4x4 autodrive system 6 1

[3dpoder]

4x4 autodrive system
blend file for test.

Versión 6.1 -06/09/2009.

Mechanical setup, released under Creative Commons by 2.0 license. France. By Philippe roubal. 3d-synthesiscom.
features :
-All Terrain automated driving system, with automatic obstacles detection, not using physics simulation. The Game Engine is not used in this setup.

Just import your own model of car, whel and Terrain : the system is ready todo play.

Animating the car requires only todo edit the curve (trajectory) in top view, and adjust the speed of the vehicle by an unique ipo curve.

Driving character provided, automátically animated. You can easily edit the shape and materiales of the Mesh todo create you own character that Will still be animated if you dont break the vertex groups.

Automatic tracks creation After each whel. Generates animated textures for tracks in all Ground materiales : sand, mud, Soil, Snow, Grass.
warning : due todo several bugs in the particle system in Blender 2.49a and 2.49b, the tracks creator doesnt allow todo render the animated texture based on particles of object type. So, por favor, use Blender 2.48a. If you use Hair particles todo create tracks in Grass, 2.48a has a los a bug : Hair particles driven by an animated texture made of a sequence of images are not refreshed at frame change. So it is necessary todo use a small script written by atom, todo refresh the texture on the Ground Mesh supporting Hair (Grass) particles. The script is provided in the blend file..
*** please read carefully this manual ***.

special gracias and credits :
The speed rotation of each whel is calculated separately, according todo its displacement in the 3d world. This operación is done by a nice Python script kindly written by jérôme mahíeux (France), known as littleneoon blenderartists, org, released under copyleft license. Littleneo is the author of the famous script open city engine, generating amazing procedural cities. You can find this script on his website : http://Jerome, le, chat, free, fr.

I a los want todo thank atom, an other member of the same forum, who wrote a very small but very useful script allowing todo get rid of an annoying bug in the particle system, while waiting todo a real bugfix in a future Blender release.
layers :
-Layer 1 : main Rig :armature, sensors, empties.

Warning : the Bones of the armature are on two Bones layers. Only the Bones which are useful for the use of the system are shown by default (Bones on layer 1). The Bones layer 2, supports Bones essential for the Rig todo work, but that are not necessary in simple use situation.
make sure that all Bones are visible (Bones layer 1 and 2 enabled) when editing thearmature todo adjust the length of the vehicle according todo the process described below.

Layer 2 : curve, moving reference-meshes, empties.

Layer 3 : basic whels for testing purpose.

Layer 4 : Ground Mesh, used as reference by the 4 sensors, the curve and the square planessupporting empty-front, empty-rear, empty-stering-target, empty-head-target.

Layer 5 : template meshes for Bones custom shapes.

Layer 6 : car body model 1.

Layer 7 : car top (rof).

Layer 8 : car whels.

Layer 9 : suspensión arms.

Layer 10 : Blade springs (not used yet).

Layer 11 : grey background screen, particles emitters, and orthogonal Camera.

Layer 12 : particles objects : small Mesh used as tire print sample.

Layer 15 : driver-kit-sam. Automated driver and gear/clutch remote control box.
warning : this kit must stay on layer 15 : as some objects are set todo.

Unselectable, moving the kit todo an other layer Will not move the whole kit and Will break it. These unselectable objects are mostly parts of the remote control gear/clutch box.

The object driver-kit-parent has todo be parented todo the suspensión bone. The two empties empty-stering and empty-head have todo be parented todo the driver-kit-parent when you import them into an other blend file. To use them you Will have todo parent them todo empty-stering-target and empty-head-target.

If you want todo import this kit alone in an other file, do not forget todo unparent these empties and parent them todo the driver-kit-parent object before importing the kit.

Layer 16 : car body model 2.

Layer 19 : cameras.

Layer 20 : car body template and arrow Mesh.
note : all objects used in the car Rig are set todo not renderable.
caution. Script activation :
Pléase type Alt+p from frame one in the text window, todo activate the whelrotation, py script. This script drivers the rotation speed of the whels. As it is activated at frame 1, you Will have todo launch the animation from frame 1 at least 1 time, otherwize, your whels Will not rotate. Pléase read the script itself for more informacións about whels naming and setup.

