Example of heightfield map?

[patrikpatrik]

Can you give an example of a heightfield map? I'm starting with a simple 64 x 64 black and white heightmap *.png file and my cube appears to be hitting something, but it's not lining up to the texture my heightmap is mapped to?

I'm using stbi library and use this to generate a heightmap terrain:

// terrain size & count
const int HEIGHTMAP = 64;
float heightmapArraySize[HEIGHTMAP][HEIGHTMAP]; // <-- for heightmap reactphytsics3d

// height map (for terrain generator)
	int heightX, heightY;
	unsigned char* heightMapData = stbi_load("./heightmap64.png", &heightX, &heightY, NULL, 1);
// storing into array
	for (int i = 0; i < HEIGHTMAP; i++)
	{
		for (int j = 0; j < HEIGHTMAP; j++)
		{
                        //heightmapArraySize[j][i] = heightMapData[HEIGHTMAP * j + i];
			heightmapArraySize[j][i] = getHeight(j, i, heightMapData, HEIGHTMAP);
		}
	}

I suppose my question would be, what values are supposed to be stored in the heightmapArraySize array, is it the actual heightmap int greyscale values from 0 - 256 or is it float type numbers? Here is the heightfield example:

// example of how to create heightFieldShape
	const int nbRows = 64;
	const int nbColumns = 64;
	float minHeight = -40; // <-- some value im not sure of, setting this min to 0.0f throws an assertion error @ 440 heightFieldShape.cpp
	float maxHeight =  40; // <-- some value im not sure of

	// create a heightfield map
	rp3d::Vector3 heightfieldMapPos(0.0f, 0.0f, 0.0f);
	rp3d::Quaternion heightfieldOrientation = rp3d::Quaternion::identity();
	rp3d::Transform heightfieldTransform(heightfieldMapPos, heightfieldOrientation);
	rp3d::RigidBody* heightfieldBody = world->createRigidBody(heightfieldTransform);
	heightfieldBody->setType(rp3d::BodyType::STATIC); // <-- set heightmap to static

	// Create the heightfield collision shape 
	// last param is done like rp3d::HeightFieldShape::HeightDataType::HEIGHT_INT_TYPE
	rp3d::HeightFieldShape* heightFieldShape = physicsCommon.createHeightFieldShape(nbColumns, nbRows, 
		minHeight, maxHeight, 
		heightmapArraySize, rp3d::HeightFieldShape::HeightDataType::HEIGHT_FLOAT_TYPE);
	// add collider
	rp3d::Collider* heightmapCollider;
	heightmapCollider = heightfieldBody->addCollider(heightFieldShape, rp3d::Transform::identity());

I'm not quite sure if I'm even doing this correctly, thank you!

[patrikpatrik]

Ugh... I always do this but I think I answered my own question. The array is wrong, should be:

// terrain size & count
const int HEIGHTMAP = 64;
float heightValues[HEIGHTMAP * HEIGHTMAP]; // <-- change here
// height map (for terrain generator)
	int heightX, heightY;
	unsigned char* heightMapData = stbi_load("./heightmap64.png", &heightX, &heightY, NULL, 1);
// storing into array
for (int i = 0; i < HEIGHTMAP; i++)
	{
		for (int j = 0; j < HEIGHTMAP; j++)
		{
			int arrayIndex = j * HEIGHTMAP + i;
			heightValues[arrayIndex] = getHeightFieldMapValues(i, j, heightMapData, HEIGHTMAP);
			if (i == 0 && j == 0)
			{
				minHeight = heightValues[arrayIndex];
				maxHeight = heightValues[arrayIndex];
			}
			if (heightValues[arrayIndex] < minHeight) {
				minHeight = heightValues[arrayIndex];
			}
			if (heightValues[arrayIndex] > maxHeight) {
				maxHeight = heightValues[arrayIndex];
			}
		}
	}

As per HeightField.cpp @ line 171. But most importantly, the terrain y position was always off by some factor. In the UserManual 11.1.6 HeightField Shapes, it states:
Therefore, if you create a HeightFieldShape with a minimum height of 100 and a maximum height of 500, the maximum coordinates of the shape on the Y axis will be 200 and the minimum coordinates will be -200.
In other words terrainPosition.y - (maxHeight + minHeight)/2 for the collider to line up with the terrain heightmap. And now I can change to different heightMaps *.png and objects falling correctly hit the terrain generated, at least for 64 x 64!👍