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
|
/**
* Demonstration of doing triangle rasterization with a fragment program.
* Basic idea:
* 1. Draw screen-aligned quad / bounding box around the triangle verts.
* 2. For each pixel in the quad, determine if pixel is inside/outside
* the triangle edges.
*
* Brian Paul
* 1 Aug 2007
*/
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glew.h>
#include <GL/glut.h>
#include "shaderutil.h"
static GLint WinWidth = 300, WinHeight = 300;
static char *FragProgFile = NULL;
static char *VertProgFile = NULL;
static GLuint fragShader;
static GLuint vertShader;
static GLuint program;
static GLint win = 0;
static GLboolean anim = GL_TRUE;
static GLfloat Zrot = 0.0f;
static GLint uv0, uv1, uv2;
static const GLfloat TriVerts[3][2] = {
{ 50, 50 },
{ 250, 50 },
{ 150, 250 }
};
static void
RotateVerts(GLfloat a,
GLuint n, const GLfloat vertsIn[][2], GLfloat vertsOut[][2])
{
GLuint i;
GLfloat cx = WinWidth / 2, cy = WinHeight / 2;
for (i = 0; i < n; i++) {
float x = vertsIn[i][0] - cx;
float y = vertsIn[i][1] - cy;
vertsOut[i][0] = x * cos(a) + y * sin(a) + cx;
vertsOut[i][1] = -x * sin(a) + y * cos(a) + cy;
}
}
static void
ComputeBounds(GLuint n, GLfloat vertsIn[][2],
GLfloat *xmin, GLfloat *ymin,
GLfloat *xmax, GLfloat *ymax)
{
GLuint i;
*xmin = *xmax = vertsIn[0][0];
*ymin = *ymax = vertsIn[0][1];
for (i = 1; i < n; i++) {
if (vertsIn[i][0] < *xmin)
*xmin = vertsIn[i][0];
else if (vertsIn[i][0] > *xmax)
*xmax = vertsIn[i][0];
if (vertsIn[i][1] < *ymin)
*ymin = vertsIn[i][1];
else if (vertsIn[i][1] > *ymax)
*ymax = vertsIn[i][1];
}
}
static void
Redisplay(void)
{
GLfloat v[3][2], xmin, ymin, xmax, ymax;
RotateVerts(Zrot, 3, TriVerts, v);
ComputeBounds(3, v, &xmin, &ymin, &xmax, &ymax);
glUniform2fv(uv0, 1, v[0]);
glUniform2fv(uv1, 1, v[1]);
glUniform2fv(uv2, 1, v[2]);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glBegin(GL_POLYGON);
glVertex2f(xmin, ymin);
glVertex2f(xmax, ymin);
glVertex2f(xmax, ymax);
glVertex2f(xmin, ymax);
glEnd();
glPopMatrix();
glutSwapBuffers();
}
static void
Idle(void)
{
if (anim) {
Zrot = glutGet(GLUT_ELAPSED_TIME) * 0.0005;
glutPostRedisplay();
}
else
abort();
}
static void
Reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, 0, height, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
static void
CleanUp(void)
{
glDeleteShader(fragShader);
glDeleteShader(vertShader);
glDeleteProgram(program);
glutDestroyWindow(win);
}
static void
Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
switch(key) {
case ' ':
case 'a':
anim = !anim;
if (anim)
glutIdleFunc(Idle);
else
glutIdleFunc(NULL);
break;
case 'z':
Zrot = 0;
break;
case 's':
Zrot += 0.05;
break;
case 27:
CleanUp();
exit(0);
break;
}
glutPostRedisplay();
}
static void
Init(void)
{
static const char *fragShaderText =
"uniform vec2 v0, v1, v2; \n"
"float crs(const vec2 u, const vec2 v) \n"
"{ \n"
" return u.x * v.y - u.y * v.x; \n"
"} \n"
"\n"
"void main() {\n"
" vec2 p = gl_FragCoord.xy; \n"
" if (crs(v1 - v0, p - v0) >= 0.0 && \n"
" crs(v2 - v1, p - v1) >= 0.0 && \n"
" crs(v0 - v2, p - v2) >= 0.0) \n"
" gl_FragColor = vec4(1.0); \n"
" else \n"
" gl_FragColor = vec4(0.5); \n"
"}\n";
static const char *vertShaderText =
"void main() {\n"
" gl_Position = ftransform(); \n"
"}\n";
if (!ShadersSupported())
exit(1);
vertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
program = LinkShaders(vertShader, fragShader);
glUseProgram(program);
uv0 = glGetUniformLocation(program, "v0");
uv1 = glGetUniformLocation(program, "v1");
uv2 = glGetUniformLocation(program, "v2");
printf("Uniforms: %d %d %d\n", uv0, uv1, uv2);
/*assert(glGetError() == 0);*/
glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
glEnable(GL_DEPTH_TEST);
printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
assert(glIsProgram(program));
assert(glIsShader(fragShader));
assert(glIsShader(vertShader));
glColor3f(1, 0, 0);
}
static void
ParseOptions(int argc, char *argv[])
{
int i;
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-fs") == 0) {
FragProgFile = argv[i+1];
}
else if (strcmp(argv[i], "-vs") == 0) {
VertProgFile = argv[i+1];
}
}
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(WinWidth, WinHeight);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
win = glutCreateWindow(argv[0]);
glewInit();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Redisplay);
if (anim)
glutIdleFunc(Idle);
ParseOptions(argc, argv);
Init();
glutMainLoop();
return 0;
}
|
