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https://github.com/RGBCube/serenity
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fef7f7159c
This follows the OpenGL 1.5 spec much more closely. We need to store the eye coordinates especially, since they are used in texture coordinate generation and fog fragment depth calculation.
85 lines
3 KiB
C++
85 lines
3 KiB
C++
/*
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* Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
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* Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Format.h>
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#include <AK/ScopeGuard.h>
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#include <LibSoftGPU/Clipper.h>
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namespace SoftGPU {
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bool Clipper::point_within_clip_plane(const FloatVector4& vertex, ClipPlane plane)
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{
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switch (plane) {
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case ClipPlane::LEFT:
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return vertex.x() >= -vertex.w();
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case ClipPlane::RIGHT:
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return vertex.x() <= vertex.w();
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case ClipPlane::TOP:
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return vertex.y() <= vertex.w();
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case ClipPlane::BOTTOM:
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return vertex.y() >= -vertex.w();
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case ClipPlane::NEAR:
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return vertex.z() >= -vertex.w();
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case ClipPlane::FAR:
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return vertex.z() <= vertex.w();
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}
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return false;
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}
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Vertex Clipper::clip_intersection_point(const Vertex& p1, const Vertex& p2, ClipPlane plane_index)
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{
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// See https://www.microsoft.com/en-us/research/wp-content/uploads/1978/01/p245-blinn.pdf
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// "Clipping Using Homogeneous Coordinates" Blinn/Newell, 1978
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float w1 = p1.clip_coordinates.w();
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float w2 = p2.clip_coordinates.w();
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float x1 = clip_plane_normals[plane_index].dot(p1.clip_coordinates);
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float x2 = clip_plane_normals[plane_index].dot(p2.clip_coordinates);
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float a = (w1 + x1) / ((w1 + x1) - (w2 + x2));
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Vertex out;
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out.position = p1.position * (1 - a) + p2.position * a;
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out.eye_coordinates = p1.eye_coordinates * (1 - a) + p2.eye_coordinates * a;
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out.clip_coordinates = p1.clip_coordinates * (1 - a) + p2.clip_coordinates * a;
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out.color = p1.color * (1 - a) + p2.color * a;
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out.tex_coord = p1.tex_coord * (1 - a) + p2.tex_coord * a;
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return out;
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}
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void Clipper::clip_triangle_against_frustum(Vector<Vertex>& input_verts)
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{
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list_a = input_verts;
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list_b.clear_with_capacity();
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auto read_from = &list_a;
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auto write_to = &list_b;
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for (size_t plane = 0; plane < NUMBER_OF_CLIPPING_PLANES; plane++) {
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write_to->clear_with_capacity();
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// Save me, C++23
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for (size_t i = 0; i < read_from->size(); i++) {
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const auto& curr_vec = read_from->at((i + 1) % read_from->size());
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const auto& prev_vec = read_from->at(i);
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if (point_within_clip_plane(curr_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
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if (!point_within_clip_plane(prev_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
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auto intersect = clip_intersection_point(prev_vec, curr_vec, static_cast<ClipPlane>(plane));
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write_to->append(intersect);
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}
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write_to->append(curr_vec);
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} else if (point_within_clip_plane(prev_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
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auto intersect = clip_intersection_point(prev_vec, curr_vec, static_cast<ClipPlane>(plane));
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write_to->append(intersect);
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}
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}
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swap(write_to, read_from);
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}
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input_verts = *read_from;
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}
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}
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