HeightMapSampler.cpp

#include "HeightMapSampler.h"
#include "lodepng/lodepng.h"
// this function sets the region to sample from.
void SF_Heightmap::setSpecs(const ivec3& from, const ivec3& to){
	minBound = from;
	maxBound = to;
}
void SF_Heightmap::loadPNG(const ivec2& _dim, const char* fileName){
	dimension = _dim;
	std::vector<unsigned char> pngData; //the raw pixels
	unsigned int width = dimension.x;
	unsigned int height = dimension.y;

	lodepng::load_file(pngData, fileName);
	unsigned int error = lodepng::decode(image, width, height, pngData);
	assert(error == 0);
	imageBuffer = image.data();
}
unsigned char SF_Heightmap::materialFunc(const ivec3& pos, const int cellSize, vec3* intersects, vec3* outNormal0, vec3* outNormal1, vec3* outNormal2){
	vec3 floatPos(pos);
	ivec2 i2pos(ivec2(pos.x, pos.z));
	ivec2 i2posXEnd(ivec2(pos.x + 1, pos.z));
	ivec2 i2posYEnd(ivec2(pos.x, pos.z + 1));
	//floatPos *= sampleScale;
	unsigned char material = 0;

	float heightOrigin = getHeightSimple(i2pos);
	if (floatPos.y <= heightOrigin){
		material = 1;
	}
	if (floatPos.y <= heightOrigin && floatPos.y + sampleScale >= heightOrigin){
		// crossing on the y axis.
		intersects->y = (heightOrigin - floatPos.y) / sampleScale;
		// calculate normal
		*outNormal1 = getNormal2(vec2(floatPos.x, floatPos.z), heightOrigin);
	}
	//float intersectionHeight;
	float heightXEnd = getHeightSimple(i2posXEnd);
	vec3 normal = getNormal(vec2(floatPos.x, floatPos.z), heightOrigin);
	if (floatPos.y > heightOrigin && floatPos.y <= heightXEnd){
		// on an incline on the x axis.
		intersects->x = (floatPos.y - heightOrigin) * sampleScale / ((floatPos.y - heightOrigin) + (heightXEnd - floatPos.y));
		//intersectionHeight = getHeight(vec2(floatPos.x + intersects->x, floatPos.z));
		//*outNormal0 = getNormal(vec2(floatPos.x + intersects->x, floatPos.z), intersectionHeight);
		*outNormal0 = normal;
	}
	else if (floatPos.y <= heightOrigin && floatPos.y > heightXEnd){
		// on a decline on the x axis.
		intersects->x = (floatPos.y - heightOrigin) * sampleScale / ((floatPos.y - heightOrigin) + (heightXEnd - floatPos.y));
		//intersectionHeight = getHeight(vec2(floatPos.x + intersects->x, floatPos.z));
		//*outNormal0 = getNormal(vec2(floatPos.x + intersects->x, floatPos.z), intersectionHeight);
		*outNormal0 = normal;
	}

	float heightZEnd = getHeightSimple(i2posYEnd);
	if (floatPos.y > heightOrigin && floatPos.y < heightZEnd){
		// on an incline on the z axis.
		intersects->z = (floatPos.y - heightOrigin) * sampleScale / ((floatPos.y - heightOrigin) + (heightZEnd - floatPos.y));
		//intersectionHeight = getHeight(vec2(floatPos.x, floatPos.z + intersects->z));
		//*outNormal2 = getNormal(vec2(floatPos.x, floatPos.z + intersects->z), intersectionHeight);
		*outNormal2 = normal;
	}
	else if (floatPos.y < heightOrigin && floatPos.y > heightZEnd){
		// on a decline on the z axis.
		
		intersects->z = (floatPos.y - heightOrigin) * sampleScale / ((floatPos.y - heightOrigin) + (heightZEnd - floatPos.y));
		//intersectionHeight = getHeight(vec2(floatPos.x, floatPos.z + intersects->z));
		//*outNormal2 = getNormal(vec2(floatPos.x, floatPos.z + intersects->z), intersectionHeight);
		*outNormal2 = normal;
	}
	return material;
}
float SF_Heightmap::getHeight(vec2 pos){
	ivec2 floorPos = glm::floor(pos);
	vec2 remainderPos = pos - vec2(floorPos);
	
	float val0 = getRGBSum(floorPos);
	float val1 = getRGBSum(floorPos + ivec2(1, 0));
	float val2 = getRGBSum(floorPos + ivec2(0, 1));
	float val3 = getRGBSum(floorPos + ivec2(1, 1));

	// use a simple sampling method for four-point sampling.
	float bottom = val0 + remainderPos.x * (val1 - val0);
	float top = val2 + remainderPos.x * (val3 - val2);
	float height = bottom + remainderPos.y * (top - bottom);
	return height;

}
float SF_Heightmap::getHeightSimple(const ivec2& pos){
	float ret = getRGBSum(pos);
	return ret;

}
vec3 SF_Heightmap::getNormal(vec2 pos, float height){
	/* use this simple method to calculate the normal.
	   sample the heights of the four adjacent points. if it's at the boundary,
	   arbitrarily set the normal to pointing upwards, for now.
	*/
	if (pos.x == 0 || pos.y == 0 || pos.x == dimension.x - 1 || pos.y == dimension.y - 1)
		return vec3(0, 1, 0);
	// otherwise, sample the four adjacent points.
	float heightPosX = getHeight(vec2(pos.x + sampleScale, pos.y));
	float heightPosY = getHeight(vec2(pos.x, pos.y + sampleScale));
	vec3 origin(pos.x, height, pos.y);
	vec3 xpos(pos.x + sampleScale, heightPosX, pos.y);
	vec3 ypos(pos.x, heightPosY, pos.y + sampleScale);
	vec3 seg0 = glm::normalize(xpos - origin);
	vec3 seg1 = glm::normalize(ypos - origin);
	vec3 ret(glm::normalize(glm::cross(seg1, seg0)));

	return ret;
}
// for sampling the normal at the tip, we need a different method.
vec3 SF_Heightmap::getNormal2(vec2 pos, float height){
	/* use this simple method to calculate the normal.
	sample the heights of the four adjacent points. if it's at the boundary,
	arbitrarily set the normal to pointing upwards, for now.
	*/
	if (pos.x == 0 || pos.y == 0 || pos.x == dimension.x - 1 || pos.y == dimension.y - 1)
		return vec3(0, 1, 0);
	// otherwise, sample the four adjacent points.
	float heightNegX = getHeight(vec2(pos.x - sampleScale, pos.y));
	float heightPosX = getHeight(vec2(pos.x + sampleScale, pos.y));
	float heightNegY = getHeight(vec2(pos.x, pos.y - sampleScale));
	float heightPosY = getHeight(vec2(pos.x, pos.y + sampleScale));
	vec3 xneg(pos.x - sampleScale, heightNegX, pos.y);
	vec3 yneg(pos.x, heightNegY, pos.y - sampleScale);
	vec3 xpos(pos.x + sampleScale, heightPosX, pos.y);
	vec3 ypos(pos.x, heightPosY, pos.y + sampleScale);
	vec3 seg0 = glm::normalize(xpos - xneg);
	vec3 seg1 = glm::normalize(ypos - yneg);
	vec3 ret(glm::normalize(glm::cross(seg1, seg0)));

	return ret;
}