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LibSoftGPU: Reduce Clipper class interface to minimum

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Much of the `Clipper` class can be made free functions and their scope
limited.

The purpose of this is to prepare the interface for a change to more
compile-time dispatch.
This commit is contained in:
Lenny Maiorani 2022-01-08 13:55:23 -07:00 • committed by Linus Groh
parent d1a87f1219
commit 25272cabef
2 changed files with 51 additions and 58 deletions
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78
Userland/Libraries/LibSoftGPU/Clipper.cpp
View file

@ -11,35 +11,44 @@
namespace SoftGPU {
bool Clipper::point_within_clip_plane(FloatVector4 const& vertex, ClipPlane plane) const
static constexpr FloatVector4 clip_plane_normals[] = {
{ 1, 0, 0, 0 }, // Left Plane
{ -1, 0, 0, 0 }, // Right Plane
{ 0, -1, 0, 0 }, // Top Plane
{ 0, 1, 0, 0 }, // Bottom plane
{ 0, 0, 1, 0 }, // Near Plane
{ 0, 0, -1, 0 } // Far Plane
};
static constexpr bool point_within_clip_plane(FloatVector4 const& vertex, Clipper::ClipPlane plane)
{
switch (plane) {
case ClipPlane::LEFT:
case Clipper::ClipPlane::LEFT:
return vertex.x() >= -vertex.w();
case ClipPlane::RIGHT:
case Clipper::ClipPlane::RIGHT:
return vertex.x() <= vertex.w();
case ClipPlane::TOP:
case Clipper::ClipPlane::TOP:
return vertex.y() <= vertex.w();
case ClipPlane::BOTTOM:
case Clipper::ClipPlane::BOTTOM:
return vertex.y() >= -vertex.w();
case ClipPlane::NEAR:
case Clipper::ClipPlane::NEAR:
return vertex.z() >= -vertex.w();
case ClipPlane::FAR:
case Clipper::ClipPlane::FAR:
return vertex.z() <= vertex.w();
}
return false;
}
Vertex Clipper::clip_intersection_point(Vertex const& p1, Vertex const& p2, ClipPlane plane_index) const
static Vertex clip_intersection_point(Vertex const& p1, Vertex const& p2, Clipper::ClipPlane plane)
{
// See https://www.microsoft.com/en-us/research/wp-content/uploads/1978/01/p245-blinn.pdf
// "Clipping Using Homogeneous Coordinates" Blinn/Newell, 1978
float const w1 = p1.clip_coordinates.w();
float const w2 = p2.clip_coordinates.w();
float const x1 = clip_plane_normals[plane_index].dot(p1.clip_coordinates);
float const x2 = clip_plane_normals[plane_index].dot(p2.clip_coordinates);
float const x1 = clip_plane_normals[to_underlying(plane)].dot(p1.clip_coordinates);
float const x2 = clip_plane_normals[to_underlying(plane)].dot(p2.clip_coordinates);
float const a = (w1 + x1) / ((w1 + x1) - (w2 + x2));
Vertex out;
@ -53,35 +62,40 @@ Vertex Clipper::clip_intersection_point(Vertex const& p1, Vertex const& p2, Clip
return out;
}
static void clip_plane(Vector<Vertex>& read_list, Vector<Vertex>& write_list, Clipper::ClipPlane plane)
{
auto read_from = &read_list;
auto write_to = &write_list;
write_to->clear_with_capacity();
// FIXME C++23. Static reflection will provide looping over all enum values.
for (size_t i = 0; i < read_from->size(); i++) {
auto const& curr_vec = read_from->at((i + 1) % read_from->size());
auto const& prev_vec = read_from->at(i);
if (point_within_clip_plane(curr_vec.clip_coordinates, plane)) {
if (!point_within_clip_plane(prev_vec.clip_coordinates, plane)) {
auto const intersect = clip_intersection_point(prev_vec, curr_vec, plane);
write_to->append(intersect);
}
write_to->append(curr_vec);
} else if (point_within_clip_plane(prev_vec.clip_coordinates, plane)) {
auto const intersect = clip_intersection_point(prev_vec, curr_vec, plane);
write_to->append(intersect);
}
}
swap(write_list, read_list);
}
void Clipper::clip_triangle_against_frustum(Vector<Vertex>& input_verts)
{
list_a = input_verts;
list_b.clear_with_capacity();
auto read_from = &list_a;
auto write_to = &list_b;
for (size_t plane = 0; plane < NUMBER_OF_CLIPPING_PLANES; plane++) {
write_to->clear_with_capacity();
// Save me, C++23
for (size_t i = 0; i < read_from->size(); i++) {
auto const& curr_vec = read_from->at((i + 1) % read_from->size());
auto const& prev_vec = read_from->at(i);
if (point_within_clip_plane(curr_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
if (!point_within_clip_plane(prev_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
auto const intersect = clip_intersection_point(prev_vec, curr_vec, static_cast<ClipPlane>(plane));
write_to->append(intersect);
}
write_to->append(curr_vec);
} else if (point_within_clip_plane(prev_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
auto const intersect = clip_intersection_point(prev_vec, curr_vec, static_cast<ClipPlane>(plane));
write_to->append(intersect);
}
}
swap(write_to, read_from);
clip_plane(list_a, list_b, static_cast<ClipPlane>(plane));
}
input_verts = *read_from;
input_verts = list_a;
}
}

31
Userland/Libraries/LibSoftGPU/Clipper.h
View file

@ -13,7 +13,10 @@
namespace SoftGPU {
class Clipper final {
enum ClipPlane : u8 {
static constexpr u8 NUMBER_OF_CLIPPING_PLANES = 6;
public:
enum class ClipPlane : u8 {
LEFT = 0,
RIGHT,
TOP,
@ -22,35 +25,11 @@ class Clipper final {
FAR
};
static constexpr u8 NUMBER_OF_CLIPPING_PLANES = 6;
static constexpr u8 MAX_CLIPPED_VERTS = 6;
static constexpr FloatVector4 clip_planes[] = {
{ -1, 0, 0, 1 }, // Left Plane
{ 1, 0, 0, 1 }, // Right Plane
{ 0, 1, 0, 1 }, // Top Plane
{ 0, -1, 0, 1 }, // Bottom plane
{ 0, 0, 1, 1 }, // Near Plane
{ 0, 0, -1, 1 } // Far Plane
};
static constexpr FloatVector4 clip_plane_normals[] = {
{ 1, 0, 0, 0 }, // Left Plane
{ -1, 0, 0, 0 }, // Right Plane
{ 0, -1, 0, 0 }, // Top Plane
{ 0, 1, 0, 0 }, // Bottom plane
{ 0, 0, 1, 0 }, // Near Plane
{ 0, 0, -1, 0 } // Far Plane
};
public:
Clipper() { }
Clipper() = default;
void clip_triangle_against_frustum(Vector<Vertex>& input_vecs);
private:
bool point_within_clip_plane(FloatVector4 const& vertex, ClipPlane plane) const;
Vertex clip_intersection_point(Vertex const& vec, Vertex const& prev_vec, ClipPlane plane_index) const;
Vector<Vertex> list_a;
Vector<Vertex> list_b;
};