Add a geometry shader example

6 files changed, 338 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 55fe9418..c04f81ea 100644
--- a/configure.ac
+++ b/configure.ac
@@ -224,6 +224,7 @@ AC_OUTPUT([
 	src/fp/Makefile
 	src/fpglsl/Makefile
 	src/glsl/Makefile
+	src/gs/Makefile
 	src/images/Makefile
 	src/objviewer/Makefile
 	src/osdemos/Makefile
diff --git a/src/Makefile.am b/src/Makefile.am
index d45b95ae..a9f04522 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -29,6 +29,7 @@ SUBDIRS = \
 	fp \
 	fpglsl \
 	glsl \
+        gs \
 	images \
 	objviewer \
 	osdemos \
diff --git a/src/gs/Makefile.am b/src/gs/Makefile.am
new file mode 100644
index 00000000..f5151f26
--- /dev/null
+++ b/src/gs/Makefile.am
@@ -0,0 +1,15 @@
+AM_CFLAGS = \
+	$(DEMO_CFLAGS) \
+	$(GLUT_CFLAGS) \
+	-I$(top_srcdir)/src/util
+AM_LDFLAGS = \
+	$(DEMO_LIBS) \
+	$(GLUT_LIBS)
+
+if HAVE_GLUT
+noinst_PROGRAMS = \
+	gs-tri
+endif
+
+EXTRA_DIST = \
+	basic.glsl
diff --git a/src/gs/SConscript b/src/gs/SConscript
new file mode 100644
index 00000000..321e619e
--- /dev/null
+++ b/src/gs/SConscript
@@ -0,0 +1,13 @@
+Import('env')
+
+if not env['GLUT']:
+    Return()
+
+env = env.Clone()
+
+env.Prepend(LIBS = ['$GLUT_LIB'])
+
+env.Program(
+        target = 'gs-tri',
+        source = ['gs-tri.c'],
+    )
diff --git a/src/gs/basic.glsl b/src/gs/basic.glsl
new file mode 100644
index 00000000..256a1e6f
--- /dev/null
+++ b/src/gs/basic.glsl
@@ -0,0 +1,16 @@
+#version 120
+#extension GL_ARB_geometry_shader4 : enable
+
+const int KernelSize = 9;
+
+void main()
+{
+  for(int i = 0; i < gl_VerticesIn; ++i)
+  {
+    gl_FrontColor = gl_FrontColorIn[i];
+    gl_BackColor = gl_BackColorIn[i];
+    gl_Position = gl_PositionIn[i];
+    EmitVertex();
+  }
+  EndPrimitive();
+}
diff --git a/src/gs/gs-tri.c b/src/gs/gs-tri.c
new file mode 100644
index 00000000..c33454c1
--- /dev/null
+++ b/src/gs/gs-tri.c
@@ -0,0 +1,292 @@
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#define GL_GLEXT_PROTOTYPES
+#include <GL/glut.h>
+#include <GL/glext.h>
+
+static const char *filename = NULL;
+static GLuint nr_steps = 0;
+
+static GLuint fragShader;
+static GLuint vertShader;
+static GLuint geoShader;
+static GLuint program;
+
+static void usage( char *name )
+{
+   fprintf(stderr, "usage: %s [ options ] shader_filename\n", name);
+   fprintf(stderr, "\n" );
+   fprintf(stderr, "options:\n" );
+   fprintf(stderr, "    -f     flat shaded\n" );
+   fprintf(stderr, "    -nNr  subdivision steps\n" );
+}
+
+
+static void load_and_compile_shader(GLuint shader, const char *text)
+{
+   GLint stat;
+
+   glShaderSource(shader, 1, (const GLchar **) &text, NULL);
+   glCompileShader(shader);
+   glGetShaderiv(shader, GL_COMPILE_STATUS, &stat);
+   if (!stat) {
+      GLchar log[1000];
+      GLsizei len;
+      glGetShaderInfoLog(shader, 1000, &len, log);
+      fprintf(stderr, "gp: problem compiling shader:\n%s\n", log);
+      exit(1);
+   }
+}
+
+static void read_shader(GLuint shader, const char *filename)
+{
+   const int max = 100*1000;
+   int n;
+   char *buffer = (char*) malloc(max);
+   FILE *f = fopen(filename, "r");
+   if (!f) {
+      fprintf(stderr, "gp: Unable to open shader file %s\n", filename);
+      exit(1);
+   }
+
+   n = fread(buffer, 1, max, f);
+   printf("gp: read %d bytes from shader file %s\n", n, filename);
+   if (n > 0) {
+      buffer[n] = 0;
+      load_and_compile_shader(shader, buffer);
+   }
+
+   fclose(f);
+   free(buffer);
+}
+
+static void check_link(GLuint prog)
+{
+   GLint stat;
+   glGetProgramiv(prog, GL_LINK_STATUS, &stat);
+   if (!stat) {
+      GLchar log[1000];
+      GLsizei len;
+      glGetProgramInfoLog(prog, 1000, &len, log);
+      fprintf(stderr, "Linker error:\n%s\n", log);
+   }
+}
+
+static void prepare_shaders(void)
+{
+   static const char *fragShaderText =
+      "void main() {\n"
+      "    gl_FragColor = gl_Color;\n"
+      "}\n";
+   static const char *vertShaderText =
+      "void main() {\n"
+      "   gl_FrontColor = gl_Color;\n"
+      "   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+      "}\n";
+   static const char *geoShaderText =
+      "#version 120\n"
+      "#extension GL_ARB_geometry_shader4 : enable\n"
+      "void main()\n"
+      "{\n"
+      "  for(int i = 0; i < gl_VerticesIn; ++i)\n"
+      "  {\n"
+      "    gl_FrontColor = gl_FrontColorIn[i];\n"
