C++: how do you update player height based on height of terrain? - c++

Question

I used to have a project that used a grey scale image to set the height of vertices in a simple flat mesh, which resulted in nice looking height mapped terrain. However, I have since converted my project to C++ and can no longer use the help of BufferedImage and such to use the old grey scale approach for creating height-mapped terrain from a flat mesh.
Because of this my C++ project now uses a .obj file for the terrain, but I am finding it very difficult to update the player/camera height as the user walks around the terrain, instead I just float through everything as the player height never changes or only does so very frequently (so I know the height is at least being updated, just not correctly).
Bellow is a small sample of code that does the actual updating of the player height based on the terrain.obj file, it does this by storing all the vertices of the .obj file and comparing each of their x and z components with the x and z components of the player and if there is a match then set the y value of the player to the current vertexes y position:
Vector3f *playerPos = freeMoveObjects[0]->GetParent()->GetTransform()->GetPos();
float playerXPos = playerPos->GetX();
float playerZPos = playerPos->GetZ();
int playerXPosInt = (int)playerXPos;
int playerZPosInt = (int)playerZPos;
for (Vector3f currentVector : meshObjects[0]->getMeshVertices()) {
int meshHeightXInt = (int)currentVector.GetX();
int meshHeightZInt = (int)currentVector.GetZ();
if (meshHeightXInt == playerXPosInt & meshHeightZInt == playerZPosInt){//currentVector.GetX() <= playerXPos & currentVector.GetZ() <= playerZPos) {
freeMoveObjects[0]->GetParent()->GetTransform()->GetPos()->SetY(currentVector.GetY());
}
}

Answer 1

What you're doing is very inefficient right now; you shouldn't have to loop through all vertices if you already have a heightmap which you can use for updating the player's position.
Why don't you store the heightmap in a pseudo-2d-array, like this:
class HeightMap {
private:
int width;
int height;
std::unique_ptr<int[]> data = std::make_unique<int[]>(width * height);
public:
HeightMap(int width, int height) : width{width}, height{height} {}
// you can default copy, move constructors and assignments
int heightAt(int x, int y) {
return heightmap[x + y * width];
}
}
Using heightAt you now have efficient random access to the data in the map. Thanks to unique_ptr you don't need to manage any memory manually and other constructors can be defaulted.
Note that you need to handle errors like x or y being out of range manually.