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/**
* Draw two quads, one using only a vertex shader, the other only with a
* fragment shader. They should appear the same.
* 17 Dec 2008
* Brian Paul
*/
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glew.h>
#include <GL/glut.h>
#include "shaderutil.h"
static char *FragProgFile = NULL;
static char *VertProgFile = NULL;
static GLuint FragShader;
static GLuint VertShader;
static GLuint VertProgram; /* w/out vertex shader */
static GLuint FragProgram; /* w/out fragment shader */
static GLint Win = 0;
static void
DrawQuadColor(void)
{
glBegin(GL_QUADS);
glColor3f(1, 0, 0); glVertex2f(-1, -1);
glColor3f(0, 1, 0); glVertex2f( 1, -1);
glColor3f(0, 0, 1); glVertex2f( 1, 1);
glColor3f(1, 0, 1); glVertex2f(-1, 1);
glEnd();
}
/** as above, but specify color via texcoords */
static void
DrawQuadTex(void)
{
glBegin(GL_QUADS);
glTexCoord3f(1, 0, 0); glVertex2f(-1, -1);
glTexCoord3f(0, 1, 0); glVertex2f( 1, -1);
glTexCoord3f(0, 0, 1); glVertex2f( 1, 1);
glTexCoord3f(1, 0, 1); glVertex2f(-1, 1);
glEnd();
}
static void
Redisplay(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
/* render with vertex shader only */
glUseProgram(VertProgram);
glPushMatrix();
glTranslatef(-1.5, 0, 0);
DrawQuadTex();
glPopMatrix();
/* render with fragment shader only */
glUseProgram(FragProgram);
glPushMatrix();
glTranslatef(+1.5, 0, 0);
DrawQuadColor();
glPopMatrix();
glutSwapBuffers();
}
static void
Reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-4, 4, -2, 2, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
static void
CleanUp(void)
{
glDeleteShader(FragShader);
glDeleteShader(VertShader);
glDeleteProgram(VertProgram);
glDeleteProgram(FragProgram);
glutDestroyWindow(Win);
}
static void
Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
switch(key) {
case 27:
CleanUp();
exit(0);
break;
}
glutPostRedisplay();
}
static void
Init(void)
{
static const char *fragShaderText =
"void main() {\n"
" gl_FragColor = gl_Color;\n"
"}\n";
static const char *vertShaderText =
"void main() {\n"
" gl_Position = ftransform();\n"
" gl_FrontColor = gl_MultiTexCoord0;\n" /* see DrawQuadTex() */
"}\n";
if (!ShadersSupported())
exit(1);
if (FragProgFile)
FragShader = CompileShaderFile(GL_FRAGMENT_SHADER, FragProgFile);
else
FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
if (VertProgFile)
VertShader = CompileShaderFile(GL_VERTEX_SHADER, VertProgFile);
else
VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
VertProgram = LinkShaders(VertShader, 0);
FragProgram = LinkShaders(0, FragShader);
glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
glEnable(GL_DEPTH_TEST);
printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
assert(glIsProgram(VertProgram));
assert(glIsProgram(FragProgram));
assert(glIsShader(FragShader));
assert(glIsShader(VertShader));
glColor3f(1, 0, 0);
}
static void
ParseOptions(int argc, char *argv[])
{
int i;
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-fs") == 0) {
FragProgFile = argv[i+1];
}
else if (strcmp(argv[i], "-vs") == 0) {
VertProgFile = argv[i+1];
}
}
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(400, 200);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
Win = glutCreateWindow(argv[0]);
glewInit();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Redisplay);
ParseOptions(argc, argv);
Init();
glutMainLoop();
return 0;
}
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