Dogcows Code - chaz/rasterize/blob - tri.h

   1
   2 /*
   3  * CS5600 University of Utah
   4  * Charles McGarvey
   5  * mcgarvey@eng.utah.edu
   6  */
   7
   8 #ifndef _TRI_H_
   9 #define _TRI_H_
  10
  11 #include "aabb.h"
  12 #include "mat.h"
  13 #include "vert.h"
  14
  15
  16 /*
  17  * A triangle is a polygon of three vertices.
  18  */
  19 struct tri
  20 {
  21     vert_t a;
  22     vert_t b;
  23     vert_t c;
  24 };
  25 typedef struct tri tri_t;
  26
  27 /*
  28  * Initialize a triangle.
  29  */
  30 INLINE_MAYBE
  31 void tri_init(tri_t* t, vert_t a, vert_t b, vert_t c)
  32 {
  33     t->a = a;
  34     t->b = b;
  35     t->c = c;
  36 }
  37
  38
  39 /*
  40  * Create a new triangle.
  41  */
  42 INLINE_MAYBE
  43 tri_t tri_new(vert_t a, vert_t b, vert_t c)
  44 {
  45     tri_t t;
  46     tri_init(&t, a, b, c);
  47     return t;
  48 }
  49
  50 #define TRI_ZERO tri_new(VERT_ZERO, VERT_ZERO, VERT_ZERO)
  51
  52
  53 /*
  54  * Create a new triangle on the heap.
  55  */
  56 INLINE_MAYBE
  57 tri_t* tri_alloc(vert_t a, vert_t b, vert_t c)
  58 {
  59     tri_t* t = (tri_t*)mem_alloc(sizeof(tri_t));
  60     tri_init(t, a, b, c);
  61     return t;
  62 }
  63
  64
  65 /*
  66  * Apply a transformation matrix to alter the triangle geometry.
  67  */
  68 INLINE_MAYBE
  69 tri_t tri_transform(tri_t t, mat_t m)
  70 {
  71     t.a.v = mat_apply(m, t.a.v);
  72     t.b.v = mat_apply(m, t.b.v);
  73     t.c.v = mat_apply(m, t.c.v);
  74     t.a.n.w = t.b.n.w = t.c.n.w = S(0.0);
  75     t.a.n = vec_normalize(mat_apply(m, t.a.n));
  76     t.b.n = vec_normalize(mat_apply(m, t.b.n));
  77     t.c.n = vec_normalize(mat_apply(m, t.c.n));
  78     return t;
  79 }
  80
  81 /*
  82  * Perform a homogeneous divide on the geometry.
  83  */
  84 INLINE_MAYBE
  85 tri_t tri_homodiv(tri_t t)
  86 {
  87     t.a.v = vec_homodiv(t.a.v);
  88     t.b.v = vec_homodiv(t.b.v);
  89     t.c.v = vec_homodiv(t.c.v);
  90     return t;
  91 }
  92
  93
  94 /*
  95  * Calculate a normal vector.
  96  */
  97 INLINE_MAYBE
  98 vec_t tri_normal(tri_t t)
  99 {
 100     vec_t n = vec_cross(vec_sub(t.b.v, t.a.v), vec_sub(t.c.v, t.a.v));
 101     return n;
 102 }
 103
 104
 105 /*
 106  * Calculate the AABB for the triangle.
 107  */
 108 INLINE_MAYBE
 109 aabb_t tri_aabb(tri_t t)
 110 {
 111     aabb_t b;
 112     b.min = vec_new(scal_min2(t.a.v.x, t.b.v.x, t.c.v.x),
 113                     scal_min2(t.a.v.y, t.b.v.y, t.c.v.y),
 114                     scal_min2(t.a.v.z, t.b.v.z, t.c.v.z));
 115     b.max = vec_new(scal_max2(t.a.v.x, t.b.v.x, t.c.v.x),
 116                     scal_max2(t.a.v.y, t.b.v.y, t.c.v.y),
 117                     scal_max2(t.a.v.z, t.b.v.z, t.c.v.z));
 118     return b;
 119 }
 120
 121
 122 /*
 123  * Get the barycentric coordinates of a vector against a triangle.  The
 124  * returned coordinates will be a linear combination, but they may not
 125  * actually be barycentric coordinates.  Use the function vec_is_barycentric
 126  * to check if they really are barycentric coordinates, meaning the point
 127  * vector v is inside the triangle, ignoring the Z components.
