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Re-introduce earlier lintersect() work that was reverted.

Browse source 
engine.cpp/.h: clean up & fix lintersect().  Additionally, add support for finding intersections of collinear line segments.

This reverts r7290.

git-svn-id: https://svn.eduke32.com/eduke32@7471 1a8010ca-5511-0410-912e-c29ae57300e0
This commit is contained in:
pogokeen 2019-04-05 17:45:16 +00:00 committed by Christoph Oelckers
parent 24f43fe5a1
commit a82eb1d6fe
2 changed files with 69 additions and 48 deletions
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6
source/build/include/build.h
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@ -1240,8 +1240,10 @@ int32_t sectorofwall_noquick(int16_t wallNum);
int32_t loopnumofsector(int16_t sectnum, int16_t wallnum);
void setslope(int32_t sectnum, int32_t cf, int16_t slope);
int32_t lintersect(int32_t x1, int32_t y1, int32_t z1, int32_t x2, int32_t y2, int32_t z2, int32_t x3,
int32_t y3, int32_t x4, int32_t y4, int32_t *intx, int32_t *inty, int32_t *intz);
int32_t lintersect(int32_t originX, int32_t originY, int32_t originZ,
int32_t destX, int32_t destY, int32_t destZ,
int32_t lineStartX, int32_t lineStartY, int32_t lineEndX, int32_t lineEndY,
int32_t *intersectionX, int32_t *intersectionY, int32_t *intersectionZ);
int32_t rayintersect(int32_t x1, int32_t y1, int32_t z1, int32_t vx, int32_t vy, int32_t vz, int32_t x3,
int32_t y3, int32_t x4, int32_t y4, int32_t *intx, int32_t *inty, int32_t *intz);

111
source/build/src/engine.cpp
View file

@ -7432,56 +7432,75 @@ int32_t changespritestat(int16_t spritenum, int16_t newstatnum)
//
// lintersect (internal)
//
int32_t lintersect(int32_t x1, int32_t y1, int32_t z1,
int32_t x2, int32_t y2, int32_t z2,
int32_t x3, int32_t y3, int32_t x4, int32_t y4,
int32_t *intx, int32_t *inty, int32_t *intz)
int32_t lintersect(const int32_t originX, const int32_t originY, const int32_t originZ,
const int32_t destX, const int32_t destY, const int32_t destZ,
const int32_t lineStartX, const int32_t lineStartY, const int32_t lineEndX, const int32_t lineEndY,
int32_t *intersectionX, int32_t *intersectionY, int32_t *intersectionZ)
{
// p1 to p2 is a line segment
int32_t const x21 = x2 - x1;
int32_t const x34 = x3 - x4;
int32_t const y21 = y2 - y1;
int32_t const y34 = y3 - y4;
int32_t const bot = x21 * y34 - y21 * x34;
int32_t topt;
const vec2_t ray = { destX-originX,
destY-originY };
const vec2_t lineVec = { lineEndX-lineStartX,
lineEndY-lineStartY };
const vec2_t originDiff = { lineStartX-originX,
lineStartY-originY };
if (bot == 0)
const int32_t rayCrossLineVec = ray.x*lineVec.y - ray.y*lineVec.x;
const int32_t originDiffCrossRay = originDiff.x*ray.y - originDiff.y*ray.x;
if (rayCrossLineVec == 0)
{
if (originDiffCrossRay != 0)
{
// line segments are parallel
return 0;
}
// line segments are collinear
const int32_t rayLengthSquared = ray.x*ray.x + ray.y*ray.y;
const int32_t rayDotOriginDiff = ray.x*originDiff.x + ray.y*originDiff.y;
const int32_t rayDotLineEndDiff = rayDotOriginDiff + ray.x*lineVec.x + ray.y*lineVec.y;
int32_t t = min(rayDotOriginDiff, rayDotLineEndDiff);
if (rayDotOriginDiff < 0)
{
if (rayDotLineEndDiff < 0)
return 0;
t = 0;
}
else if (rayDotOriginDiff > rayLengthSquared)
{
if (rayDotLineEndDiff > rayLengthSquared)
return 0;
t = rayDotLineEndDiff;
}
t = divscale24(t, rayLengthSquared);
*intersectionX = originX + mulscale24(ray.x, t);
*intersectionY = originY + mulscale24(ray.y, t);
*intersectionZ = originZ + mulscale24(destZ-originZ, t);
return 1;
}
const int32_t originDiffCrossLineVec = originDiff.x*lineVec.y - originDiff.y*lineVec.x;
static const int32_t signBit = 1u<<31u;
// t is < 0 if (originDiffCrossLineVec^rayCrossLineVec) & signBit)
// t is > 1 if originDiffCrossLineVec > rayCrossLineVec
// u is < 0 if (originDiffCrossRay^rayCrossLineVec) & signBit
// u is > 1 if originDiffCrossRay > rayCrossLineVec
// where int32_t u = divscale24(originDiffCrossRay, rayCrossLineVec);
if (originDiffCrossLineVec > rayCrossLineVec ||
originDiffCrossRay > rayCrossLineVec ||
((originDiffCrossLineVec^rayCrossLineVec) & signBit) ||
((originDiffCrossRay^rayCrossLineVec) & signBit))
{
// line segments do not overlap
return 0;
else if (bot > 0)
{
int32_t x31 = x3 - x1;
int32_t y31 = y3 - y1;
topt = x31 * y34 - y31 * x34;
if ((unsigned)topt >= (unsigned)bot)
return 0;
int32_t topu = x21 * y31 - y21 * x31;
if ((unsigned)topu >= (unsigned)bot)
return 0;
}
else
{
int32_t x31 = x3 - x1;
int32_t y31 = y3 - y1;
topt = x31 * y34 - y31 * x34;
if ((unsigned)topt <= (unsigned)bot)
return 0;
int32_t topu = x21 * y31 - y21 * x31;
if ((unsigned)topu <= (unsigned)bot)
return 0;
}
int32_t t = divscale24(topt, bot);
*intx = x1 + mulscale24(x21, t);
*inty = y1 + mulscale24(y21, t);
*intz = z1 + mulscale24(z2 - z1, t);
int32_t t = divscale24(originDiffCrossLineVec, rayCrossLineVec);
*intersectionX = originX + mulscale24(ray.x, t);
*intersectionY = originY + mulscale24(ray.y, t);
*intersectionZ = originZ + mulscale24(destZ-originZ, t);
return 1;
}