part too (Fig. 3.3). Now duplicate all these new vertices and mirror them along global z with respect to cursor.

Figure 3. Profile completion

Now go back in top view with all these new vertices selected. Ideally we should spin (counterclockwise) three copies in a 14.4° angle. Sadly Blender does not accept decimals here! So we will spin them 15 copies along a 72° angle. (Fig. 4.1). Now Select the tooth, and SpinDup it by 5 times by 72°. You will have an extra copy of it (Fig. 4.2), which you should delete. Now remove doubles.

Figure 4. Some further steps…

Rotate the gear 36° clockwise, to have it symmetrically placed with respect to the xz plane. Now extrude some vertices from the inner part (Fig. 5.1 and 5.2) and extrude it towards the outer ring, merge some vertices where needed. It is also a good idea to use the Bevel script to make this arm nicer.

Figure 5. Almost finished!

Now you only have to SpinDup on 288° 4 copies and remove doubles! You might wish to scale the inner part a little along z only to make the gear less flat. Do something similar with the pinion too. But you won’t have the space to make the mesh so complex. Remember that the pinion has 12 teeth so a tooth is 30° (360°/12) wide. At the end you should have something like Fig. 6. Give to the Gear Object a mnemonic name (Like ‘Gear’) and to the pinion object a mnemonic name too (‘Pinion’ is a good choice!)

Figure 6. The two gears

Preparing for Spinning! To have the gears spin properly you will need to set up few things, but first, since two gears only is really a sad model, select both gears, duplicate them and move the copies so that the new Gear is coaxial and beneath the original pinion (Fig. 7). Give the duplicates smart names, like ‘GearB’ and ‘PinionB’. Be very careful, the Pinion and the GearB objects must have same x and y location, and an offset on z.

Figure 7. The four gears

Now add an empty for each gear, located in the gear center, with the z axis pointing in the direction of the gear rotational axis, then parent gears to empties. Give them matching names (Fig. 8).

Figure 8. The four gears parented to their proper empties

This is necessary because the spinning script (BMGs) will handle rotations for the gear as relative to the z axis. If the gears are to be moved and are not lying on the xy plane this will results in odd behavior.

By parenting gears to empties and by moving/rotating only the empties from now on – never the gears – the animation will behave properly.

Now launch the BMGs script. It is an ‘Animation’ class script. It will present quite an empty interface, with just an Add button. Press it four times and four lines will appear. In these line first column presents a Gear Object name. Fill ‘Gear’ in the first and ‘Pinion’ in the second, ‘GearB’ in the third, ‘PinionB’ in the fourth. Second column specifies the teeth number. ‘Gear’ and ‘GearB’ have 25, ‘Pinion’ and ‘PinionB’ have 12. This completes our gears database (Fig. 9.1). The gears database holds info on which objects in your scene is really a gear and should be spinned. You can Save and Load database to/from disk, the script generates XML files. You are advised to do so because the databases will be lost when you quit blender (The automatically generated script for spinning will not be lost!)

Now switch to the ‘Link’ Panel. Add three lines here with the Add button. The new lines appearing contain information on which gear is connected to which other. The first column in each line contains the driving gear, the second column the driven gear. The third column specify the link type, which can be a mesh kind of link, in which the pinion rotates in the opposite direction with respect to gear and the speed is given by the gear speed modified by the tooth number ratio. For coaxial gears, that is, for gears not meshing but rather mounted on the same axis the link type is fixed because the rotation speed is the same. In rare cases, with crowns and helical gears, the speed might still be in the tooth number ratio but not in the opposite direction. For these cases the InvMesh option exists.

In our example in the first line we will state that ‘Gear’ is the driver, ‘Pinion’ is the driven and the link is of ‘mesh’ type. On the second line ‘Pinion’ is now the driver, ‘GearB’ is the driven and the link type is ‘fixed’ since they are rigidly bound. At last, third line states that ‘GearB’ is the driver to ‘PinionB’ in a ‘mesh’ type link.

The Links database defines a consequential series of actions. If a driver gear is rotated its rotation propagates to its driven pinions and from these to their own driven gears and so on. To facilitate maintenance the two small buttons on the right allows changing links order.

Figure 9. Setting up gears and links databases

Once the links database is done (Fig 9.2) we are done. You should now press the Generate button. This creates a new script, named DriverSL (Fig. 10). This new script is stored in the .blend file and will not be lost when exiting Blender (You must have saved your file, of course).

