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Fix incorrect rasterization at tile borders (#476)

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* Fix incorrect rasterization at tile borders

Clip the polygon at the tile border and disregard coordinates outside of
the tile before clamping.

* Added unit test with minimal repro case for the rasterization issue fixed in PR #476

Co-authored-by: Graham Pentheny <graham.pentheny@gmail.com>
This commit is contained in:
Piotr Piastucki 2022-11-23 08:42:03 +01:00 committed by GitHub
parent 2b0c244d12
commit 3901c5854c
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 45 additions and 4 deletions
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12
Recast/Source/RecastRasterization.cpp
View File

@ -264,7 +264,8 @@ static bool rasterizeTri(const float* v0, const float* v1, const float* v2,
// Calculate the footprint of the triangle on the grid's y-axis
int y0 = (int)((tmin[2] - bmin[2])*ics);
int y1 = (int)((tmax[2] - bmin[2])*ics);
y0 = rcClamp(y0, 0, h-1);
// use -1 rather than 0 to cut the polygon properly at the start of the tile
y0 = rcClamp(y0, -1, h-1);
y1 = rcClamp(y1, 0, h-1);
// Clip the triangle into all grid cells it touches.
@ -283,7 +284,7 @@ static bool rasterizeTri(const float* v0, const float* v1, const float* v2,
dividePoly(in, nvIn, inrow, &nvrow, p1, &nvIn, cz+cs, 2);
rcSwap(in, p1);
if (nvrow < 3) continue;
if (y < 0) continue;
// find the horizontal bounds in the row
float minX = inrow[0], maxX = inrow[0];
for (int i=1; i<nvrow; ++i)
@ -293,7 +294,10 @@ static bool rasterizeTri(const float* v0, const float* v1, const float* v2,
}
int x0 = (int)((minX - bmin[0])*ics);
int x1 = (int)((maxX - bmin[0])*ics);
x0 = rcClamp(x0, 0, w-1);
if (x1 < 0 || x0 >= w) {
continue;
}
x0 = rcClamp(x0, -1, w-1);
x1 = rcClamp(x1, 0, w-1);
int nv, nv2 = nvrow;
@ -305,7 +309,7 @@ static bool rasterizeTri(const float* v0, const float* v1, const float* v2,
dividePoly(inrow, nv2, p1, &nv, p2, &nv2, cx+cs, 0);
rcSwap(inrow, p2);
if (nv < 3) continue;
if (x < 0) continue;
// Calculate min and max of the span.
float smin = p1[1], smax = p1[1];
for (int i = 1; i < nv; ++i)

37
Tests/Recast/Tests_Recast.cpp
View File

@ -657,6 +657,43 @@ TEST_CASE("rcRasterizeTriangle")
}
}
TEST_CASE("rcRasterizeTriangle overlapping bb but non-overlapping triangle")
{
// This is a minimal repro case for the issue fixed in PR #476 (https://github.com/recastnavigation/recastnavigation/pull/476)
rcContext ctx;
// create a heightfield
float cellSize = 1;
float cellHeight = 1;
int width = 10;
int height = 10;
float bmin[] = { 0, 0, 0 };
float bmax[] = { 10, 10, 10 };
rcHeightfield heightfield;
REQUIRE(rcCreateHeightfield(&ctx, heightfield, width, height, bmin, bmax, cellSize, cellHeight));
// rasterize a triangle outside of the heightfield.
unsigned char area = 42;
int flagMergeThr = 1;
float verts[] =
{
-10.0, 5.5, -10.0,
-10.0, 5.5, 3,
3.0, 5.5, -10.0
};
REQUIRE(rcRasterizeTriangle(&ctx, &verts[0], &verts[3], &verts[6], area, heightfield, flagMergeThr));
// ensure that no spans were created
for (int x = 0; x < width; ++x)
{
for (int z = 0; z < height; ++z)
{
rcSpan* span = heightfield.spans[x + z * heightfield.width];
REQUIRE(span == NULL);
}
}
}
TEST_CASE("rcRasterizeTriangles")
{
rcContext ctx;