clipping.h

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#pragma once
 
#include <scimesh/types.h>
#include <scimesh/math_utils.h>
#include <vector>
 
namespace scimesh {
 
struct ClipVertex {
    Vec4 position;  
    Color color;    
    Vec3 normal;    
    Vec2 uv;        
};
 
int clip_triangle_near_plane(
    const ClipVertex &v0,
    const ClipVertex &v1,
    const ClipVertex &v2,
    std::vector<ClipVertex> &output_vertices,
    std::vector<Triangle> &output_triangles);
 
inline ClipPlane clip_plane_to_view_space(const ClipPlane &plane,
                                          const Vec3 &eye,
                                          const Mat4 &view) {
    ClipPlane out;
    out.space = plane.space;
 
    float len = glm::length(plane.normal);
    if (len < 1e-12f) {
        // Degenerate normal: keep everything (no clipping) instead of
        // discarding the whole scene.
        out.normal = Vec3(0.0f, 0.0f, 0.0f);
        out.offset = 0.0f;
        return out;
    }
 
    Vec3 n = plane.normal / len;
    out.normal = transform_direction(view, n);
    if (plane.space == PlaneSpace::WORLD) {
        // Shift the plane constant so that the cut stays at its world
        // position (see the derivation above).
        out.offset = glm::dot(n, eye) + plane.offset;
    } else {
        out.offset = plane.offset;
    }
    return out;
}
 
int clip_triangle_view_plane(
    const Vec3 &v0, const Vec3 &v1, const Vec3 &v2,
    const Vec3 &n0, const Vec3 &n1, const Vec3 &n2,
    const Color &c0, const Color &c1, const Color &c2,
    const Vec2 &uv0, const Vec2 &uv1, const Vec2 &uv2,
    const ClipPlane &plane,
    std::vector<ClipVertex> &output_vertices,
    std::vector<Triangle> &output_triangles);
 
} // namespace scimesh