Playing the animation :
Alt+a todo launch the animation.
sugestions :
1 -first, chek the setup with layers 1,2,3,5 enabled.
2 -chek the setup with layers 4,6,7,8,9 enabled.
3 -chek the setup with layers 4,6,8,9,15 enabled, and play with the gear/clutch remote control : look at the driver hands and fet. It is an animation tool, not a realtime tool.
4 -chek the setup with layers 1,2,3,11 enabled : type Alt+a from frame 1 todo se the tracks creator in action. The four particles emitters Will drop tires prints After each whel, while the tracks are baked in cache.
principle of the setup :
This is the 6.1 release, using armature and empties.

This Rig doesnt contain interdependencies, so it is more responsive than previous versións.

The car body is parented todo the blue custom bone named suspensión.

Bones are placed on 2 bone layers. You can disable the visibility of the bone layer 2 for normal use. Only the Bones used as parents for the whels Will be visible, as well as the axles and the suspensión bone. These Bones have custom shapes made from meshes used as templates and put on layer 5.

The principle of the Ground level and obstacles detection is based on four altitude sensors.

These sensors are grouped in two meshes named sensors-front and sensors-rear. Sensors-front follows the empty-front th rouge a copy location constraint and tracks the Empty rear. Sensors-rear is parented todo sensors-front.

These sensors are afected by Shrinkwrap modifiers : this means that the vértices of the square meshes are projected onto the surface of the Ground Mesh, along the z axis.

The vertex at the center of each square Mesh is used as a sensor todo detect the level of the Terrain. An Empty is vertex parented todo the central vertex of each square Mesh.

These 4 empties are used todo locate and align the Bones Alex-front-dn and Alex-rear-dn, in the 3d world, using copy location and track todo constraints.

As the geometry of the car chasis cant be kept by using a single Rig based upon these two axles, the informacións given by this basic Rig are reported onto copies of these axles, placed at the level of the whels centers. Axle-rear-up is locked on the z axis of the vehicle and copies the y rotation of Alex-rear-dn.

Empty-rear-ref-up is parented todo Alex-front-up and gives a precise location todo Alex-rear-up.

The choice of this double stage Rig allows todo get rid of geométrical Deformations of the chasis, but the drawbak is a very slight loss of accuracy in the contact between the whels and the Ground. However, it is noticeable only in extreme slopes, or when passing over a very big hole, and can be easily corrected manually if necessary. There are at least 3 methods todo do this correction. We Will se that later.

The sensors-front object is driven on the curve by the Empty front, th rouge a copy location constraint, and is pointing todo empty-rear, th rouge a track todo constraint.

The empties empty-front, empty-rear, and empty-stering-target, are vertex parented todo small square meshes all driven by the same dloc IPO, and following the curve gracias todo a curve modifier. An other square Mesh is added, named head-target. This Mesh supports an Empty named empty-head-target, used todo drive the behaviour of the automated driving character.

So, all the empties move on the curve with the same speed. This method is much more handy and accurate than using follow Path constraints.

The dloc ipo curve allows todo adjust the speed of the car. The front whels are parented todo the Bones named ster-front. R and ster-front. L. These Bones copies the direction of the ster-pointer bone. The ster-pointer object tracks the empty-stering-target. The influence of the track todo constraint, as well as the location of the stering-target square Mesh on the curve, can be adjusted, todo adjust the stering angle of the whels.

The rear whels are parented todo the Bones named Rim-rear. R and Rim-rear. L.

The behaviour of the rear whels on their trajectory can be adjusted by moving the square Mesh supporting the empty-rear along the curve, in the chosen direction, accordingly todo the ipo (dlocx or dlocy). Playing with the distance between the square Mesh rear and the center of the rear Alex, Will give more or less trail effect on the rear whels. No distance means that the rear whels Will pass exactly in the tracks of the front whels, and is not very realistic in narrow curves.

