William Moberg
77 lines
2.4 KiB
C++
77 lines
2.4 KiB
C++
#ifndef Frustum_h__
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#define Frustum_h__
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#include "../GLM.h"
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#include "AABB.h"
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#include <bitset>
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//A frustum defined by 6 planes.
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struct Frustum
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{
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//Contains points P in: dot(normal, P) + d = 0
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struct Plane
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{
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glm::vec3 Normal;
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float Distance;
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};
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enum class Output
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{
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Inside,
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Outside,
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Intersects
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};
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Plane Planes[6];
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Frustum() = default;
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Frustum(glm::mat4x4 viewProjMatrix)
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{
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//Order: Right, left, top, bottom, far, near.
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int sign = 1;
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for (int i = 0; i < 6; ++i) {
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sign = -sign;
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int index = i / 2;
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Plane& plane = Planes[i];
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plane.Normal.x = viewProjMatrix[0].w + sign * viewProjMatrix[0][index];
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plane.Normal.y = viewProjMatrix[1].w + sign * viewProjMatrix[1][index];
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plane.Normal.z = viewProjMatrix[2].w + sign * viewProjMatrix[2][index];
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plane.Distance = viewProjMatrix[3].w + sign * viewProjMatrix[3][index];
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float divByNormalLength = 1.0f / glm::length(plane.Normal);
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plane.Normal *= divByNormalLength;
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plane.Distance *= divByNormalLength;
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}
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}
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Output VsAABB(const AABB& box) const
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{
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const glm::vec3& maxCorner = box.MaxCorner();
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const glm::vec3& minCorner = box.MinCorner();
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bool completelyInside = true;
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for (const Plane& p : Planes) {
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bool anyWasInside = false;
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bool anyWasOutside = false;
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//If points are on both sides of the plane, we can stop.
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for (int i = 0; i < 8 && (!anyWasInside || !anyWasOutside); ++i) {
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std::bitset<3> bits(i);
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glm::vec3 corner;
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corner.x = bits.test(0) ? maxCorner.x : minCorner.x;
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corner.y = bits.test(1) ? maxCorner.y : minCorner.y;
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corner.z = bits.test(2) ? maxCorner.z : minCorner.z;
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if (glm::dot(p.Normal, corner) > -p.Distance) {
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anyWasInside = true;
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} else {
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anyWasOutside = true;
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}
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}
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if (!anyWasInside) {
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return Output::Outside;
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}
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if (anyWasOutside) {
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completelyInside = false;
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}
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}
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return completelyInside ? Output::Inside : Output::Intersects;
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}
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};
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#endif |