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
|
/*******************************************************************
* *
* Using SDL With OpenGL *
* *
* Tutorial by Kyle Foley (sdw) *
* *
* http://gpwiki.org/index.php/SDL:Tutorials:Using_SDL_with_OpenGL *
* *
*******************************************************************/
/*
THIS WORK, INCLUDING THE SOURCE CODE, DOCUMENTATION
AND RELATED MEDIA AND DATA, IS PLACED INTO THE PUBLIC DOMAIN.
THE ORIGINAL AUTHOR IS KYLE FOLEY.
THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY
OF ANY KIND, NOT EVEN THE IMPLIED WARRANTY OF
MERCHANTABILITY. THE AUTHOR OF THIS SOFTWARE,
ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE
RESULTING FROM THE USE, MODIFICATION, OR
REDISTRIBUTION OF THIS SOFTWARE.
*/
#if !EMSCRIPTEN
#define USE_GLEW 1
#endif
#if USE_GLEW
#include "GL/glew.h"
#endif
#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#if !USE_GLEW
#include "SDL/SDL_opengl.h"
#endif
#include <stdio.h>
#include <string.h>
#include <assert.h>
void shaders() {
#if USE_GLEW
glewInit();
#endif
GLint ok;
const char *vertexShader = "void main(void) \n"
"{ \n"
" gl_Position = ftransform(); \n"
" gl_TexCoord[0] = gl_MultiTexCoord0; \n"
" gl_FrontColor = gl_Color; \n"
"} \n";
const char *fragmentShader = "uniform sampler2D tex0; \n"
"void main(void) \n"
"{ \n"
" gl_FragColor = gl_Color * texture2D(tex0, gl_TexCoord[0].xy); \n"
"} \n";
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vs, 1, &vertexShader, NULL);
glCompileShader(vs);
glGetShaderiv(vs, GL_COMPILE_STATUS, &ok);
assert(ok);
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fs, 1, &fragmentShader, NULL);
glCompileShader(fs);
glGetShaderiv(fs, GL_COMPILE_STATUS, &ok);
assert(ok);
GLuint program = glCreateProgram();
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &ok);
assert(ok);
glUseProgram(program);
{
// Also, check getting the error log
const char *fakeVertexShader = "atbute ve4 blarg; ### AAA\n";
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vs, 1, &fakeVertexShader, NULL);
glCompileShader(vs);
glGetShaderiv(vs, GL_COMPILE_STATUS, &ok);
assert(!ok);
GLint infoLen = 0;
glGetShaderiv(vs, GL_INFO_LOG_LENGTH, &infoLen);
assert(infoLen > 1);
}
}
int main(int argc, char *argv[])
{
SDL_Surface *screen;
// Slightly different SDL initialization
if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) {
printf("Unable to initialize SDL: %s\n", SDL_GetError());
return 1;
}
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); // *new*
screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL ); // *changed*
if ( !screen ) {
printf("Unable to set video mode: %s\n", SDL_GetError());
return 1;
}
// Set the OpenGL state after creating the context with SDL_SetVideoMode
glClearColor( 0, 0, 0, 0 );
#if !EMSCRIPTEN
glEnable( GL_TEXTURE_2D ); // Need this to display a texture XXX unnecessary in OpenGL ES 2.0/WebGL
#endif
glViewport( 0, 0, 640, 480 );
glMatrixMode( GL_PROJECTION );
GLfloat matrixData[] = { 2.0/640, 0, 0, 0,
0, -2.0/480, 0, 0,
0, 0, -1, 0,
-1, 1, 0, 1 };
glLoadMatrixf(matrixData); // test loadmatrix
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
// Load the OpenGL texture
GLuint texture; // Texture object handle
// Have OpenGL generate a texture object handle for us
glGenTextures( 1, &texture );
// Bind the texture object
glBindTexture( GL_TEXTURE_2D, texture );
// Set the texture's stretching properties
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
int w = 256, h = 256;
GLushort *pixels = (GLushort*)malloc(w*h*2);
for (int x = 0; x < w; x++)
for (int y = 0; y < h; y++)
pixels[w*y + x] = ((x*32)/w) | ((((w-x)*(h-y)*64)/(w*h)) << 5) | (((y*32)/h) << 11);
// Edit the texture object's image data using the information SDL_Surface gives us
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, w, h, 0,
GL_RGB, GL_UNSIGNED_SHORT_5_6_5, pixels );
// Clear the screen before drawing
glClear( GL_COLOR_BUFFER_BIT );
shaders();
// Bind the texture to which subsequent calls refer to
glBindTexture( GL_TEXTURE_2D, texture );
// Use clientside vertex pointers to render two items
GLfloat vertexData[] = { 0, 0, 10, 10, // texture2, position2
1, 0, 300, 10,
1, 1, 300, 128,
0, 1, 10, 128,
0, 0.5, 410, 10,
1, 0.5, 600, 10,
1, 1, 630, 200,
0.5, 1, 310, 250,
0, 0, 100, 300,
1, 0, 300, 300,
1, 1, 300, 400,
0, 1, 100, 400 };
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 4*4, &vertexData[0]);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(2, GL_FLOAT, 4*4, &vertexData[2]);
glDrawArrays(GL_QUADS, 0, 12);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
SDL_GL_SwapBuffers();
#if !EMSCRIPTEN
// Wait for 3 seconds to give us a chance to see the image
SDL_Delay(3000);
#endif
// Now we can delete the OpenGL texture and close down SDL
glDeleteTextures( 1, &texture );
SDL_Quit();
return 0;
}
|