 128  */
 129 INLINE_MAYBE
 130 bool tri_barycentric(tri_t t, scal_t* b, vec_t v)
 131 {
 132     scal_t denom = (t.b.v.y - t.c.v.y) * (t.a.v.x - t.c.v.x) + (t.c.v.x - t.b.v.x) * (t.a.v.y - t.c.v.y);
 133     b[0] = ((t.b.v.y - t.c.v.y) * (v.x - t.c.v.x) + (t.c.v.x - t.b.v.x) * (v.y - t.c.v.y)) / denom;
 134     b[1] = ((t.c.v.y - t.a.v.y) * (v.x - t.c.v.x) + (t.a.v.x - t.c.v.x) * (v.y - t.c.v.y)) / denom;
 135     b[2] = S(1.0) - b[0] - b[1];
 136     if (S(0.0) <= b[0] && b[0] <= S(1.0) &&
 137         S(0.0) <= b[1] && b[1] <= S(1.0) &&
 138         S(0.0) <= b[2] && b[2] <= S(1.0)) {
 139         return true;
 140     }
 141     return false;
 142 }
 143
 144
 145 /*
 146  * Find the midpoint of the triangle.
 147  */
 148 INLINE_MAYBE
 149 vec_t tri_midpoint(tri_t t)
 150 {
 151     return vec_new((t.a.v.x + t.b.v.x + t.c.v.x) * S(0.333),
 152                    (t.a.v.y + t.b.v.y + t.c.v.y) * S(0.333),
 153                    (t.a.v.z + t.b.v.z + t.c.v.z) * S(0.333));
 154 }
 155
 156 /*
 157  * Get the average color of the triangle.
 158  */
 159 INLINE_MAYBE
 160 color_t tri_color(tri_t t)
 161 {
 162     scal_t b[] = {S(0.333), S(0.333), S(0.333)};
 163     return color_interp2(t.a.c, t.b.c, t.c.c, b);
 164 }
 165
 166
 167 /*
 168  * Get an interpolated z-value at the barycentric coordinates.
 169  */
 170 INLINE_MAYBE
 171 scal_t tri_z(tri_t t, scal_t b[3])
 172 {
 173     return t.a.v.z * b[0] + t.b.v.z * b[1] + t.c.v.z * b[2];
 174 }
 175
 176 /*
 177  * Calculate an interpolated point.
 178  */
 179 INLINE_MAYBE
 180 vec_t tri_point(tri_t t, scal_t b[3])
 181 {
 182     return vec_interp(t.a.v, t.b.v, t.c.v, b);
 183 }
 184
 185 /*
 186  * Calculate an interpolated normal.
 187  */
 188 INLINE_MAYBE
 189 vec_t tri_normal2(tri_t t, scal_t b[3])
 190 {
 191     return vec_normalize(vec_interp(t.a.n, t.b.n, t.c.n, b));
 192 }
 193
 194 /*
 195  * Calculate an interpolated texture coordinate.
 196  */
 197 INLINE_MAYBE
 198 vec_t tri_tcoord(tri_t t, scal_t b[3])
 199 {
 200 #if PERSPECTIVE_FIX
 201     return vec_tinterp(t.a.t, t.b.t, t.c.t, b);
 202 #else
 203     return vec_interp(t.a.t, t.b.t, t.c.t, b);
 204 #endif
 205 }
 206
 207 /*
 208  * Calculate an entirely new vertex within the triangle based on barycentric
 209  * coordinates.
 210  */
 211 INLINE_MAYBE
 212 vert_t tri_interp(tri_t t, scal_t b[3])
 213 {
 214     vert_t v = vert_new(tri_point(t, b));
 215     v.c = color_interp2(t.a.c, t.b.c, t.c.c, b);
 216     v.n = tri_normal2(t, b);
 217     v.t = tri_tcoord(t, b);
 218     return v;
 219 }
 220
 221
 222 #endif // _TRI_H_
 223