1 /**
2 * Draw two quads, one using only a vertex shader, the other only with a
3 * fragment shader. They should appear the same.
4 * 17 Dec 2008
5 * Brian Paul
6 */
7
8
9 #include <assert.h>
10 #include <string.h>
11 #include <stdio.h>
12 #include <stdlib.h>
13 #include <math.h>
14 #include <glad/glad.h>
15 #include "glut_wrap.h"
16 #include "shaderutil.h"
17
18
19 static char *FragProgFile = NULL;
20 static char *VertProgFile = NULL;
21 static GLuint FragShader;
22 static GLuint VertShader;
23 static GLuint VertProgram; /* w/out vertex shader */
24 static GLuint FragProgram; /* w/out fragment shader */
25 static GLint Win = 0;
26
27
28 static void
DrawQuadColor(void)29 DrawQuadColor(void)
30 {
31 glBegin(GL_QUADS);
32 glColor3f(1, 0, 0); glVertex2f(-1, -1);
33 glColor3f(0, 1, 0); glVertex2f( 1, -1);
34 glColor3f(0, 0, 1); glVertex2f( 1, 1);
35 glColor3f(1, 0, 1); glVertex2f(-1, 1);
36 glEnd();
37 }
38
39
40 /** as above, but specify color via texcoords */
41 static void
DrawQuadTex(void)42 DrawQuadTex(void)
43 {
44 glBegin(GL_QUADS);
45 glTexCoord3f(1, 0, 0); glVertex2f(-1, -1);
46 glTexCoord3f(0, 1, 0); glVertex2f( 1, -1);
47 glTexCoord3f(0, 0, 1); glVertex2f( 1, 1);
48 glTexCoord3f(1, 0, 1); glVertex2f(-1, 1);
49 glEnd();
50 }
51
52
53 static void
Redisplay(void)54 Redisplay(void)
55 {
56 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
57
58 /* render with vertex shader only */
59 glUseProgram(VertProgram);
60 glPushMatrix();
61 glTranslatef(-1.5, 0, 0);
62 DrawQuadTex();
63 glPopMatrix();
64
65 /* render with fragment shader only */
66 glUseProgram(FragProgram);
67 glPushMatrix();
68 glTranslatef(+1.5, 0, 0);
69 DrawQuadColor();
70 glPopMatrix();
71
72 glutSwapBuffers();
73 }
74
75
76 static void
Reshape(int width,int height)77 Reshape(int width, int height)
78 {
79 glViewport(0, 0, width, height);
80 glMatrixMode(GL_PROJECTION);
81 glLoadIdentity();
82 glOrtho(-4, 4, -2, 2, -1, 1);
83 glMatrixMode(GL_MODELVIEW);
84 glLoadIdentity();
85 }
86
87
88 static void
CleanUp(void)89 CleanUp(void)
90 {
91 glDeleteShader(FragShader);
92 glDeleteShader(VertShader);
93 glDeleteProgram(VertProgram);
94 glDeleteProgram(FragProgram);
95 glutDestroyWindow(Win);
96 }
97
98
99 static void
Key(unsigned char key,int x,int y)100 Key(unsigned char key, int x, int y)
101 {
102 (void) x;
103 (void) y;
104 switch(key) {
105 case 27:
106 CleanUp();
107 exit(0);
108 break;
109 }
110 glutPostRedisplay();
111 }
112
113
114 static void
Init(void)115 Init(void)
116 {
117 static const char *fragShaderText =
118 "void main() {\n"
119 " gl_FragColor = gl_Color;\n"
120 "}\n";
121 static const char *vertShaderText =
122 "void main() {\n"
123 " gl_Position = ftransform();\n"
124 " gl_FrontColor = gl_MultiTexCoord0;\n" /* see DrawQuadTex() */
125 "}\n";
126
127 if (!ShadersSupported())
128 exit(1);
129
130 if (FragProgFile)
131 FragShader = CompileShaderFile(GL_FRAGMENT_SHADER, FragProgFile);
132 else
133 FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
134
135 if (VertProgFile)
136 VertShader = CompileShaderFile(GL_VERTEX_SHADER, VertProgFile);
137 else
138 VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
139
140 VertProgram = LinkShaders(VertShader, 0);
141 FragProgram = LinkShaders(0, FragShader);
142
143 glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
144 glEnable(GL_DEPTH_TEST);
145
146 printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
147
148 assert(glIsProgram(VertProgram));
149 assert(glIsProgram(FragProgram));
150 assert(glIsShader(FragShader));
151 assert(glIsShader(VertShader));
152
153 glColor3f(1, 0, 0);
154 }
155
156
157 static void
ParseOptions(int argc,char * argv[])158 ParseOptions(int argc, char *argv[])
159 {
160 int i;
161 for (i = 1; i < argc; i++) {
162 if (strcmp(argv[i], "-fs") == 0) {
163 FragProgFile = argv[i+1];
164 }
165 else if (strcmp(argv[i], "-vs") == 0) {
166 VertProgFile = argv[i+1];
167 }
168 }
169 }
170
171
172 int
main(int argc,char * argv[])173 main(int argc, char *argv[])
174 {
175 glutInit(&argc, argv);
176 glutInitWindowSize(400, 200);
177 glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
178 Win = glutCreateWindow(argv[0]);
179 gladLoadGL();
180 glutReshapeFunc(Reshape);
181 glutKeyboardFunc(Key);
182 glutDisplayFunc(Redisplay);
183 ParseOptions(argc, argv);
184 Init();
185 glutMainLoop();
186 return 0;
187 }
188