Create collision objects in ClearView RC sceneries

Introduction

ClearView uses photorealistic flying field created from real flying fields. To provide even better simulation, ClearView now provides real collision detection with objects from the scenery. This document describes how to add collision objects to an existing photo field.

Each scenery is represented with a directory under landscapes. In this directory, a file named landscape-params.txt defines some important settings for that scenery, like the initial model position, the weather parameters etc. There are some parameters that will be described here:

loadObjects

If loadObjects is 1, data/objects.ac will be loaded. This allows adding extra 3d to the photo scenery. This is used to add houses, trees, runways and helipads that do not exist in the actual photorealistic scenery.

textureMode

If set to 0, the texture does not assume the material attribute from objects.ac The objects appear flat. If set to 2, the texture is combined with the material attributes from objects.as the same way this is done when texturing models.

loadSkyBox

If loadSkyBox is 1, the photo realistic scenery is loaded. If 0 the scenery is not loaded. In that case you must set loadObjects 1 so at all 3d objects from data/objects.ac are loaded. This is used for pure 3d sceneries.

loadCtlObjects

If set to 1, all 3d objects from data/controls.ac will be loaded and used for collision detection. If set to 0, collision detection will be disabled. As a first step in creating collision detection for a scenery and empty controls.ac must be created with ac3d from ac3d.org and loadStlObjects must be set to 1.

The collision detection works when loadCtlObjects is set to 1. In that case, all objects from ctlobjects.ac are loaded and kept invisible. The model movement is tracked and any time the model body intersects with any of the collision objects the simulator will simulate crash of the model. That way the pilot can learn to keep away from different obstructions.

Creating collision file

The key into creating proper collision effects is creating of background collision objects that stay exactly where real artifact or objects are shown on the photo field.

Here are the steps that must be followed in creating collision object file controls.ac:

Enter “Collision Design” mode. To get into that mode, load any helicopter model and select “Advanced settings”. Change the value for specialMode parameter from 0 to 1 or 2 and save the settings. This will let you control the helicopter in special easy way so you explore the photo scenery and match the hidden collision objects to the current scenery. Use the sticks to move the model. Idle Up is used to reload and show the current collision objects and Throttle hold is used to set the coordinate display on/off. You must set the coordinate display off in order to use the menus.

For each object on the photo field, move the CM model to all corner vertices points of the object and write down the vertices coordinates.

Create the object in ac3d using the vertices coordinates obtained from the step above and save the result in controls.ac

Load controls.ac and check if the object is placed in the proper place

Switch IdleUp on/off to show on/off the newly created object and make sure it really lies right where the real object from the photo field is.

Move the model and observe if the collision is indicated when the model collides with the object.

Go to the next object and repeat the same process until done with all objects.

The model shape from the model 3d object is used for the collision computations. To have different shape (or include the main rotor) create file colbody.ac with the proper model shape that will be tested for collision. It is desirable, instead the model shape from the model ac file, to create simpler shape in colbody.ac file. This will increase the performance.

Collision design mode commands

ClearView is placed in collision by going into Collision design mode. To get into that mode, load any helicopter model and select “Advanced settings”. Change the value for specialMode parameter from 0 to 1 or 2 and save the settings. To exit from that mode, change the specialMode settings back to 0 or load any other model.

UdleUp – When on, loads and shows the current content of controls.ac. When off, clears all controls.ac objects from the screen.

ThrottleHold – When on, shows a message with collision indicator, exact model coordinates and distance. If set on, the menus are inaccessible. Set the switch to off to clear the message and makes all menus accessible again.

Throttle stick – moves CM model up and down around the Y axis.

Elevator stick – moves CM forward and back along the Z axis.

Aileron stick – moves CM model forward and back along the X axis.

Following is step by step instruction for collision enabling FarmField

FarmField contains a fence on the right side of the model start area. I will document step by step how to add collision for that fence. Adding more collision objects is basically repeating that same process again.

First, I entered into collision design mode as described above. I use my own helicopter model that is represented by football ball and a donut but you can use any helicopter you like, just change specialMode parameter to 1 or 2 (for two different stick modes of movement).

I expanded the file under model directory and started ClearView. I loaded FarmField and then loaded CoordSelector model. The program changed into collision design mode:

Note the message bar at the bottom. You can toggle it on and off via Throttle Hold switch. Note that when the bar is on, you can’t select the menus, so switch it off when need to select something from there.

The center of the red ball is the current model coordinates. The center of the black dot at the shade is the vertical projection of that coordinate on the ground (X,Z). You can move the model with the sticks and write down any coordinates that you may need to create the collision objects.

Now, I am going to take the coordinates of the net so I can create a proper collision object for it. Let’s move the model to the first point I want to take:

I want to take the coordinate at the base of the net. I lifted the model and position it so the shade gets exactly at the base of the net. Now I am ready to lower the model exactly at the desired place:

Now the center of the model is positioned exactly at the point that is the base of the net. Now I can write down that point coordinates as shown on the message bar:

Net base point: (-0.01,-0.23,-10.62)

Now I move the model up and little to the left at the top net point:

Net top point: (-0.09,3.74,-10.58)

Not I want to get the net bottom point at the end of the net far at distance:

Net base point back: (2.48,0.57,-82.74) Moving the model up I get the net base point top:

(2.39,6.26,-82.74)

I ended up with four points:

Net base point: (-0.01,-0.23,-10.62)

Net top point: (-0.09,3.74,-10.58)

Net base point back: (2.48,0.57,-82.74)

Net top point back (2.39,6.26,-82.74)

Here is the four point surface I defined:

Now let’s fire ac3d . Create a rectangle and then drag each of its vertices to exact coordinates that we extracted for the net in the step above. Then apply a material and set the transparency to 50%. Then save the file as controls.ac in data sub directory of the Farm Field. Here is a screen from ac3d:

Keep ac3d open. Now we will load this in ClearView and see how well this covers the mesh. If needed, the object can be moved in ac3d and saved. On ClearView, by flipping the Idle Up switch the new changes will be loaded so we try again for match. That process can continue for some iteration for more complex models.

Here we see the collision object and the net. Flip few times the Idle Up switch. This hides the collision object and reloads all collision objects from controls.ac We see that the top of the object does not align with the top of the net. Let’s move the top vertex in ac3d, save in ac3d and reload flipping the idle up switch.

Here is the finished image from ClearView with the collision object shown over the net:

We can repeat the same process for the car or any other objects that we may want to make collidable.

To verify that the collision object for the new is working, load any model and try to hit the net.