1 files changed, 192 insertions, 0 deletions
diff --git a/src/tests/front-back-modes.c b/src/tests/front-back-modes.c
new file mode 100644
index 0000000..9e956f7
--- /dev/null
+++ b/src/tests/front-back-modes.c
@@ -0,0 +1,192 @@
+/**
+ * Test glPolygonMode w/ different front/back face modes.
+ *
+ * The left half of the window draws a torus with different front/back
+ * polygon modes.
+ *
+ * The right half of the windows tries to draw the same thing, but with
+ * a different approach:
+ *   glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+ *   glEnable(GL_CULL_FACE);
+ *   glCullFace(GL_FRONT);
+ *   draw_object();
+ *   glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+ *   glEnable(GL_CULL_FACE);
+ *   glCullFace(GL_BACK);
+ *   draw_object();
+ *
+ * The outcome is often the same, but not always (turn on blending with 'b').
+ *
+ * Brian Paul
+ * 2 Feb 2016
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include "glut_wrap.h"
+
+static int Win;
+static int WinWidth = 800, WinHeight = 400;
+static GLfloat Xrot = 0;
+static GLboolean Anim = GL_TRUE;
+static double t0;
+static GLboolean Blend = GL_TRUE;
+
+
+static void
+Idle(void)
+{
+   double t1 = glutGet(GLUT_ELAPSED_TIME) / 1000.0;
+   Xrot += (t1 - t0) * 20;  /* 20 degrees per second */
+   t0 = t1;
+   glutPostRedisplay();
+}
+
+
+static void
+Draw(void)
+{
+   int hw = WinWidth / 2;
+
+   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+   if (Blend) {
+      glEnable(GL_BLEND);
+      glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+      glBlendFunc(GL_ONE, GL_ONE);
+   }
+   else {
+      glDisable(GL_BLEND);
+   }
+
+   glPushMatrix();
+   glRotatef(Xrot, 1, 0, 0);
+
+   /* draw left half */
+   glViewport(0, 0, hw, WinHeight);
+
+   glPolygonMode(GL_FRONT, GL_LINE);
+   glPolygonMode(GL_BACK, GL_FILL);
+   glDisable(GL_CULL_FACE);
+   glutSolidTorus(0.75, 2.0, 10, 20);
+
+   /* draw right half */
+   glViewport(hw, 0, WinWidth - hw, WinHeight);
+
+   /* draw back faces */
+   glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+   glEnable(GL_CULL_FACE);
+   glCullFace(GL_FRONT);
+   glutSolidTorus(0.75, 2.0, 10, 20);
+
+   /* draw front faces */
+   glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+   glEnable(GL_CULL_FACE);
+   glCullFace(GL_BACK);
+   glutSolidTorus(0.75, 2.0, 10, 20);
+
+   glPopMatrix();
+
+   glutSwapBuffers();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+   WinWidth = width;
+   WinHeight = height;
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glFrustum(-1.0, 1.0, -1.0, 1.0, 3.0, 25.0);
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+   glTranslatef(0.0, 0.0, -10.0);
+   glutPostRedisplay();
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+   case 'a':
+      Anim = !Anim;
+      if (Anim) {
+         t0 = glutGet(GLUT_ELAPSED_TIME) / 1000.0;
+         glutIdleFunc(Idle);
+      }
+      else
+         glutIdleFunc(NULL);
+      break;
+   case 'b':
+      Blend = !Blend;
+      break;
+   case 27:
+      glutDestroyWindow(Win);
+      exit(0);
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+SpecialKey(int key, int x, int y)
+{
+   const GLfloat step = 3.0;
+   (void) x;
+   (void) y;
+   switch (key) {
+   case GLUT_KEY_UP:
+      Xrot -= step;
+      break;
+   case GLUT_KEY_DOWN:
+      Xrot += step;
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+Init(void)
+{
+   static const float yellow[4] = {1, 1, 0, 0.5};
+   static const float blue[4] = {0.2, 0.2, 1, 0.5};
+   static const float gray[4] = {0.2, 0.2, 0.2, 1.0};
+
+   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, gray);
+   glMaterialfv(GL_FRONT, GL_DIFFUSE, yellow);
+   glMaterialfv(GL_BACK, GL_DIFFUSE, blue);
+   glEnable(GL_DEPTH_TEST);
+   glEnable(GL_LIGHTING);
+   glEnable(GL_LIGHT0);
+   glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 1);
+   glShadeModel(GL_FLAT);
+
+   glClearColor(0.25, 0.25, 0.25, 1.0);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+   glutInit(&argc, argv);
+   glutInitWindowSize(WinWidth, WinHeight);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
+   Win = glutCreateWindow(argv[0]);
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutSpecialFunc(SpecialKey);
+   glutDisplayFunc(Draw);
+   if (Anim)
+      glutIdleFunc(Idle);
+   Init();
+   glutMainLoop();
+   return 0;
+}