/*
 * This is a very simple demonstration of how to provide procedural textures to Demeter.
 * This sample texture factory simply creates texels based on the terrain elevation at each texel.
 * Colors become more yellow at higher elevations and more blue at lower elevations.
 * For more interesting procedural texture algorithms and ideas, see the Open Mountains website
 * (openmountains.sourceforge.net) for some good ideas and some good links.
 */

#include "SampleTextureFactory.h"

using namespace Demeter;
using namespace std;

const float texelsPerMeter = 1.0f;
const float texelSpacing = 1.0f / texelsPerMeter;
const float textureSize = 256.0f;

SampleTextureFactory::SampleTextureFactory(Terrain * pTerrain)
{
	m_pTerrain = pTerrain;
}

SampleTextureFactory::~SampleTextureFactory()
{
}

Texture *SampleTextureFactory::GetTexture(int index, float originX, float originY, float width, float height)
{
	// The Demeter terrain calls this method when a texture has become visible and needs to be rendered.
	// Your implementation of TextureFactory must return a valid OpenGL texture, generated by whatever
	// means you like. Notice that a map of textures is kept as a cache so that subsequent requests for this
	// texture will be nearly instantaneous. You don't have to do this (e.g. for extremely large terrains
	// it wouldn't be practical), but you need some kind of strategy to keep your texture requests fast since
	// they happen at runtime.
	float texelSpacing = width / textureSize;
	Texture *pTexture = m_Textures[index];
	if (pTexture == NULL)
	{
		cout << "SAMPLETEXTUREFACTORY: width = " << width << " height = " << height << endl;
		cout << "SAMPLETEXTUREFACTORY: texelSpacing = " << texelSpacing << endl;
		cout << "SAMPLETEXTUREFACTORY: texture size = " << (int)((textureSize + 1.0f) * (textureSize + 1.0f)) * 4 << " bytes" << endl;
		// Allocate an extra row and column to protect from float precision error.
		Uint8 *pImage = new Uint8[(int)((textureSize + 1.0f) * (textureSize + 1.0f)) * 3];
		int imageIndex = 0;
		for (float y = originY; y < originY + height; y += texelSpacing)
		{
			for (float x = originX; x < originX + width; x += texelSpacing, imageIndex += 3)
			{
				float elev = m_pTerrain->GetElevation(x, y);
				Uint8 red = (Uint8) (255.0f * elev / m_pTerrain->GetMaxElevation());
				Uint8 green = (Uint8) (255.0f * elev / m_pTerrain->GetMaxElevation());
				Uint8 blue = (Uint8) 255 - (Uint8) (255.0f * elev / m_pTerrain->GetMaxElevation());
				pImage[imageIndex] = red;
				pImage[imageIndex + 1] = green;
				pImage[imageIndex + 2] = blue;
			}
		}
		pTexture = new Texture(pImage, (int)textureSize, (int)textureSize, (int)textureSize, 0, true, false, false);
		m_Textures[index] = pTexture;
		delete[]pImage;
	}
	return pTexture;
}

void SampleTextureFactory::UnloadTexture(int index)
{
	// Called by the Demeter terrain when a texture is no longer visible.
	// We could unload the texture here, set it to a lower priority for OpenGL, etc.
	// m_Textures[index]->UnloadTexture();
	// Keep the texture for now ...
}