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Code Issues Releases Activity

Cleaned up Bresenham line in TLine and TEdgeManager.

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This commit is contained in:
Muzychenko Andrey 2022-05-17 12:36:46 +03:00
parent 2d2ca0ab2a
commit 0cb75ecf7f
2 changed files with 83 additions and 227 deletions
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128
SpaceCadetPinball/TLine.cpp
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@ -79,123 +79,45 @@ void TLine::place_in_grid()
{
if (dirY == 1)
{
if (yBox0 <= yBox1)
{
do
edgeMan->add_edge_to_box(xBox0, yBox0++, this);
while (yBox0 <= yBox1);
}
while (yBox0 <= yBox1)
edgeMan->add_edge_to_box(xBox0, yBox0++, this);
}
else if (yBox0 >= yBox1)
else
{
do
while (yBox0 >= yBox1)
edgeMan->add_edge_to_box(xBox0, yBox0--, this);
while (yBox0 >= yBox1);
}
}
else
{
float yCoord, xCoord;
int indexX1 = xBox0, indexY1 = yBox0;
int bresIndexX = xBox0 + 1, bresIndexY = yBox0 + 1;
auto bresDyDx = (Y0 - Y1) / (X0 - X1);
auto bresXAdd = Y0 - bresDyDx * X0;
edgeMan->add_edge_to_box(xBox0, yBox0, this);
if (dirX == 1)
// Bresenham line formula: y = dYdX * (x - x0) + y0; dYdX = (y0 - y1) / (x0 - x1)
auto dyDx = (Y0 - Y1) / (X0 - X1);
// Precompute constant part: dYdX * (-x0) + y0
auto precomp = -X0 * dyDx + Y0;
// X and Y indexes are offset by one when going forwards, not sure why
auto xBias = dirX == 1 ? 1 : 0, yBias = dirY == 1 ? 1 : 0;
for (auto indexX = xBox0, indexY = yBox0; indexX != xBox1 || indexY != yBox1;)
{
if (dirY == 1)
// Calculate y from indexY and from line formula
auto yDiscrete = (indexY + yBias) * edgeMan->AdvanceY + edgeMan->Y;
auto ylinear = ((indexX + xBias) * edgeMan->AdvanceX + edgeMan->X) * dyDx + precomp;
if (dirY == 1 ? ylinear >= yDiscrete : ylinear <= yDiscrete)
{
do
{
yCoord = bresIndexY * edgeMan->AdvanceY + edgeMan->Y;
xCoord = (bresIndexX * edgeMan->AdvanceX + edgeMan->X) * bresDyDx + bresXAdd;
if (xCoord >= yCoord)
{
if (xCoord == yCoord)
{
++indexX1;
++bresIndexX;
}
++indexY1;
++bresIndexY;
}
else
{
++indexX1;
++bresIndexX;
}
edgeMan->add_edge_to_box(indexX1, indexY1, this);
}
while (indexX1 != xBox1 || indexY1 != yBox1);
// Advance indexY when discrete value is ahead/behind
// Advance indexX when discrete value matches linear value
indexY += dirY;
if (ylinear == yDiscrete)
indexX += dirX;
}
else
{
do
{
yCoord = indexY1 * edgeMan->AdvanceY + edgeMan->Y;
xCoord = (bresIndexX * edgeMan->AdvanceX + edgeMan->X) * bresDyDx + bresXAdd;
if (xCoord <= yCoord)
{
if (xCoord == yCoord)
{
++indexX1;
++bresIndexX;
}
--indexY1;
}
else
{
++indexX1;
++bresIndexX;
}
edgeMan->add_edge_to_box(indexX1, indexY1, this);
}
while (indexX1 != xBox1 || indexY1 != yBox1);
}
}
else
{
if (dirY == 1)
{
do
{
xCoord = bresIndexY * edgeMan->AdvanceY + edgeMan->Y;
yCoord = (indexX1 * edgeMan->AdvanceX + edgeMan->X) * bresDyDx + bresXAdd;
if (yCoord >= xCoord)
{
if (yCoord == xCoord)
--indexX1;
++indexY1;
++bresIndexY;
}
else
{
--indexX1;
}
edgeMan->add_edge_to_box(indexX1, indexY1, this);
}
while (indexX1 != xBox1 || indexY1 != yBox1);
}
else
{
do
{
yCoord = indexY1 * edgeMan->AdvanceY + edgeMan->Y;
xCoord = (indexX1 * edgeMan->AdvanceX + edgeMan->X) * bresDyDx + bresXAdd;
if (xCoord <= yCoord)
{
if (xCoord == yCoord)
--indexX1;
--indexY1;
}
else
{
--indexX1;
}
edgeMan->add_edge_to_box(indexX1, indexY1, this);
}
while (indexX1 != xBox1 || indexY1 != yBox1);
// Advance indexX otherwise
indexX += dirX;
}
edgeMan->add_edge_to_box(indexX, indexY, this);
}
}
}