This said, reducing this distance on a small part of the trajectory is one of the methods todo correct the loss of altitude accuracy in extreme torsions of the chasis in high slopes. It is not the best method though.
.

[3dpoder]

importing your own Terrain Mesh


important : do not forget that several important objects are using the Ground Mesh, th rouge Shrinkwrap modifiers.

So, the Ground object name is important. To avoid troubles when importing the setup, give todo your own Terrain an other name, and import the Ground Mesh.

Then, select your Terrain and the Ground Mesh, and with the Ground Mesh selected, type Control + l and choose Mesh data.

The Ground Mesh Will kep its name, but Will get all its properties from your own Terrain Mesh. So, the new Ground Mesh Will be idéntical todo your own Terrain.

After that, you can deleete your own original Terrain Mesh. To be safe, always kep a copy of it in a file.
.

[3dpoder]

importing the setup into a personal Project

. The easiest and safest bien of using this setup is by importing your scene content into this file.

However, in Many cases, you Will probably prefer todo do the opposite. So here is the process:
1 -append the groups named car-setup and rear.
2 -select an object included in the car-setup group.
3 -select all the objects in the same group.
4 -scale all the selected objects up or do, todo match the width of your own car body model. I mean the distance between the right and left whels.
5 -when it is done, you have todo adjust the length of the rig, todo match the distance betwenthe front and rear whels a -select all the objects included in the rear group, these objects are the meshes named sensors-rear, and rear.


B -move the selected objects in the local y direction. Note the value of the displacement. The empties parented todo the meshes Will move as well.


C -select the armature. In Edit Mode, select all the Bones belonging todo the rear part of the armature, including the rear tips of the Alex-center-up and suspensión Bones.


De -move the Bones in the local y direction, todo match the distance between the front and rear whels. The displacement value is the same as the value noted in b.

When you exit the Edit Mode, the rear whels have followed the Bones, and are at the god place along the y axis, but they are not at the god altitude in z direction. Now we Will fix this:
E -in pose mode, select the bone named Alex-rear-dn.


F -in the constraints pannel, look at the limit distance constraint : click on the r button todo reset the distance limit. Now, the Alex-rear-dn bone is at the god location, and the rear whels should be at the god altitude.


G -still in pose mode, look at the armature in side view : you may notice that the bone named Alex-center-up is no more horizontal.


Select it and rotate it on its x local axis todo make it pointing at the Alex-rear-up bone. This time it should be horizontal, and the suspensión bone as well.

note : if the rear whels are not exactly at the same altitude as the front whels, it can be corrected by selecting the empties empty-r. L, and empty-r. R, and moving them slightly in the z direction.
8 -parent your car body model todo the bone named suspensión. This bone has a custom shape. It is the blue board with an arrow shape.
.

[3dpoder]

adding your own whels

. It is better todo add your whels After resizing the setup.
1 -select the bone named ster-front. R, and type shift+s. Chose cursor -> selection.
2 -select your whel model, and type shift+s. Chose selection -> cursor.
3 -parent your whel todo the bone named ster-front. R.
4 -repeat the same operación for the 3 other whels, parenting them todo Bones ster-front. L, Rim-rear. R and Rim-rear. L.
5-important : make sure that the rotation axis of your whels is the y axis. This condition is necessary for the script todo work. The y axis must a los be pointing todo the left, otherwize you whels would turn backward. The dimension of the whels on z axis is used as diameter by the whelrotation, py script todo calculate the rotation speed when the whel is moving in the 3d space.
.

[3dpoder]

altitude correction


There are 3 (at least) methods todo compensate altitude errors. As it acts directly on the whels, method 1 is the most eficient.
1 -the perfecto contact between the whels and the Ground level can be adjusted gracias todo the 4 empties parented todo the sensors. These empties empty-f. R, empty-f. L, empty-r. R, empty-r. L, are in a group named sensor-adjust.

You can adjust the altitude of the four whels in one time, by selecting the four empties, and moving them along the global z axis when the car Rig is on a flat horizontal Ground.

