added progs/demos/fragcoord.c - tests gl_FragCoord attribute in fragment shader

Fragment's red/greenb/blue is a function gl_FragCoord.xyz

progs/glsl/Makefile

@@ -16,6 +16,7 @@ PROGS = \
 	convolutions \
 	deriv \
 	identity \
+	fragcoord \
 	mandelbrot \
 	multitex \
 	noise \
@@ -115,6 +116,13 @@ identity: identity.o shaderutil.o
 	$(APP_CC) -I$(INCDIR) $(CFLAGS) $(LDFLAGS) identity.o shaderutil.o $(LIBS) -o $@
 
 
+fragcoord.o: fragcoord.c extfuncs.h shaderutil.h
+	$(CC) -c -I$(INCDIR) $(CFLAGS) fragcoord.c
+
+fragcoord: fragcoord.o shaderutil.o
+	$(CC) -I$(INCDIR) $(CFLAGS) $(LDFLAGS) fragcoord.o shaderutil.o $(LIBS) -o $@
+
+
 mandelbrot.o: mandelbrot.c extfuncs.h shaderutil.h
 	$(APP_CC) -c -I$(INCDIR) $(CFLAGS) mandelbrot.c
 

progs/glsl/fragcoord.c

@@ -0,0 +1,185 @@
+/**
+ * Test GLSL gl_FragCoord fragment program attribute.
+ * Color the quad's fragments according to their window position.
+ *
+ * Brian Paul
+ * 20 Nov 2008
+ */
+
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/gl.h>
+#include <GL/glut.h>
+#include <GL/glext.h>
+#include "extfuncs.h"
+#include "shaderutil.h"
+
+
+static GLint WinWidth = 200, WinHeight = 200;
+static char *FragProgFile = NULL;
+static char *VertProgFile = NULL;
+static GLuint fragShader;
+static GLuint vertShader;
+static GLuint program;
+static GLint win = 0;
+static GLboolean Anim = GL_TRUE;
+static GLfloat PosX = 0.0, PosY = 0.0;
+
+
+static void
+Idle(void)
+{
+   float r = (WinWidth < WinHeight) ? WinWidth : WinHeight;
+   float a = glutGet(GLUT_ELAPSED_TIME) * 0.001;
+   r *= 0.25;
+   PosX = WinWidth / 2 + r * cos(a);
+   PosY = WinHeight / 2 + r * sin(a);
+
+   glutPostRedisplay();
+}
+
+
+static void
+Redisplay(void)
+{
+   glClear(GL_COLOR_BUFFER_BIT);
+
+   glPushMatrix();
+   glTranslatef(PosX, PosY, 0.0);
+#if 0
+   glBegin(GL_POLYGON);
+   glVertex2f(-50, -50);
+   glVertex2f( 50, -50);
+   glVertex2f( 50,  50);
+   glVertex2f(-50,  50);
+   glEnd();
+#else
+   glutSolidSphere(50, 20, 10);
+#endif
+   glPopMatrix();
+
+   glutSwapBuffers();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+   glViewport(0, 0, width, height);
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glOrtho(0, width, 0, height, -55, 55);
+
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+
+   WinWidth = width;
+   WinHeight = height;
+}
+
+
+static void
+CleanUp(void)
+{
+   glDeleteShader_func(fragShader);
+   glDeleteShader_func(vertShader);
+   glDeleteProgram_func(program);
+   glutDestroyWindow(win);
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+  (void) x;
+  (void) y;
+
+   switch(key) {
+   case ' ':
+   case 'a':
+      Anim = !Anim;
+      glutIdleFunc(Anim ? Idle : NULL);
+      break;
+   case 27:
+      CleanUp();
+      exit(0);
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+Init(void)
+{
+   static const char *fragShaderText =
+      "void main() { \n"
+      "   vec4 scale = vec4(.005, 0.005, 0.5, 1.0);\n"
+      "   gl_FragColor = gl_FragCoord * scale; \n"
+      "}\n";
+   static const char *vertShaderText =
+      "void main() {\n"
+      "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+      "}\n";
+
+   if (!ShadersSupported())
+      exit(1);
+
+   GetExtensionFuncs();
+
+   vertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
+   fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
+   program = LinkShaders(vertShader, fragShader);
+
+   glUseProgram_func(program);
+
+   /*assert(glGetError() == 0);*/
+
+   glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
+
+   printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
+
+   assert(glIsProgram_func(program));
+   assert(glIsShader_func(fragShader));
+   assert(glIsShader_func(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);
+   glutInitWindowPosition( 0, 0);
+   glutInitWindowSize(WinWidth, WinHeight);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
+   win = glutCreateWindow(argv[0]);
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutDisplayFunc(Redisplay);
+   ParseOptions(argc, argv);
+   Init();
+   glutIdleFunc(Anim ? Idle : NULL);
+   glutMainLoop();
+   return 0;
+}