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C/C++ Users Group Library 1996 July
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C-C++ Users Group Library July 1996.iso
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v_09_12
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9n12051a
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1991-10-13
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#include "solid.h"
void transform_object(struct solid_obj *obj_ptr)
/* Performs scaling, translation, rotation. */
{
struct facet *facet_ptr;
struct vertex *vertex_ptr;
int vertex_i, coord_index, facet_index;
float new_coord[3]; /* computed x, y, z coords */
float xa, ya, za; /* temporary variables */
struct vector normal; /* vector normal to facet */
/* perform scaling, then rotation, then translation
in that order, for each vertex in object */
for (vertex_ptr = obj_ptr->vertex_first, vertex_i =
0; vertex_i < defn_ptr[obj_ptr->obj_type]->
vertex_count; ++vertex_ptr, ++vertex_i) {
/* loop for each vertex in object */
/* scaling */
for (coord_index = 0; coord_index < 3;
++coord_index) {
new_coord[coord_index] = vertex_ptr->coord
[coord_index] * obj_ptr->scale;
}
/* rotation */
xa = cos(obj_ptr->YAW) * new_coord[0] -
sin(obj_ptr->YAW) * new_coord[2];
za = sin(obj_ptr->YAW) * new_coord[0] +
cos(obj_ptr->YAW) * new_coord[2];
new_coord[0] = cos(obj_ptr->ROLL) * xa +
sin(obj_ptr->ROLL) * new_coord[1];
ya = cos(obj_ptr->ROLL) * new_coord[1] -
sin(obj_ptr->ROLL) * xa;
new_coord[2] = cos(obj_ptr->PITCH) * za -
sin(obj_ptr->PITCH) * ya;
new_coord[1] = sin(obj_ptr->PITCH) * za +
cos(obj_ptr->PITCH) * ya;
/* translation; also insert new coordinates
into object */
for (coord_index = 0; coord_index < 3;
++coord_index) {
new_coord[coord_index] += obj_ptr->
xlate[coord_index];
vertex_ptr->coord[coord_index] =
new_coord[coord_index];
}
}
/* perform visibility test and projection on each
facet in object */
for (facet_ptr = defn_ptr[obj_ptr->obj_type]->
facet_first, facet_index = 0; facet_index <
defn_ptr[obj_ptr->obj_type]->facet_count;
++facet_index, facet_ptr = (struct facet *)
((char *)facet_ptr + sizeof(struct facet) +
facet_ptr->vertex_count * sizeof(INDEX))) {
/* loop for each facet in object */
normal = normal_vector(obj_ptr, facet_ptr);
vertex_ptr = obj_ptr->vertex_first + facet_ptr
->vertex_index[0];
obj_ptr->visible[facet_index] = (normal.x *
vertex_ptr->coord[0] + normal.y *
vertex_ptr->coord[0] + normal.z * (proj_z -
vertex_ptr->coord[0])) > 0.0;
display_facet(obj_ptr, facet_ptr, FALSE,
obj_ptr->visible[facet_index]);
/* projection without display */
}
}