61 lines
2.3 KiB
C
61 lines
2.3 KiB
C
#include "frustum.h"
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#include <math.h>
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void frustum_from_matrix(const Mat4* vp, Vec4 planes[6]) {
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// 行主序存储：clip = vec4(pos,1) * vp
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// 因此 clip 分量 = dot(pos, vp 的列)
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// left = col3 + col0
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// right = col3 - col0
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// bottom = col3 + col1
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// top = col3 - col1
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// near = col3 + col2
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// far = col3 - col2
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planes[0] = (Vec4){ vp->m[0][3] + vp->m[0][0],
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vp->m[1][3] + vp->m[1][0],
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vp->m[2][3] + vp->m[2][0],
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vp->m[3][3] + vp->m[3][0] };
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planes[1] = (Vec4){ vp->m[0][3] - vp->m[0][0],
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vp->m[1][3] - vp->m[1][0],
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vp->m[2][3] - vp->m[2][0],
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vp->m[3][3] - vp->m[3][0] };
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planes[2] = (Vec4){ vp->m[0][3] + vp->m[0][1],
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vp->m[1][3] + vp->m[1][1],
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vp->m[2][3] + vp->m[2][1],
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vp->m[3][3] + vp->m[3][1] };
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planes[3] = (Vec4){ vp->m[0][3] - vp->m[0][1],
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vp->m[1][3] - vp->m[1][1],
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vp->m[2][3] - vp->m[2][1],
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vp->m[3][3] - vp->m[3][1] };
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planes[4] = (Vec4){ vp->m[0][3] + vp->m[0][2],
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vp->m[1][3] + vp->m[1][2],
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vp->m[2][3] + vp->m[2][2],
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vp->m[3][3] + vp->m[3][2] };
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planes[5] = (Vec4){ vp->m[0][3] - vp->m[0][2],
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vp->m[1][3] - vp->m[1][2],
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vp->m[2][3] - vp->m[2][2],
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vp->m[3][3] - vp->m[3][2] };
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for (int i = 0; i < 6; i++) {
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float len = sqrtf(planes[i].x * planes[i].x +
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planes[i].y * planes[i].y +
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planes[i].z * planes[i].z);
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if (len > 0.0001f) {
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planes[i].x /= len;
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planes[i].y /= len;
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planes[i].z /= len;
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planes[i].w /= len;
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}
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}
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}
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int frustum_intersects_sphere(const Vec4 planes[6], Vec3 center, float radius) {
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for (int i = 0; i < 6; i++) {
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float dist = planes[i].x * center.x +
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planes[i].y * center.y +
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planes[i].z * center.z +
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planes[i].w;
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if (dist < -radius) return 0;
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}
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return 1;
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}
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