How to handle terrain holes?

[btduser]

Hi,

This will break collision detection in all cases, except when all surrounding neighbors of the hole (as well as the hole itself) have a height of 1. The reason is the terrain's collision geometry is built as quads, whose vertices' heights are read from the height map. So even if a quad if marked as a hole (its first sample having a negative height) we still need the actual height value for its neighbor quads to be correct, that's why we take the absolute value of the heights for building the quads after testing for holes:

Code:

if (h1 < 0) continue; // this would be a hole, skip quad
h1 = math.abs(h1);
h2 = math.abs(h2);
h3 = math.abs(h3);
h4 = math.abs(h4);

Let's say this happens on flat terrain, all samples having a height of 5. This quad's h1 (bottom left) sample is also its bottom left neighbor's top right sample. If h1 is -1 the current quad will be ignored, however the bottom left neighbor will have its top right corner incorrectly slanted down towards 1, yielding incorrect collision geometry around the hole. This is a crude diagram of the problem, "H" would be the current quad which is a hole, and "T" would be its bottom left neighbor which is solid terrain:

Code:

Incorrect:
       5-----5
       |  H  |   
5-----1-----5
|  T  |     
5-----5

Correct:
       5-----5
       |  H  |   
5-----5-----5
|  T  |     
5-----5

kind regards,

Got it, thanks for the explanation. So considering that the issue is really only when the height is exactly zero, would it be reasonable to do the following?

Code:

if (!isHole){
    value = height;
}
else{
    value = (height == 0) ? -1e-7f : -height);
}