If you have todo adjust the whels level on a bumpy Terrain, in extreme estrés conditions, you can use the local z axis instead of the global z axis of the empties. In this case, you may have todo adjust each whel independently.
important : if you do such correction, it is important todo Insert at least 3 Loc keyframes : one before and one After the range of frames where the correction is neded. These keyframe are necessary todo isolate the correction área from the rest of the trajectory, todo avoid propagating the correction in áreas where they are not neded, and where the effect could be the opposite of the expected one.

Then, go todo the frame in between, in the location neding the máximum of correction. Move the concerned empties in z (local) direction, todo adjust the altitude of the whel, and Insert a third Loc keyframe.

Use the same method for each whel neding a correction.

In most cases, the Bézier interpolation of the ipo is suficient todo give the appropriate correction todo all the frames in the correction área. If not, just Insert some more keyframes or adjust the handles of the ipo Bézier curves.
2 -in most cases, whels altitude issues are due todo a shift of the sensors meshes, espescially in important transversal slopes and when the chasis (armature) is submited todo an extreme torsion.

A transversal shift of the sensors-rear Mesh can be compensated by hand by moving the sensors Mesh in its local direction by g+xx. Like in the previous method, it is necessary todo Insert a keyframe before and After the área where the trouble is visible, and todo apply the shift correction in the middle of this frame range.
3 -you can a los correct an altitude issue by constraining the rear whels todo pass in the same tracks as the front whels. As it is not realistic in narrow curves (when the altitude issues mainly occurs), it is not recomended. To do that, you have todo make the ipo of the rear Mesh a single user, and move this Mesh on the local y axis. The same precautions as previously must be taken : Insert a Loc y keyframe before and After the correction área, and apply the correction by other keyframes in between.

One more time : use this method with caution, and if you can avoid it. It is the worse of the 3 methods.
.

[3dpoder]

editing the trajectory


In top view, just edit the curve at Will. Remember that very narrow curves Will give less accuracy on the contact between the whels and the Ground.

The speed of the car and its starting point on the trajectory can be adjusted by playing with the dlocy ipo curve named speed on trajectory. This ipo is shared by the small square meshes following the curve.

The default dlocy ipo curve given in this example is set todo linear, but can be set todo Bézier todo get Smooth speed variations.
.

[3dpoder]

changing the initial direction of the curve


In this blend file, the initial direction of the curve use as guide for the trajectory is the y axis. You might want todo change that:
1 -select the curve and type shift+s. Chose cursor -> selection.
2 -select all the objects belonging todo the car-setup group.
3 -rotate the whole group around the curve center point, using the 3d cursor as rotation point.
4 -select one of the square meshes folowing the curve, and change the speed on trajectoryipo curve from dlocy todo dlocx.
5 -if you notice that the curve no longer passes by the center of the rig:
A -select the square Mesh named rear (the one supporting the empty-rear).

B -type shift+s and choose cursor -> selection c -select the curve and bring the curve origin on the 3d cursor : shift+s and selection -> cursor.
6 -if you have rescaled the scene, or at least the setup in the scene, you Will have todo edit theipo curve todo adjust the speed todo the new world.
.

[3dpoder]

adding obstacles on the trajectory

. There are at least 3 methods todo add obstacles on the Terrain:
1 -Making an obstacle in the same Mesh as the Terrain Mesh. These obstacles can be extruded from the Ground, or can be separated from it. In the second case, the Shrinkwrap modifiers Will have some dificulties todo detect the exact level of the obstacle because several layers of Mesh Faces Will give an average altitude detection. So, if it is posible, it is better todo deleete the vértices of the Ground below the obstacle.
2 -the Shrinkwrap modifiers can use two objects as referencias, so a second object can be used todo create obstacles.
3 -it is a los posible todo use an ordinary object as apparent obstacle. In this case, you Will have todo create an invisible obstacle (material with alpha) in an object detected by the Shrinkwrap modifier. This solution helps the whels todo Climb smoothly over the obstacle. It is very useful when the obstacle has Sharp Edges.
.

[3dpoder]

principle and use of the tracks creator

. The tracks creator is a característica allowing todo create tires prints (tracks) After the whels of your animated vehicle.

The setup can be used todo create animated textures of the tires tracks. Usually, these texturesare made of sequences of images.