+      "    gl_Position = gl_PositionIn[i];\n"
+      "    EmitVertex();\n"
+      "  }\n"
+      "}\n";
+   fragShader = glCreateShader(GL_FRAGMENT_SHADER);
+   load_and_compile_shader(fragShader, fragShaderText);
+
+   vertShader = glCreateShader(GL_VERTEX_SHADER);
+   load_and_compile_shader(vertShader, vertShaderText);
+
+   geoShader = glCreateShader(GL_GEOMETRY_SHADER_ARB);
+   if (filename)
+      read_shader(geoShader, filename);
+   else
+      load_and_compile_shader(geoShader,
+                              geoShaderText);
+
+   program = glCreateProgram();
+   glAttachShader(program, vertShader);
+   glAttachShader(program, geoShader);
+   glAttachShader(program, fragShader);
+
+   glProgramParameteriARB(program, GL_GEOMETRY_INPUT_TYPE_ARB, GL_TRIANGLES);
+   glProgramParameteriARB(program, GL_GEOMETRY_OUTPUT_TYPE_ARB,
+                          GL_TRIANGLE_STRIP);
+
+   {
+      int temp;
+      glGetIntegerv(GL_MAX_GEOMETRY_OUTPUT_VERTICES_ARB,&temp);
+      glProgramParameteriARB(program,GL_GEOMETRY_VERTICES_OUT_ARB,temp);
+   }
+
+   glLinkProgram(program);
+   check_link(program);
+   glUseProgram(program);
+}
+
+static void args(int argc, char *argv[])
+{
+   GLint i;
+
+   for (i = 1; i < argc; i++) {
+      if (strncmp(argv[i], "-n", 2) == 0) {
+	 nr_steps = atoi((argv[i]) + 2);
+      }
+      else if (strcmp(argv[i], "-f") == 0) {
+	 glShadeModel(GL_FLAT);
+      }
+      else if (i == argc - 1) {
+	 filename = argv[i];
+      }
+      else {
+	 usage(argv[0]);
+	 exit(1);
+      }
+   }
+
+   if (!filename) {
+      usage(argv[0]);
+      exit(1);
+   }
+}
+
+
+
+
+union vert {
+   struct {
+      GLfloat color[3];
+      GLfloat pos[3];
+   } v;
+   GLfloat f[6];
+};
+
+static void make_midpoint( union vert *out,
+			   const union vert *v0,
+			   const union vert *v1)
+{
+   int i;
+   for (i = 0; i < 6; i++)
+      out->f[i] = v0->f[i] + .5 * (v1->f[i] - v0->f[i]);
+}
+
+static void subdiv( union vert *v0,
+		    union vert *v1,
+		    union vert *v2,
+		    GLuint depth )
+{
+   if (depth == 0) {
+      glColor3fv(v0->v.color);
+      glVertex3fv(v0->v.pos);
+      glColor3fv(v1->v.color);
+      glVertex3fv(v1->v.pos);
+      glColor3fv(v2->v.color);
+      glVertex3fv(v2->v.pos);
+   }
+   else {
+      union vert m[3];
+
+      make_midpoint(&m[0], v0, v1);
+      make_midpoint(&m[1], v1, v2);
+      make_midpoint(&m[2], v2, v0);
+
+      subdiv(&m[0], &m[2], v0, depth-1);
+      subdiv(&m[1], &m[0], v1, depth-1);
+      subdiv(&m[2], &m[1], v2, depth-1);
+      subdiv(&m[0], &m[1], &m[2], depth-1);
+   }
+}
+
+/** Assignment */
+#define ASSIGN_3V( V, V0, V1, V2 )  \
+do {                                \
+    V[0] = V0;                      \
+    V[1] = V1;                      \
+    V[2] = V2;                      \
+} while(0)
+
+static void Display( void )
+{
+   glClearColor(0.3, 0.3, 0.3, 1);
+   glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
+
+   glUseProgram(program);
+
+   glBegin(GL_TRIANGLES);
+
+
+   {
+      union vert v[3];
+
+      ASSIGN_3V(v[0].v.color, 0,0,1);
+      ASSIGN_3V(v[0].v.pos,  0.9, -0.9, 0.0);
+      ASSIGN_3V(v[1].v.color, 1,0,0);
+      ASSIGN_3V(v[1].v.pos, 0.9, 0.9, 0.0);
+      ASSIGN_3V(v[2].v.color, 0,1,0);
+      ASSIGN_3V(v[2].v.pos, -0.9, 0, 0.0);
+
+      subdiv(&v[0], &v[1], &v[2], nr_steps);
+   }
+
+   glEnd();
+
+
+   glFlush();
+}
+
+
+static void Reshape( int width, int height )
+{
+   glViewport( 0, 0, width, height );
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
+   glMatrixMode( GL_MODELVIEW );
+   glLoadIdentity();
+   /*glTranslatef( 0.0, 0.0, -15.0 );*/
+}
+
+
+static void CleanUp(void)
+{
+   glDeleteShader(fragShader);
+   glDeleteShader(vertShader);
+   glDeleteProgram(program);
+}
+
+static void Key( unsigned char key, int x, int y )
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+      case 27:
+         CleanUp();
+         exit(0);
+         break;
+   }
+   glutPostRedisplay();
+}
+
+int main( int argc, char *argv[] )
+{
+   glutInit( &argc, argv );
+   glutInitWindowPosition( 0, 0 );
+   glutInitWindowSize( 250, 250 );
+   glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH );
+   glutCreateWindow(argv[0]);
+   glutReshapeFunc( Reshape );
+   glutKeyboardFunc( Key );
+   glutDisplayFunc( Display );
+   args( argc, argv );
+   prepare_shaders();
+   glutMainLoop();
+   return 0;
+}