[Research] Collision model for streets above the ground

[Andrés Fortier]

Try again to mimic the profile of the terrain and generate collisions for the roads.

[Agustin Alba Chicar]

I'll use some research made on issue #22 to begin with this task.

[Agustin Alba Chicar]

Here is a video of Nate Koenig explaining how to create a heightmap with a sample image.

[Agustin Alba Chicar]

Some updates:

As you can see the terrain is loaded through the sdf file, but we cannot get the right position of the height.

[Agustin Alba Chicar]

Got some results with terrains. The API is limited to integers for X-Y space, so this leads to floating point conversion errors as shown in the images below.

As for the record, the GetHeight(int x, int y) method receives the x and y positions in a memory matrix, so it is zero indexed and it is related to the space position using the following equations:

int x_mem = x_space + shape->GetSize().y / 2;
int y_mem = y_space + shape->GetSize().x / 2;

We should increase the height by shape->GetMinHeight() to get the absolute height.

[Agustin Alba Chicar]

@basicNew @JChoclin, I took another approach as a proof of concept of road collisions. I created a box which is static and it's floating, it is sent programatically but using a System Plugin instead of a World Plugin. I made a function to hardcode the height result given the x,y position in the map (similar to the terrain approach) and placed the road over the box. A picture is shown below.

I put two boxes to show that there area collisions and this is a perfect test case for a bridge. I'm not sure that creating boxes below the roads is the solution but creating something close to it yes.

[Andrés Fortier]

Nice! Question: Can we create a mesh with the same triangles as the road and use that for collision?

[Javier Iván Choclin]

No, we use markers for the roads, there is no equivalent for collisions.

[Agustin Alba Chicar]

@JChoclin, @andres_fortier Some new updates here. I have created a model with a polyline as its geometry. It has been extruded so as to have some height, but we can reduce it. Also, I have applied a collision to it, so we can hold things over it as the picture shows. I've made this just by creating a Gazebo Message and then publishing to the ~/factory topic. Points are arbitrary here, and I think we will improve code performance by not computing the triangles, just the road extents.

Here is a picture.

Hint: this is the same process as the buildings generated by the sdf generator, but with a pose whose position has a z value different from zero.

[Agustin Alba Chicar]

Just for the record, polylines are made from 2D points. This means that each change in the slope of the road will imply a new segment.

[Andrés Fortier]

+100

[Agustin Alba Chicar]

From the client meeting, we have decided to use the polylines with extrusion and get the heights from Manifold once it supports a format with that information built in.