Everything neded todo create the tires tracks is on layers 11 and 12.

Layer 11 : grey background screen, particles emitters, and orthogonal Camera.

Layer 12 : particles objects : small Mesh used as tire print sample.
note : you Will notice that there is an offset between the print sample and the particles emitters. This sems todo be a bug, and i have sen a report on the BugTracker page about that. So, if it is fixed in Blender 2.5 or in any future release, a small correction could be necessary in this setup.

The (*.jpg) format is well suited for this use. The texture that you Will render for your animated tires tracks Will have todo be detailed enough, but the compression factor is not an issue, because the tracks dont ned todo be very accurate, and you may Even ned todo blur them. The image of the texture Will be rendered with a high resolution. 2048x1536 is enough in most cases if the length/width ratio of your Terrain Mesh is 4/3.

As the image Will have todo be UV mapped on the Terrain Mesh, and a los used by a displacement modifier if you want the tracks todo be in real relief, the x and y dimensions of the rendered texture Will have todo perfectly match the size of the Terrain.

So, we Will use a Camera set todo orthogonal, todo capture the images of the animated tracks. This Camera Will be put right over the center of the Terrain Mesh (se layer 11), and Will be adjusted todo get the entire surface of the Terrain Mesh exactly inside the Bound of the Camera field.
When you Will have rendered the sequence of images in the wanted resolution, you Will have todo load the first image of the rendered sequence in the UV/Image Editor. Then, you Will select all Faces of the Terrain Mesh and type u with the cursor in the 3d window.

By selecting Project from view (Bound), you Will apply UV coordinates todo the Terrain Mesh. After that you Will have todo add the animated texture todo the Terrain material, and set the texture coordinates todo UV. Then, you Will be able todo use the animated texture with various parameters of your choice, in the map todo panel, as usually.

The animated texture Will a los be usable for a real displacement, by adding a displace modifier todo the Terrain Mesh. You Will use UV coordinates in the modifier as well.

Using a displace modifier allows very realistic tracks, but requires a highly subdivided Terrain Mesh. So it is very consuming in Ram memory, and the animation can be slowed down. Well se below that a turnaround can be used todo avoid crashes due todo high memory neds.
warning : if you have added some Grass on your Terrain by using Hair particles, you Will certainly want todo control the lenth of the Grass in the tires tracks todo simulate the Grass crushed by the car whels. At this point, you Will probably encounter some troubles, because of a bug in the particles system, not allowing todo refresh the texture at frame change. Dont worry : this setup includes a very small but eficient Python script written by atom, solving this problem while waiting for a real bug fix in a future Blender release. I have named his script grassparticlesdebug, py in this setup. To use it, the object on which the animated texture is applied must be selected. Obviously, this object Will be the Terrain Mesh (Ground). This script enter and exit Edit Mode for the selected object, forcing the particle system todo refresh and so todo use the new image in the sequence.

Atoms script todo fix the particles refresh bug:


Under the Terrain Mesh, we Will put a large plane with a material set todo a medium grey color (r=127, g=128, b=127). Rgb values of 128 can a los be used. This grey color is neutral when used with a Nor map parameter in the map todo panel. This allows todo add bumps and holes with the texture, by using darker or lighten value in the greyscale, between black and white. This large grey plane Will be used as a background grey screen.

The animated texture of the tires tracks Will be made by rendering tracks leaved by four particles emitters parented todo the rear Alex of the armature (the Alex-rear-up bone), and the two Bones named ster-front. R and ster-front. L.

These particles emitters are the simplest meshes ever built : they are made of one single vertex. Enable the axis and name in the 3d wiew, otherwise you Will have dificulties todo se and todo select them. As the emitters have no Faces, you Will set the emit from parameter todo vértices (vertex).


The particles emitters Will be put at the Ground level, and at the x and y location of the whels. Remarque that the front emitters are parented todo the Bones supporting the whels. Experiments have shown that in some animations better results have ben achieved with the tracks emitters only following the movement of the axles, and not rotating with the stering. So, it is up to you. If you are not satisfied by one method, fel free todo experiment the other bien.

