1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
|
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define GL_GLEXT_PROTOTYPES
#include <GL/glut.h>
static const char *filename = NULL;
static GLuint nr_steps = 4;
static GLuint fragShader;
static GLuint vertShader;
static GLuint program;
static void usage( char *name )
{
fprintf( stderr, "usage: %s [ options ] shader_filename\n", name );
fprintf( stderr, "\n" );
fprintf( stderr, "options:\n" );
fprintf( stderr, " -f flat shaded\n" );
fprintf( stderr, " -nNr subdivision steps\n" );
}
static void load_and_compile_shader(GLuint shader, const char *text)
{
GLint stat;
glShaderSource(shader, 1, (const GLchar **) &text, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &stat);
if (!stat) {
GLchar log[1000];
GLsizei len;
glGetShaderInfoLog(shader, 1000, &len, log);
fprintf(stderr, "vp-tris: problem compiling shader:\n%s\n", log);
exit(1);
}
}
static void read_shader(GLuint shader, const char *filename)
{
const int max = 100*1000;
int n;
char *buffer = (char*) malloc(max);
FILE *f = fopen(filename, "r");
if (!f) {
fprintf(stderr, "vp-tris: Unable to open shader file %s\n", filename);
exit(1);
}
n = fread(buffer, 1, max, f);
printf("vp-tris: read %d bytes from shader file %s\n", n, filename);
if (n > 0) {
buffer[n] = 0;
load_and_compile_shader(shader, buffer);
}
fclose(f);
free(buffer);
}
static void check_link(GLuint prog)
{
GLint stat;
glGetProgramiv(prog, GL_LINK_STATUS, &stat);
if (!stat) {
GLchar log[1000];
GLsizei len;
glGetProgramInfoLog(prog, 1000, &len, log);
fprintf(stderr, "Linker error:\n%s\n", log);
}
}
static void prepare_shaders()
{
static const char *fragShaderText =
"void main() {\n"
" gl_FragColor = gl_Color;\n"
"}\n";
static const char *vertShaderText =
"void main() {\n"
" gl_FrontColor = gl_Color;\n"
" gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
"}\n";
fragShader = glCreateShader(GL_FRAGMENT_SHADER);
load_and_compile_shader(fragShader, fragShaderText);
vertShader = glCreateShader(GL_VERTEX_SHADER);
if (filename)
read_shader(vertShader, filename);
else
load_and_compile_shader(vertShader, vertShaderText);
program = glCreateProgram();
glAttachShader(program, fragShader);
glAttachShader(program, vertShader);
glLinkProgram(program);
check_link(program);
glUseProgram(program);
}
static void args(int argc, char *argv[])
{
GLint i;
for (i = 1; i < argc; i++) {
if (strncmp(argv[i], "-n", 2) == 0) {
nr_steps = atoi((argv[i]) + 2);
}
else if (strcmp(argv[i], "-f") == 0) {
glShadeModel(GL_FLAT);
}
else if (i == argc - 1) {
filename = argv[i];
}
else {
usage(argv[0]);
exit(1);
}
}
if (!filename) {
usage(argv[0]);
exit(1);
}
}
union vert {
struct {
GLfloat color[3];
GLfloat pos[3];
} v;
GLfloat f[6];
};
static void make_midpoint( union vert *out,
const union vert *v0,
const union vert *v1)
{
int i;
for (i = 0; i < 6; i++)
out->f[i] = v0->f[i] + .5 * (v1->f[i] - v0->f[i]);
}
static void subdiv( union vert *v0,
union vert *v1,
union vert *v2,
GLuint depth )
{
if (depth == 0) {
glColor3fv(v0->v.color);
glVertex3fv(v0->v.pos);
glColor3fv(v1->v.color);
glVertex3fv(v1->v.pos);
glColor3fv(v2->v.color);
glVertex3fv(v2->v.pos);
}
else {
union vert m[3];
make_midpoint(&m[0], v0, v1);
make_midpoint(&m[1], v1, v2);
make_midpoint(&m[2], v2, v0);
subdiv(&m[0], &m[2], v0, depth-1);
subdiv(&m[1], &m[0], v1, depth-1);
subdiv(&m[2], &m[1], v2, depth-1);
subdiv(&m[0], &m[1], &m[2], depth-1);
}
}
/** Assignment */
#define ASSIGN_3V( V, V0, V1, V2 ) \
do { \
V[0] = V0; \
V[1] = V1; \
V[2] = V2; \
} while(0)
static void Display( void )
{
glClearColor(0.3, 0.3, 0.3, 1);
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glUseProgram(program);
glBegin(GL_TRIANGLES);
{
union vert v[3];
ASSIGN_3V(v[0].v.color, 0,0,1);
ASSIGN_3V(v[0].v.pos, 0.9, -0.9, 0.0);
ASSIGN_3V(v[1].v.color, 1,0,0);
ASSIGN_3V(v[1].v.pos, 0.9, 0.9, 0.0);
ASSIGN_3V(v[2].v.color, 0,1,0);
ASSIGN_3V(v[2].v.pos, -0.9, 0, 0.0);
subdiv(&v[0], &v[1], &v[2], nr_steps);
}
glEnd();
glFlush();
}
static void Reshape( int width, int height )
{
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
/*glTranslatef( 0.0, 0.0, -15.0 );*/
}
static void CleanUp(void)
{
glDeleteShader(fragShader);
glDeleteShader(vertShader);
glDeleteProgram(program);
}
static void Key( unsigned char key, int x, int y )
{
(void) x;
(void) y;
switch (key) {
case 27:
CleanUp();
exit(0);
break;
}
glutPostRedisplay();
}
int main( int argc, char *argv[] )
{
glutInit( &argc, argv );
glutInitWindowPosition( 0, 0 );
glutInitWindowSize( 250, 250 );
glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH );
glutCreateWindow(argv[0]);
glutReshapeFunc( Reshape );
glutKeyboardFunc( Key );
glutDisplayFunc( Display );
args( argc, argv );
prepare_shaders();
glutMainLoop();
return 0;
}
|
