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- Cull back facing triangles for the span drawers

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This commit is contained in:
Magnus Norddahl 2017-11-29 00:12:15 +01:00
parent fae514923a
commit f9fb4a0a17
2 changed files with 12 additions and 2 deletions
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13
src/polyrenderer/drawers/poly_triangle.cpp
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@ -243,6 +243,15 @@ bool PolyTriangleDrawer::is_degenerate(const ShadedTriVertex *vert)
return crosslengthsqr <= 1.e-6f;
}
bool PolyTriangleDrawer::is_frontfacing(TriDrawTriangleArgs *args)
{
float a =
args->v1->x * args->v2->y - args->v2->x * args->v1->y +
args->v2->x * args->v3->y - args->v3->x * args->v2->y +
args->v3->x * args->v1->y - args->v1->x * args->v3->y;
return a <= 0.0f;
}
void PolyTriangleDrawer::draw_shaded_triangle(const ShadedTriVertex *vert, bool ccw, TriDrawTriangleArgs *args, WorkerThreadData *thread)
{
// Reject triangle if degenerate
@ -324,7 +333,7 @@ void PolyTriangleDrawer::draw_shaded_triangle(const ShadedTriVertex *vert, bool
args->v1 = &clippedvert[numclipvert - 1];
args->v2 = &clippedvert[i - 1];
args->v3 = &clippedvert[i - 2];
if (args->CalculateGradients())
if (is_frontfacing(args) && args->CalculateGradients())
ScreenTriangle::Draw(args, thread);
}
}
@ -335,7 +344,7 @@ void PolyTriangleDrawer::draw_shaded_triangle(const ShadedTriVertex *vert, bool
args->v1 = &clippedvert[0];
args->v2 = &clippedvert[i - 1];
args->v3 = &clippedvert[i];
if (args->CalculateGradients())
if (!is_frontfacing(args) && args->CalculateGradients())
ScreenTriangle::Draw(args, thread);
}
}

1
src/polyrenderer/drawers/poly_triangle.h
View file

@ -44,6 +44,7 @@ private:
static void draw_arrays(const PolyDrawArgs &args, WorkerThreadData *thread);
static void draw_shaded_triangle(const ShadedTriVertex *vertices, bool ccw, TriDrawTriangleArgs *args, WorkerThreadData *thread);
static bool is_degenerate(const ShadedTriVertex *vertices);
static bool is_frontfacing(TriDrawTriangleArgs *args);
static int clipedge(const ShadedTriVertex *verts, ShadedTriVertex *clippedvert);