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Remove perspective divide for orthographic frustum #1728

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Remove perspective divide for orthographic frustum #1728

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12 changes: 12 additions & 0 deletions include/vsg/vk/State.h
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Original file line number Diff line number Diff line change
Expand Up @@ -223,6 +223,18 @@ namespace vsg
value_type f = -proj[1][1];
value_type sc = f * std::sqrt(square(mv[0][0]) + square(mv[1][0]) + square(mv[2][0]) + square(mv[0][1]) + square(mv[1][1]) + square(mv[2][1])) * 0.5;
value_type inv_scale = value_type(1.0) / sc;

// For an orthographic projection the projected size of a bounding sphere is independent of
// its distance from the eye (proj[2][3] == 0: there is no perspective divide). Using the
// eye-space depth as done below for perspective would make LOD selection and small-feature
// culling vary with distance, which is wrong for ortho, so use a constant lod distance
// derived purely from the projection scale.
if (proj[2][3] == value_type(0.0))
{
lodScale.set(value_type(0.0), value_type(0.0), value_type(0.0), inv_scale);
return;
}

lodScale.set(mv[0][2] * inv_scale,
mv[1][2] * inv_scale,
mv[2][2] * inv_scale,
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