1/**
2 * Vertex shader texture sampling test.
3 * Brian Paul
4 * 2 Dec 2008
5 */
6
7#include <assert.h>
8#include <string.h>
9#include <stdio.h>
10#include <stdlib.h>
11#include <math.h>
12#include <GL/glew.h>
13#include "glut_wrap.h"
14#include "shaderutil.h"
15
16
17static const char *VertShaderText =
18   "uniform sampler2D tex1; \n"
19   "void main() \n"
20   "{ \n"
21   "   vec4 pos = gl_Vertex; \n"
22   "   pos.z = texture2D(tex1, gl_MultiTexCoord0.xy).x - 0.5; \n"
23   "   gl_Position = gl_ModelViewProjectionMatrix * pos; \n"
24   "   gl_FrontColor = pos; \n"
25   "} \n";
26
27static const char *FragShaderText =
28   "void main() \n"
29   "{ \n"
30   "   gl_FragColor = gl_Color; \n"
31   "} \n";
32
33
34static GLuint fragShader;
35static GLuint vertShader;
36static GLuint program;
37
38static GLint win = 0;
39static GLboolean Anim = GL_TRUE;
40static GLboolean WireFrame = GL_TRUE;
41static GLfloat xRot = -70.0f, yRot = 0.0f, zRot = 0.0f;
42
43static void
44Idle(void)
45{
46   zRot = 90 + glutGet(GLUT_ELAPSED_TIME) * 0.05;
47   glutPostRedisplay();
48}
49
50
51static void
52DrawMesh(void)
53{
54   GLfloat xmin = -2.0, xmax = 2.0;
55   GLfloat ymin = -2.0, ymax = 2.0;
56   GLuint xdivs = 20, ydivs = 20;
57   GLfloat dx = (xmax - xmin) / xdivs;
58   GLfloat dy = (ymax - ymin) / ydivs;
59   GLfloat ds = 1.0 / xdivs, dt = 1.0 / ydivs;
60   GLfloat x, y, s, t;
61   GLuint i, j;
62
63   y = ymin;
64   t = 0.0;
65   for (i = 0; i < ydivs; i++) {
66      x = xmin;
67      s = 0.0;
68      glBegin(GL_QUAD_STRIP);
69      for (j = 0; j < xdivs; j++) {
70         glTexCoord2f(s, t);
71         glVertex2f(x, y);
72         glTexCoord2f(s, t + dt);
73         glVertex2f(x, y + dy);
74         x += dx;
75         s += ds;
76      }
77      glEnd();
78      y += dy;
79      t += dt;
80   }
81}
82
83
84static void
85Redisplay(void)
86{
87   if (WireFrame)
88      glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
89   else
90      glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
91
92   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
93
94   glPushMatrix();
95   glRotatef(xRot, 1.0f, 0.0f, 0.0f);
96   glRotatef(yRot, 0.0f, 1.0f, 0.0f);
97   glRotatef(zRot, 0.0f, 0.0f, 1.0f);
98
99   glPushMatrix();
100   DrawMesh();
101   glPopMatrix();
102
103   glPopMatrix();
104
105   glutSwapBuffers();
106}
107
108
109static void
110Reshape(int width, int height)
111{
112   glViewport(0, 0, width, height);
113   glMatrixMode(GL_PROJECTION);
114   glLoadIdentity();
115   glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
116   glMatrixMode(GL_MODELVIEW);
117   glLoadIdentity();
118   glTranslatef(0.0f, 0.0f, -15.0f);
119}
120
121
122static void
123CleanUp(void)
124{
125   glDeleteShader(fragShader);
126   glDeleteShader(vertShader);
127   glDeleteProgram(program);
128   glutDestroyWindow(win);
129}
130
131
132static void
133Key(unsigned char key, int x, int y)
134{
135   const GLfloat step = 2.0;
136  (void) x;
137  (void) y;
138
139   switch(key) {
140   case 'a':
141      Anim = !Anim;
142      if (Anim)
143         glutIdleFunc(Idle);
144      else
145         glutIdleFunc(NULL);
146      break;
147   case 'w':
148      WireFrame = !WireFrame;
149      break;
150   case 'z':
151      zRot += step;
152      break;
153   case 'Z':
154      zRot -= step;
155      break;
156   case 27:
157      CleanUp();
158      exit(0);
159      break;
160   }
161   glutPostRedisplay();
162}
163
164
165static void
166SpecialKey(int key, int x, int y)
167{
168   const GLfloat step = 2.0;
169
170  (void) x;
171  (void) y;
172
173   switch(key) {
174   case GLUT_KEY_UP:
175      xRot += step;
176      break;
177   case GLUT_KEY_DOWN:
178      xRot -= step;
179      break;
180   case GLUT_KEY_LEFT:
181      yRot -= step;
182      break;
183   case GLUT_KEY_RIGHT:
184      yRot += step;
185      break;
186   }
187   glutPostRedisplay();
188}
189
190
191static void
192MakeTexture(void)
193{
194   const GLuint texWidth = 64, texHeight = 64;
195   GLfloat texImage[64][64];
196   GLuint i, j;
197
198   /* texture is basically z = f(x, y) */
199   for (i = 0; i < texHeight; i++) {
200      GLfloat y = 2.0 * (i / (float) (texHeight - 1)) - 1.0;
201      for (j = 0; j < texWidth; j++) {
202         GLfloat x = 2.0 * (j / (float) (texWidth - 1)) - 1.0;
203         GLfloat z = 0.5 + 0.5 * (sin(4.0 * x) * sin(4.0 * y));
204         texImage[i][j] = z;
205      }
206   }
207
208   glActiveTexture(GL_TEXTURE0);
209   glBindTexture(GL_TEXTURE_2D, 42);
210   glTexImage2D(GL_TEXTURE_2D, 0, GL_INTENSITY, texWidth, texHeight, 0,
211                GL_LUMINANCE, GL_FLOAT, texImage);
212   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
213   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
214}
215
216
217static void
218Init(void)
219{
220   GLint m;
221
222   glGetIntegerv(GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS_ARB, &m);
223   if (m < 1) {
224      printf("Error: no vertex shader texture units supported.\n");
225      exit(1);
226   }
227
228   if (!ShadersSupported())
229      exit(1);
230
231   vertShader = CompileShaderText(GL_VERTEX_SHADER, VertShaderText);
232   fragShader = CompileShaderText(GL_FRAGMENT_SHADER, FragShaderText);
233   program = LinkShaders(vertShader, fragShader);
234
235   glUseProgram(program);
236
237   assert(glGetError() == 0);
238
239   MakeTexture();
240
241   glClearColor(0.4f, 0.4f, 0.8f, 0.0f);
242
243   glEnable(GL_DEPTH_TEST);
244
245   glColor3f(1, 1, 1);
246}
247
248
249int
250main(int argc, char *argv[])
251{
252   glutInit(&argc, argv);
253   glutInitWindowSize(500, 500);
254   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
255   win = glutCreateWindow(argv[0]);
256   glewInit();
257   glutReshapeFunc(Reshape);
258   glutKeyboardFunc(Key);
259   glutSpecialFunc(SpecialKey);
260   glutDisplayFunc(Redisplay);
261   Init();
262   if (Anim)
263      glutIdleFunc(Idle);
264   glutMainLoop();
265   return 0;
266}
267
268