The particles type of the particles systems Will be set todo objects. The particles Will be small meshes with materiales in greyscale color. These small meshes Will be used as samples, and Will represent a small part of the tires surface.

The provided print sample is made todo match the relief of the provided whel model. You Will be able todo edit the Little Mesh or todo create other prints sample todo match your own tires design.

The number of particles for each emitter Will be set todo the same number as the frames number in the animation. This way, at each frame, a single print sample Will be dropped by each particle emitter, just below the tires.

As we dont want the tracks todo vanish during the scene shot, the life of the particles must be set todo at least the duration of the animation. The baking range of the particles system must a los match the duration of the animation.

All the emitters Will share the same particles system, but if you create various print samples, you Will have todo select the sample object for each Emiter, because objets used as particles are linked todo the emitter itself, not the particle system.


To create the tracks, just select one of the four particles emitter and click on the bake button in the bake panel of the particle system. Make sure that the baking range matches the animation range.


During the process of creating the animated texture, the Terrain Mesh is not necessary. When baking the particles, the Terrain can Even be deleted. Deleting the Terrain Mesh doesnt affect the animation, because for the Shrinkwrap modifier, the Terrain is still kept in memory.

The positive thing is that deleting the Terrain Will free some memory somewhere (except for the Shrinkwrap modifier), and Will allow the baking process of particle todo avoid crashing. It is very usefull when the Terrain is large and highly subdivided, as it is generally the case when using a displace modifier.
warning : do not save the file with the Terrain deleted.

It is not necessary todo save the blend file After baking the particles, because the particles are saved in cache, anyway. Close the blend file and open it again, todo recover the Terrain Mesh.

When the particles are baked, you can render the animated texture. At this point, you must hide the Terrain Mesh. It mustnt be rendered, and Will be on a layer that Will not be selected when rendering. The goal is todo render with the orthogonal Camera only the prints samples over the neutral grey background.

On the image, you can se some gaps between the prints samples. It is mainly because of the perspective. As the texture is rendered in top view and with a Camera set todo orthogonal, these gaps are filled in the animated texture. However, some Little gaps can occur sometimes. If this happens and the gaps can be reduced by enlarging a bit the print sample Mesh in Edit Mode.

No lamps are necessary todo render the animated texture, because the materiales of the grey background screen and the materiales of the prints samples Will be set todo Shadeless.

If you want todo get smoother tires tracks, you can enable the do composite button, and adjust the values of the blur filter, in the compositing panel (screen 7), before rendering the sequence of images.
important : when you Will apply your animated texture todo a displacement modifier, you Will be able todo se the Terrain Mesh deformed in the 3d window. As the altitude sensors are following the Ground level, the real deformation of the Terrain Mesh is detected by the Shrinkwrap modifiers. This has an influence on the z location of the whels, and is mostly visible on the front whels. You can add a frame delay of + 1 or -1 frame on the image sequence of the tracks texture. Doing that, you move the first print sample After, before or right under the center point of the front whels. The visible effect is the adjustment of the z position of the front whels in the depth of the tracks.

You Will notice that the real relief of the displaced Ground Mesh introduces some vibrations in the whels. These vibrations can be adjusted by tweak the contrast of the animated texture, and can add realism todo the animation.

As i told you at the beginning of this manual, due todo several bugs in the particle system in Blender 2.49a and 2.49b, the tracks creator doesnt allow todo render the animated texture based on particles of object type. It sometimes work in simple files but doesnt sem todo work with the file of this setup. So, por favor, use Blender 2.48a.

Example of what can be done with both displacement modifier aplied todo the Ground Mesh and Grass made of Hair particles :
Last words:

I hope that this manual is understandable and that you Will find this setup useful. Fel free todo send me questions or comentarios at 3d@3d-synthesis.com. English is not my native language, so if you find typo, grammatical or spelling errors, por favor tell me as well.

If you use this setup, the provided models or the script in your animations, por favor dont forget us in the credits.wed be very happy todo se what you did with this system, so dont be shy and por favor send us alink todo your works.

Best regards, Philippe.
.