1//
2// Book:      OpenGL(R) ES 2.0 Programming Guide
3// Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
4// ISBN-10:   0321502795
5// ISBN-13:   9780321502797
6// Publisher: Addison-Wesley Professional
7// URLs:      http://safari.informit.com/9780321563835
8//            http://www.opengles-book.com
9//
10
11// TextureWrap.c
12//
13//    This is an example that demonstrates the three texture
14//    wrap modes available on 2D textures
15//
16#include <stdlib.h>
17#include "esUtil.h"
18
19typedef struct
20{
21   // Handle to a program object
22   GLuint programObject;
23
24   // Attribute locations
25   GLint  positionLoc;
26   GLint  texCoordLoc;
27
28   // Sampler location
29   GLint samplerLoc;
30
31   // Offset location
32   GLint offsetLoc;
33
34   // Texture handle
35   GLuint textureId;
36
37} UserData;
38
39///
40//  Generate an RGB8 checkerboard image
41//
42GLubyte* GenCheckImage( int width, int height, int checkSize )
43{
44   int x,
45       y;
46   GLubyte *pixels = malloc( width * height * 3 );
47
48   if ( pixels == NULL )
49      return NULL;
50
51   for ( y = 0; y < height; y++ )
52      for ( x = 0; x < width; x++ )
53      {
54         GLubyte rColor = 0;
55         GLubyte bColor = 0;
56
57         if ( ( x / checkSize ) % 2 == 0 )
58         {
59            rColor = 255 * ( ( y / checkSize ) % 2 );
60            bColor = 255 * ( 1 - ( ( y / checkSize ) % 2 ) );
61         }
62         else
63         {
64            bColor = 255 * ( ( y / checkSize ) % 2 );
65            rColor = 255 * ( 1 - ( ( y / checkSize ) % 2 ) );
66         }
67
68         pixels[(y * height + x) * 3] = rColor;
69         pixels[(y * height + x) * 3 + 1] = 0;
70         pixels[(y * height + x) * 3 + 2] = bColor;
71      }
72
73   return pixels;
74}
75
76///
77// Create a mipmapped 2D texture image
78//
79GLuint CreateTexture2D( )
80{
81   // Texture object handle
82   GLuint textureId;
83   int    width = 256,
84          height = 256;
85   GLubyte *pixels;
86
87   pixels = GenCheckImage( width, height, 64 );
88   if ( pixels == NULL )
89      return 0;
90
91   // Generate a texture object
92   glGenTextures ( 1, &textureId );
93
94   // Bind the texture object
95   glBindTexture ( GL_TEXTURE_2D, textureId );
96
97   // Load mipmap level 0
98   glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGB, width, height,
99                  0, GL_RGB, GL_UNSIGNED_BYTE, pixels );
100
101   // Set the filtering mode
102   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
103   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
104
105   return textureId;
106
107}
108
109
110///
111// Initialize the shader and program object
112//
113int Init ( ESContext *esContext )
114{
115   UserData *userData = esContext->userData;
116   GLbyte vShaderStr[] =
117      "uniform float u_offset;      \n"
118      "attribute vec4 a_position;   \n"
119      "attribute vec2 a_texCoord;   \n"
120      "varying vec2 v_texCoord;     \n"
121      "void main()                  \n"
122      "{                            \n"
123      "   gl_Position = a_position; \n"
124      "   gl_Position.x += u_offset;\n"
125      "   v_texCoord = a_texCoord;  \n"
126      "}                            \n";
127
128   GLbyte fShaderStr[] =
129      "precision mediump float;                            \n"
130      "varying vec2 v_texCoord;                            \n"
131      "uniform sampler2D s_texture;                        \n"
132      "void main()                                         \n"
133      "{                                                   \n"
134      "  gl_FragColor = texture2D( s_texture, v_texCoord );\n"
135      "}                                                   \n";
136
137   // Load the shaders and get a linked program object
138   userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
139
140   // Get the attribute locations
141   userData->positionLoc = glGetAttribLocation ( userData->programObject, "a_position" );