Figure 10. Spinning script, automatically generated

To complete the set-up go to Script context in the Buttons Window and add a Scene Script link on FrameChanged event. Put DriverSL as linked script (Fig. 11)

Figure 11. Setting the Script Link

Let’s Go! Now we’re really there! First make a quick Frame 1 to Frame 2 and back switch. If some gears are not at 0 rotation they will revert to it (In this case our pinions) and you might have to rotate their empties (not the gears themselves!!) to recover a proper mutual meshing between gears.

Now select the driving gear, in our example ‘Gear’. And add to it a non-constant rotation IPO on RotZ (only on RotZ).

Now press ALT-A. The driver Gear will start to rotate, and the Pinion and all other gears will follow with a correct matching velocity!

Figure 12. Setting the IPO

References & External Links

• http://www.bostongear.com/pdf/gear_theory.pdf

Written by Stefano-Selleri

Plane-Line Intersection Tutorial

Nam — Mon, 07 May 2007 06:15:12 +0000

1.1. This article deals with the old Plane-line Intersection exercise that every student will find in his Descriptive Geometry practices. Well, everyone knows that the Plane-line Intersection is actually a point (Fig. 1). The process described in this article will help us to find that point: a) calculated with Blender modeling/editing tools; b) no scripts involved; c) with some geometric reasoning behind. The result therefore won’t be mathematically exact (we would need to do some maths and coding to achieve that) but quite an acceptable one, a very good approaching and backed by geometric logic.

Figure 1. The famous plane-line intersection.

1.2. The main purpose of exercises like that is to bypass current and unpredictable Blender Boolean tools. Once we are able to find that plane-line intersection, we can apply this process to a wide range of situations were we need to know which is the intersection between two objects of the scene. In the case below (Fig.2) I’ve calculated the intersection between the prisma and the plane, using the principles described in the paragraphs below.

Figure 2. An application of this practice.

1.3. The first exercise consists on finding the projection of an object (line) onto another (plane). We’ll find that by using consecutively side and front view in orthographic mode. Before starting, lets take a look on the Snap menu (Shift+S keys). On that menu, with the Cursor to Selection option we can place the cursor on a vertice previously selected. Then, if you put your pivot in cursor mode (Period Key), that vertice will be the pivot for scaling and rotating operations. Lets go. We start from a single object in edit mode. That object consist in a plane and a line that intersect one each other(Fig 3).

Figure 3. A plane and a line that intersect each other.

1.4. In a ortho side view (3 NumKey) , select an upper vertice of the plane as pivot. Then select the opposite vertice of that edge, duplicate it (Shift+D Key) and scale it (S key) until it coincides with the line. Do the same process with the lower vertices. (Fig.4). Select the two vertices we’ve created and join them by an edge (F key).

Figure 4. Projecting the line onto the plane.

1.5. Then we change to the orthographic front view (1 NumKey). We select a vertice from the resulting edge as pivot and scale the opposite one until it coincides with the line (Fig.5 i 6). The closer your are to the edges, the more precise the result. And that’s it. That point will be the plane-line intersection. You can check the result of the exercise by rotating the view (MMB).

Figure 5. Front view of the resulting line.

Figure 6. Scaling the line in the front view.

1.6. We can develop further this kind of geometric reasoning to solve more Descriptive Geometry exercises. In fact, if Blender can help us to solve this simple principle, then It could help us to solve any Descriptive Geometry exercise, even the most difficult ones. The next challenge will be the intersection between two planes (Fig.7). Is that possible?

Figure 7. Two planes that intersect one each other.

1.7. We start from a single object in edit mode. That object consist in two planes that intersect one each other (Fig. 7). Then, in a ortho side view (3 NumKey) we project the edges of a plane onto the other as described in paragraph 1.4 (Fig.8). The left vertice of the upper edge is the 1st. pivot for scaling vertices two times, one for the left edge and other for the right one. The same for the 2nd. pivot. We join the vertices we’ve calculated by edges.

Figure 8. Projections of plane edges onto the other.

1.8. As we see in the sequence below, when we change to the front view, we will probably need to change the vieport shading into solid mode to get a grasp of the situation. Then, scale your resultant lines according with what you see. When your lines have been scaled, join then and that will be the intersection between those planes. You can check your result by rotating the view.

1.9. That’s it. This time we’ve had a bit of fun with Blender by applying old principles of Descriptive Geometry, in fact a couple of hundred years old! A bunch of interesting links about Descriptive Geometry:

http://www.hindu.com/thehindu/2001/10/18/stories/08180007.htm

http://en.wikipedia.org/wiki/Descriptive_geometry

http://www.encyclopedia.com/html/d1/descript.asp

http://dg.vidivici.cz/dg/dge.html

http://geometria3d.250free.com/geomtr.htm

http://www.igpm.rwth-aachen.de/Download/reports/puetz/269.pdf