OpenSpace/modules/globebrowsing/shaders/tile.hglsl

/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2017                                                               *
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#ifndef TEXTURETILE_HGLSL
#define TEXTURETILE_HGLSL

// Must match the values in tiledataset.cpp
// (could be set as shader preprocessing data so that multiple definitions
// are not needed)
#define TILE_PIXEL_START_OFFSET #{tilePaddingStart}
#define TILE_PIXEL_SIZE_DIFFERENCE #{tilePaddingSizeDiff}

vec4 patchBorderOverlay(vec2 uv, vec3 borderColor, float borderSize) {
	vec2 uvOffset = uv - vec2(0.5);
	float thres = 0.5 - borderSize/2;
	bool isBorder = abs(uvOffset.x) > thres || abs(uvOffset.y) > thres;
	vec3 color = isBorder ? borderColor : vec3(0);
	return vec4(color, 0);
}


/////////////////////////////////////////////////////////////////////
//                       ChunkTile Depth Transform                      //
/////////////////////////////////////////////////////////////////////

struct TileDepthTransform {
    float depthScale;
    float depthOffset;
};

float getTransformedTexVal(const TileDepthTransform transform, const float val){
	return transform.depthOffset + transform.depthScale * val;
}

vec4 getTransformedTexVal(const TileDepthTransform transform, const vec4 val){
	return transform.depthOffset + transform.depthScale * val;
}

/////////////////////////////////////////////////////////////////////
//                        ChunkTile UV Transform                        //
/////////////////////////////////////////////////////////////////////

struct TileUvTransform {
    vec2 uvOffset;
    vec2 uvScale;
};


/////////////////////////////////////////////////////////////////////
//                              ChunkTile                               //
/////////////////////////////////////////////////////////////////////
struct ChunkTile {
	sampler2D textureSampler;
	TileUvTransform uvTransform;
};

vec2 compensateSourceTextureSampling(vec2 startOffset, vec2 sizeDiff, const ChunkTile chunkTile, vec2 tileUV){
	ivec2 resolution = textureSize(chunkTile.textureSampler, 0);

	vec2 sourceSize = vec2(resolution) + sizeDiff;
	vec2 currentSize = vec2(resolution);
	vec2 sourceToCurrentSize = currentSize / sourceSize;
	tileUV = sourceToCurrentSize * (tileUV - startOffset / sourceSize);
	return tileUV;
}

vec2 TileUVToTextureSamplePosition(const ChunkTile chunkTile, vec2 tileUV){
	vec2 uv = chunkTile.uvTransform.uvOffset + chunkTile.uvTransform.uvScale * tileUV;
	uv = compensateSourceTextureSampling(TILE_PIXEL_START_OFFSET, TILE_PIXEL_SIZE_DIFFERENCE, chunkTile, uv);
	return uv;
}

vec4 getTexVal(const ChunkTile chunkTile, vec2 tileUV){
	vec2 samplePosition = TileUVToTextureSamplePosition(chunkTile, tileUV);
	vec4 texVal = texture(chunkTile.textureSampler, samplePosition);
	return texVal;
}



/////////////////////////////////////////////////////////////////////
//                         Chunk Tile Pile                         //
/////////////////////////////////////////////////////////////////////
struct ChunkTilePile {
	ChunkTile chunkTile0;
	ChunkTile chunkTile1;
	ChunkTile chunkTile2;
};

struct LayerSettings {
	float opacity;
	float gamma;
	float multiplier;
};

struct Layer {
	ChunkTilePile pile;
	TileDepthTransform depthTransform;
	LayerSettings settings;
};

struct LevelWeights {
	float w1;
	float w2;
	float w3;
};

float getLevelInterpolationParameter(int chunkLevel, float distanceScaleFactor, float distToVertexOnEllipsoid){
	float projectedScaleFactor = distanceScaleFactor / distToVertexOnEllipsoid;
	float desiredLevel = log2(projectedScaleFactor);
	return chunkLevel - desiredLevel;
}

LevelWeights getLevelWeights(float levelInterpolationParameter){
	LevelWeights levelWeights;
	levelWeights.w1 = clamp(1 - levelInterpolationParameter, 0 , 1);
	levelWeights.w2 = (clamp(levelInterpolationParameter, 0 , 1) - clamp(levelInterpolationParameter - 1, 0 , 1));
	levelWeights.w3 = clamp(levelInterpolationParameter - 1, 0 , 1);
	return levelWeights;
}

LevelWeights getDefaultLevelWeights(){
	LevelWeights levelWeights;
	levelWeights.w1 = 1;
	levelWeights.w2 = 0;
	levelWeights.w3 = 0;
	return levelWeights;
}


vec4 getTexVal(const ChunkTilePile chunkTilePile, const LevelWeights w, const vec2 uv){
	return w.w1 * getTexVal(chunkTilePile.chunkTile0, uv) + 
		w.w2 * getTexVal(chunkTilePile.chunkTile1, uv) + 
		w.w3 * getTexVal(chunkTilePile.chunkTile2, uv);
}


#endif // TEXTURETILE_HGLSL