142   userData->texCoordLoc = glGetAttribLocation ( userData->programObject, "a_texCoord" );
143
144   // Get the sampler location
145   userData->samplerLoc = glGetUniformLocation ( userData->programObject, "s_texture" );
146
147   // Get the offset location
148   userData->offsetLoc = glGetUniformLocation( userData->programObject, "u_offset" );
149
150   // Load the texture
151   userData->textureId = CreateTexture2D ();
152
153   glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
154   return TRUE;
155}
156
157///
158// Draw a triangle using the shader pair created in Init()
159//
160void Draw ( ESContext *esContext )
161{
162   UserData *userData = esContext->userData;
163   GLfloat vVertices[] = { -0.3f,  0.3f, 0.0f, 1.0f,  // Position 0
164                           -1.0f,  -1.0f,              // TexCoord 0
165                           -0.3f, -0.3f, 0.0f, 1.0f, // Position 1
166                           -1.0f,  2.0f,              // TexCoord 1
167                            0.3f, -0.3f, 0.0f, 1.0f, // Position 2
168                            2.0f,  2.0f,              // TexCoord 2
169                            0.3f,  0.3f, 0.0f, 1.0f,  // Position 3
170                            2.0f,  -1.0f               // TexCoord 3
171                         };
172   GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
173
174   // Set the viewport
175   glViewport ( 0, 0, esContext->width, esContext->height );
176
177   // Clear the color buffer
178   glClear ( GL_COLOR_BUFFER_BIT );
179
180   // Use the program object
181   glUseProgram ( userData->programObject );
182
183   // Load the vertex position
184   glVertexAttribPointer ( userData->positionLoc, 4, GL_FLOAT,
185                           GL_FALSE, 6 * sizeof(GLfloat), vVertices );
186   // Load the texture coordinate
187   glVertexAttribPointer ( userData->texCoordLoc, 2, GL_FLOAT,
188                           GL_FALSE, 6 * sizeof(GLfloat), &vVertices[4] );
189
190   glEnableVertexAttribArray ( userData->positionLoc );
191   glEnableVertexAttribArray ( userData->texCoordLoc );
192
193   // Bind the texture
194   glActiveTexture ( GL_TEXTURE0 );
195   glBindTexture ( GL_TEXTURE_2D, userData->textureId );
196
197   // Set the sampler texture unit to 0
198   glUniform1i ( userData->samplerLoc, 0 );
199
200   // Draw quad with repeat wrap mode
201   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
202   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
203   glUniform1f ( userData->offsetLoc, -0.7f );
204   glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
205
206   // Draw quad with clamp to edge wrap mode
207   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
208   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
209   glUniform1f ( userData->offsetLoc, 0.0f );
210   glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
211
212   // Draw quad with mirrored repeat
213   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_MIRRORED_REPEAT );
214   glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_MIRRORED_REPEAT );
215   glUniform1f ( userData->offsetLoc, 0.7f );
216   glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
217
218   eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
219}
220
221///
222// Cleanup
223//
224void ShutDown ( ESContext *esContext )
225{
226   UserData *userData = esContext->userData;
227
228   // Delete texture object
229   glDeleteTextures ( 1, &userData->textureId );
230
231   // Delete program object
232   glDeleteProgram ( userData->programObject );
233}
234
235
236int main ( int argc, char *argv[] )
237{
238   ESContext esContext;
239   UserData  userData;
240
241   esInitContext ( &esContext );
242   esContext.userData = &userData;
243
244   esCreateWindow ( &esContext, TEXT("Texture Wrap"), 640, 480, ES_WINDOW_RGB );
245
246   if ( !Init ( &esContext ) )
247      return 0;
248
249   esRegisterDrawFunc ( &esContext, Draw );
250
251   esMainLoop ( &esContext );
252
253   ShutDown ( &esContext );
254}
255