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this *should* fix the wonky clipping in gl_sky_clip 1 with skybox. won't fix 

wonky texturing or wonky sky rendering yet :(. anyway, can't find out for
certain until I get home.
This commit is contained in:
Bill Currie 2000-11-10 21:58:00 +00:00
parent 7bd99717d2
commit bc84e45835
1 changed files with 48 additions and 3 deletions
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51
source/gl_sky.c
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@ -305,6 +305,53 @@ determine_face (vec3_t v)
return i;
}
/*
find_intersect (for want of a better name)
finds the point of intersection of the plane formed by the eye and the two
points on the cube and the edge of the cube defined by the two faces.
Currently, this will break if the two points are not on adjoining cube
faces (ie either on opposing faces or the same face).
The equation for the point of intersection of a line and a plane is:
(x - p).n
y = x - _________ v
v.n
where n is the normal to the plane, p is a point on the plane, x is a
point on the line, and v is the direction vector of the line. n is found
by (x1 - e) cross (x2 - e) and p is taken to be e (e = eye coords) for
simplicity. However, because e is at 0,0,0, this simplifies to n = x1
cross x2 and p = 0,0,0, so the equation above simplifies to:
x.n
y = x - ___ v
v.n
*/
static void
find_intersect (int face1, vec3_t x1, int face2, vec3_t x2, vec3_t y)
{
vec3_t n; // normal to the plane formed by the eye and
// the two points on the cube.
vec3_t x = {0, 0, 0}; // point on cube edge of adjoining faces.
// always on an axis plane.
vec3_t v = {0, 0, 0}; // direction vector of cube edge. always +ve
vec_t x_n, v_n; // x.n and v.n
x[face1 % 3] = 2 * (face1 / 3) - 1;
x[face2 % 3] = 2 * (face2 / 3) - 1;
v[3 - ((face1 % 3) + (face2 % 3))] = 1;
CrossProduct (x1, x2, n);
x_n = DotProduct (x, n);
v_n = DotProduct (v, n);
VectorScale (v, x_n / v_n, v);
VectorSubtract (x, v, y);
}
static void
set_vertex (glpoly_t *p, vec3_t v, int face)
{
@ -375,9 +422,7 @@ R_DrawSkyBoxPoly (glpoly_t *poly)
// ouch, miss a face
} else {
vec3_t l;
VectorSubtract (v, last_v, l);
l[prev_face % 3] = 0;
VectorAdd (last_v, l, l);
find_intersect (prev_face, last_v, face, v, l);
set_vertex(&box[prev_face].poly, l, prev_face);
set_vertex(&box[face].poly, l, face);