source: GTP/trunk/App/Demos/Illum/PathMap/Cylinder.cpp @ 896

#include "dxstdafx.h"
#include "cylinder.h"

bool Cylinder::intersectBackSide (const Ray& ray, float& depth, float rayMin, float rayMax)
{
        return false;
}

bool Cylinder::intersect (const Ray& ray, float& depth, float rayMin, float rayMax)
{
        lastTestedRayId = ray.id;
        lastTestedRayResult.isIntersect = false;
        Vector diff = (ray.origin - centre);
        diff.y = 0.0f;
        float b = 2.0f * (ray.dir * diff);
        float c = diff * diff - radius * radius;
        float a = ray.dir.x * ray.dir.x + ray.dir.z * ray.dir.z;

        float discriminant = b * b - 4.0f * a * c;
        if(discriminant < 0.0f)
                return false;
        else
        {
                float sqrtdisc = sqrtf(discriminant);
                float depth1 = (-b - sqrtdisc) * 0.5f / a;
                if(ray.origin.y + depth1 * ray.dir.y < top)
                {
                        if(ray.origin.y + depth1 * ray.dir.y > bottom)
                        {
                                depth = depth1;
                                lastTestedRayResult.isIntersect = true;
                                lastTestedRayResult.material    = this->material;
                                lastTestedRayResult.depth               = depth;
                                lastTestedRayResult.point = ray.origin + ray.dir * depth;
                                lastTestedRayResult.object = this;
                                lastTestedRayResult.normal.setDifference(lastTestedRayResult.point, centre);
                                lastTestedRayResult.normal.y = 0.0f;
                                lastTestedRayResult.normal *= 1.0f / radius;
                                return true;
                        }
                        else
                        {
                                float depth2 = (-b + sqrtdisc) * 0.5f / a;
                                float h = (bottom - ray.origin.y) / ray.dir.y;
                                if( h > depth1 && h < depth2)
                                {
                                        depth = h;
                                        lastTestedRayResult.normal = Vector(0.0f, -1.0f, 0.0f);
                                }
                                else
                                        return false;
                        }
                }
                else
                {
                        float depth2 = (-b + sqrtdisc) * 0.5f / a;
                        float h = (top - ray.origin.y) / ray.dir.y;
                        if( h > depth1 && h < depth2)
                        {
                                depth = h;
                                lastTestedRayResult.normal = Vector(0.0f, 1.0f, 0.0f);
                        }
                        else
                                return false;
                }

                lastTestedRayResult.isIntersect = true;
                lastTestedRayResult.material    = this->material;
                lastTestedRayResult.depth               = depth;
                lastTestedRayResult.point = ray.origin + ray.dir * depth;
                lastTestedRayResult.object = this;
                return true;
        }
}