[edit] I've updated the attached file on the first message because I find an error in one of the loops. Anyway, it fails the same way[/edit]
I tried to reproduce it in C, so I translate my test program to C:
1/* Testing 3D polygons. */
2
3#include <allegro.h>
4#include <stdio.h>
5#include <stdlib.h>
6
7
8 BITMAP *Texture, *BackBuffer;
9
10
11
12/* Creates a texture to be used by the cube. */
13 void CreateTexture (void)
14 {
15 int Black, White, Green;
16
17 Black = makecol (0, 0, 0);
18 White = makecol (255, 255, 255);
19 Green = makecol (0, 255, 0);
20 if (!(Texture = create_bitmap (32, 32)))
21 puts ("Can't create texture.");
22 clear_to_color (Texture, Black);
23 line (Texture, 0, 0, 31, 31, White);
24 line (Texture, 0, 32, 32, 0, White);
25 rect (Texture, 0, 0, 31, 31, White);
26 textout_ex (Texture, font, "dead", 0, 0, Green, -1);
27 textout_ex (Texture, font, "pigs", 0, 8, Green, -1);
28 textout_ex (Texture, font, "cant", 0, 16, Green, -1);
29 textout_ex (Texture, font, "fly.", 0, 24, Green, -1);
30 }
31
32
33
34/* This procedure tests the polygon. */
35 void DoTest (int aMode)
36 {
37 V3D_f Vertex[2], VertexR[2];
38 float Ax, Ay, Az,
39 Rx, Ry, Rz;
40 int Vtx;
41 MATRIX_f Matrix;
42
43 /* Vertex. */
44 Vertex[0].x = 0;
45 Vertex[1].x = -1;
46 Vertex[2].x = 1;
47 Vertex[0].y = 1;
48 Vertex[1].y = 0;
49 Vertex[2].y = 0;
50 Vertex[0].z = 0;
51 Vertex[1].z = 0;
52 Vertex[2].z = 0;
53 /* Texture mapping. */
54 Vertex[0].u = 15;
55 Vertex[1].u = 0;
56 Vertex[2].u = 31;
57 Vertex[0].v = 0;
58 Vertex[1].v = 31;
59 Vertex[2].v = 31;
60 for (Vtx=0; Vtx<3; ++Vtx) {
61 VertexR[Vtx].u = Vertex[Vtx].u;
62 VertexR[Vtx].v = Vertex[Vtx].v;
63 }
64 /* Angles. */
65 Ax = 0;
66 Ay = 0;
67 Az = 0;
68 Rx = (float)((rand () % 32) - 16) / 8;
69 Ry = (float)((rand () % 32) - 16) / 8;
70 Rz = (float)((rand () % 32) - 16) / 8;
71 /* Testing. */
72 do {
73 /* Animation. */
74 Ax += Rx;
75 Ay += Ry;
76 Az += Rz;
77printf ("<%d, %d, %d>\n", (int)Ax, (int)Ay, (int)Az);
78 get_transformation_matrix_f (&Matrix, 1, Ax, Ay, Az, 0, 0, -3);
79 for (Vtx=0; Vtx<3; ++Vtx) {
80 apply_matrix_f (&Matrix,
81 Vertex [Vtx].x, Vertex [Vtx].y, Vertex [Vtx].z,
82 &(VertexR[Vtx].x), &(VertexR[Vtx].y), &(VertexR[Vtx].z));
83 persp_project_f (VertexR[Vtx].x, VertexR[Vtx].y, VertexR[Vtx].z,
84 &(VertexR[Vtx].x), &(VertexR[Vtx].y));
85 }
86 /* Output. */
87 clear_bitmap (BackBuffer);
88 textout_centre_ex (BackBuffer, font,
89 aMode == POLYTYPE_ATEX ? "POLYTYPE_ATEX" : "POLYTYPE_PTEX",
90 160, 1, makecol (255, 255, 255), -1);
91 triangle3d_f (BackBuffer, aMode, Texture, &(VertexR[0]), &(VertexR[1]), &(VertexR[2]));
92 vsync;
93 blit (BackBuffer, screen, 0, 0, 0, 0, SCREEN_W, SCREEN_H);
94 } while (!keypressed ());
95 readkey (); /* Clear buffer. */
96 }
97
98
99
100int main (void) /* The program starts here. */
101{
102/* You should always do this at the start of Allegro programs. */
103 if (allegro_init () != 0) {
104 puts ("Can't initialize Allegro!");
105 return EXIT_FAILURE;
106 }
107 install_keyboard ();
108 install_timer ();
109
110/* Set a graphics mode sized 320x200. */
111 if (set_gfx_mode (GFX_AUTODETECT_WINDOWED, 320, 200, 0, 0) != 0)
112 if (set_gfx_mode (GFX_SAFE, 320, 200, 0, 0) != 0) {
113 set_gfx_mode (GFX_TEXT, 0, 0, 0, 0);
114 /* Show an error message. */
115 allegro_message ("Error setting graphics mode");
116 allegro_exit ();
117 return EXIT_FAILURE;
118 }
119 BackBuffer = create_bitmap (SCREEN_W, SCREEN_H);
120 CreateTexture ();
121 set_projection_viewport (0, 0, SCREEN_W, SCREEN_H);
122
123 DoTest (POLYTYPE_ATEX);
124 DoTest (POLYTYPE_PTEX);
125
126 destroy_bitmap (BackBuffer);
127 destroy_bitmap (Texture);
128 allegro_exit ();
129 return EXIT_SUCCESS;
130}
131
132END_OF_MAIN ();
I think it's a perfect translation of the Pascal program, but I don't know why it's so chaotic. 
