private void CalculateTexCoordsAndWeightings(TextureBrush brush, Vector2[] texCoords, Vector2[] vertexPositions)
{
var min = new Vector2(float.MaxValue, float.MaxValue);
var max = new Vector2(float.MinValue, float.MinValue);
for (var v = 0; v < _numVertices; v++)
{
var vx = vertexPositions[v];
if (vx.X < min.X)
{
min.X = vx.X;
}
if (vx.Y < min.Y)
{
min.Y = vx.Y;
}
if (vx.X > max.X)
{
max.X = vx.X;
}
if (vx.Y > max.Y)
{
max.Y = vx.Y;
}
}
var areaSize = max - min;
var textureSize = Vector2.Zero;
if (brush.TextureScaling == TextureScaling.Tiled)
{
var size = _drawing.GetSurfaceDimensions(brush.Texture);
textureSize = new Vector2(size.Width, size.Height);
textureSize *= brush.TilingScale;
}
for (var v = 0; v < _numVertices; v++)
{
var vx = vertexPositions[v];
var position_fraction = (vx - min) / areaSize;
if (_fill == FillType.DualTextured)
{
_tex0Weightings[v] = CalculateTexture0WeightFromAreaPositionFraction(position_fraction);
}
switch (brush.TextureScaling)
{
case TextureScaling.Stretch:
position_fraction.Y = 1.0f - position_fraction.Y; //Flip Y to match origin for texcoords at topleft not bottomleft
texCoords[v] = position_fraction;
break;
case TextureScaling.Tiled:
var pixelDistanceFromCentre = position_fraction - new Vector2(0.5f, 0.5f);
pixelDistanceFromCentre *= areaSize;
var texSizeMultiplesFromCentre = pixelDistanceFromCentre / textureSize;
texSizeMultiplesFromCentre.Y = -texSizeMultiplesFromCentre.Y; //Switch from calcuation origin bottom left to top left
var texSizeMultiplesFromTopLeft = texSizeMultiplesFromCentre + new Vector2(0.5f, 0.5f);
texCoords[v] = texSizeMultiplesFromTopLeft;
break;
}
}
}