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
|
/*******************************************************************
* *
* 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 0
#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>
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_MODELVIEW );
glLoadIdentity();
// Clear the screen before drawing
glClear( GL_COLOR_BUFFER_BIT );
typedef struct Vertex {
GLfloat x;
GLfloat y;
} Vertex;
typedef struct Color {
GLubyte r;
GLubyte g;
GLubyte b;
GLubyte a;
} Color;
typedef struct Type1 {
Vertex location;
Color color;
} Type1;
typedef struct Type2 {
GLuint unused1;
Vertex location;
GLfloat unused2;
Color color;
} Type2;
Type1 first[3] = {
{{-1.0, 0.0}, {0xFF, 0x00, 0x00, 0xFF}},
{{ 0.0, 1.0}, {0x00, 0xFF, 0x00, 0xFF}},
{{ 1.0, 0.0}, {0x00, 0x00, 0xFF, 0xFF}}
};
Type2 second[3] = {
{0.0, {-1.0, 0.0}, 0.0, {0xFF, 0x00, 0x00, 0xFF}},
{0.0, { 1.0, 0.0}, 0.0, {0x00, 0x00, 0xFF, 0xFF}},
{0.0, { 0.0, -1.0}, 0.0, {0x00, 0xFF, 0x00, 0xFF}}};
// make two vbo objects
GLuint vbo[2];
glGenBuffers(2, &vbo[0]);
// load the first into the context
glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
// allocate enough space for 100 vertices
glBufferData(GL_ARRAY_BUFFER, sizeof(Type1)*100, NULL, GL_DYNAMIC_DRAW);
// load the second into the context
glBindBuffer(GL_ARRAY_BUFFER, vbo[1]);
// allocate enough space for 100 vertices
glBufferData(GL_ARRAY_BUFFER, sizeof(Type2)*100, NULL, GL_DYNAMIC_DRAW);
// DRAW
GLbyte * pointer;
// Clear the screen before drawing
glClear( GL_COLOR_BUFFER_BIT );
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
// FIRST
// load the first into the context
glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
// Load actual data in
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Type1)*3, &first[0]);
// point to the buffer's location data
glVertexPointer(2, GL_FLOAT, sizeof(Type1), NULL);
pointer = (GLbyte*)(((GLbyte*)&first[0].color) - ((GLbyte*)&first[0].location));
printf("location = %p\n", pointer);
// point to the buffer's color data
glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(Type1), pointer);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 3);
// SECOND
// load the first into the context
glBindBuffer(GL_ARRAY_BUFFER, vbo[1]);
// Load actual data in
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Type2)*3, &second[0]);
pointer = (GLbyte*)((GLbyte*)&second[0].location - (GLbyte*)&second[0].unused1);
// point to the buffer's location data
printf("location = %p\n", pointer);
glVertexPointer(2, GL_FLOAT, sizeof(Type2), pointer);
pointer = (GLbyte*)((GLbyte*)&second[0].color - (GLbyte*)&second[0].unused1);
// point to the buffer's location data
printf("location = %p\n", pointer);
glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(Type2), pointer);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 3);
glDisableClientState(GL_COLOR_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
SDL_Quit();
return 0;
}
|
