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Implement line clipping for TextureProgress to avoid bad rendering due to imprecise UV mapping

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Original code used a quick aproximation for simulating the
correspondent texel in the `TextureProgress` texture as radial
progress indicator. This lead to visualization errors. Changed it for
a Liang-Barsky line clipping algorithm stripped to its minimum for
this specific use case.

Fix #17364.
This commit is contained in:
robfram 2018-03-10 20:51:42 +01:00
parent eceba5aa6a
commit 7991bd168d
1 changed files with 39 additions and 16 deletions
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55
scene/gui/texture_progress.cpp
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@ -117,22 +117,45 @@ Point2 TextureProgress::unit_val_to_uv(float val) {
Point2 p = get_relative_center();
if (val < 0.125)
return Point2(p.x + (1 - p.x) * val * 8, 0);
if (val < 0.25)
return Point2(1, p.y * (val - 0.125) * 8);
if (val < 0.375)
return Point2(1, p.y + (1 - p.y) * (val - 0.25) * 8);
if (val < 0.5)
return Point2(1 - (1 - p.x) * (val - 0.375) * 8, 1);
if (val < 0.625)
return Point2(p.x * (1 - (val - 0.5) * 8), 1);
if (val < 0.75)
return Point2(0, 1 - ((1 - p.y) * (val - 0.625) * 8));
if (val < 0.875)
return Point2(0, p.y - p.y * (val - 0.75) * 8);
else
return Point2(p.x * (val - 0.875) * 8, 0);
// Minimal version of Liang-Barsky clipping algorithm
float angle = (val * Math_TAU) - Math_PI * 0.5;
Point2 dir = Vector2(Math::cos(angle), Math::sin(angle));
float t1 = 1.0;
float cp;
float cq;
float cr;
float edgeLeft = 0.0;
float edgeRight = 1.0;
float edgeBottom = 0.0;
float edgeTop = 1.0;
for (int edge = 0; edge < 4; edge++) {
if (edge == 0) {
if (dir.x > 0)
continue;
cp = -dir.x;
cq = -(edgeLeft - p.x);
} else if (edge == 1) {
if (dir.x < 0)
continue;
cp = dir.x;
cq = (edgeRight - p.x);
} else if (edge == 2) {
if (dir.y > 0)
continue;
cp = -dir.y;
cq = -(edgeBottom - p.y);
} else if (edge == 3) {
if (dir.y < 0)
continue;
cp = dir.y;
cq = (edgeTop - p.y);
}
cr = cq / cp;
if (cr >= 0 && cr < t1)
t1 = cr;
}
return (p + t1 * dir);
}
Point2 TextureProgress::get_relative_center() {