Getting Started - Chapter 4 - Avoiding a Car Crash

Avoiding a Car Crash

The simplest way of seeing if two meshes are in contact is to use the intersectsMesh method, as in


which will be true if a box bounding mesh1 would overlap with a box bounding mesh2. Each mesh has a built-in bounding box which lies close to the surface of the mesh that is used in checking the intersection of the meshes.

dudebox carbox

Since the character's walk and the car's journey are not phased together there will be a time when they are in the same place. However it is not possible to predict when the character, taking its long walk around the village, and the car, on its short journey, might intersect. In order to demonstrate the intersectsMesh method we will make the character walk backwards and forwards across the stopping place of the car.

In our case we want the character to stop moving if the car is in a "hit" zone and the character is not. It would, after all, be dangerous for the character to stop if they are both in the danger zone. In our case because of the way the Dude is constructed we need to use one of its children to check intersection. Basically Dude is just a holder node for the head, torso, legs and arms and the box bounding it is too small to be effective in this case..

Basic Collision Detection

Now make the hit box invisible.

Basic Collision Detection Invisible Box

This repeated animation looks a bit out off place. Even if we revert back to the character walking around the village the repetition of the car not only looks a bit silly it is also annoying. Let's improve the environment a little so that the car can appear to be driving through the village. We will place the village in a valley with distant hills created from a height map and put a road in for the car to travel along. While we are doing that let's add a sky and some distant trees.