linehacks: do stipple, wide, smooth lines with hacks

2 files changed, 332 insertions, 0 deletions

diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
index c8a575a7..ef1a2079 100644
--- a/src/tests/Makefile.am
+++ b/src/tests/Makefile.am
@@ -100,6 +100,7 @@ noinst_PROGRAMS = \
 	invert \
 	jkrahntest \
 	lineclip \
+	linehacks \
 	manytex \
 	mapbufrange \
 	minmag \
@@ -172,6 +173,7 @@ floattex_LDADD = ../util/libutil.la
 fillrate_LDADD = ../util/libutil.la
 invert_LDADD = ../util/libutil.la
 jkrahntest_LDADD = -lX11
+linehacks_LDADD = ../util/libutil.la
 mipmap_limits_LDADD = ../util/libutil.la
 mipmap_view_LDADD = ../util/libutil.la
 sharedtex_LDADD = -lX11
diff --git a/src/tests/linehacks.c b/src/tests/linehacks.c
new file mode 100644
index 00000000..e4d0e16c
--- /dev/null
+++ b/src/tests/linehacks.c
@@ -0,0 +1,330 @@
+/**
+ * Test some hacks to approximate wide lines, AA lines and stippled lines
+ * by drawing the lines multiple times at offsets and stippling with a fragment
+ * shader.
+ *
+ * Brian Paul
+ * June 2011
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/glew.h>
+#include "glut_wrap.h"
+#include "shaderutil.h"
+
+
+static int Win;
+static int WinWidth = 1000, WinHeight = 500;
+static GLboolean Anti = GL_FALSE, Stipple = GL_FALSE;
+static GLfloat LineWidth = 1.0, MaxLineWidth = 3.0;
+static GLuint StippleProgram;
+
+
+/**
+ * Generate a 2D texture stipple pattern from 1D line stipple pattern.
+ * Note: the stipple repeat factor could be implemented by scaling the
+ * texcoords in the frag shader.
+ */
+static GLuint
+LineStippleToTexture(GLushort pattern)
+{
+   GLuint tex, i, j;
+   GLubyte pattern2d[16][16];
+
+   glGenTextures(1, &tex);
+   glBindTexture(GL_TEXTURE_2D, tex);
+
+   for (i = 0; i < 16; i++) {
+      for (j = 0; j < 16; j++) {
+         GLuint ibit = (pattern >> i) & 1;
+         GLuint jbit = (pattern >> j) & 1;
+         pattern2d[i][j] = (ibit | jbit) * 255;
+      }
+   }
+
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+   glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, 16, 16, 0,
+                GL_LUMINANCE, GL_UNSIGNED_BYTE, pattern2d);
+
+   return tex;
+}
+
+
+/** Draw some lines */
+static void
+DrawLines(void)
+{
+   const float r0 = 0.2, r1 = 0.9;
+   float a;
+
+   glBegin(GL_LINES);
+   for (a = 0.0; a < 2.0*M_PI; a += 0.1) {
+      float x0 = r0 * cos(a), y0 = r0 * sin(a);
+      float x1 = r1 * cos(a), y1 = r1 * sin(a);
+      glVertex2f(x0, y0);
+      glVertex2f(x1, y1);
+   }
+   glEnd();
+   glBegin(GL_LINE_LOOP);
+   for (a = 0.0; a <= 2.0*M_PI; a += 0.1) {
+      float x1 = r1 * cos(a), y1 = r1 * sin(a);
+      glVertex2f(x1, y1);
+   }
+   glEnd();
+   glBegin(GL_LINE_LOOP);
+   for (a = 0.0; a <= 2.0*M_PI; a += 0.1) {
+      float x0 = r0 * cos(a), y0 = r0 * sin(a);
+      glVertex2f(x0, y0);
+   }
+   glEnd();
+   glBegin(GL_LINE_LOOP);
+   glVertex2f(-r1, -r1);
+   glVertex2f(+r1, -r1);
+   glVertex2f(+r1, +r1);
+   glVertex2f(-r1, +r1);
+   glEnd();
+}
+
+
+static void
+Draw(void)
+{
+   GLint vpWidth = WinWidth / 2;
+   GLint vpHeight = WinHeight;
+
+   glClear(GL_COLOR_BUFFER_BIT);
+
+   /* draw regular lines */
+   {
+      if (Anti) {
+         glEnable(GL_LINE_SMOOTH);
+         glEnable(GL_BLEND);
+      }
+      if (Stipple)
+         glEnable(GL_LINE_STIPPLE);
+      glLineWidth(LineWidth);
+
+      glViewport(0, 0, vpWidth, vpHeight);
+      glColor3f(1, 1, 1);
+      DrawLines();
+
+      glDisable(GL_LINE_SMOOTH);
+      glDisable(GL_LINE_STIPPLE);
+      glDisable(GL_BLEND);
+      glLineWidth(1.0);
+   }
+
+   /* draw hacked lines */
+   {
+#define ALPHA 0.5
+      static const float offsets_alpha[5][3] = {
+         { 0.0, 0.0, 1.0 },
+#if 0
+         { 1.0, 0.5, ALPHA },
+         { -1.0, -0.5, ALPHA },
+         { -0.5, 1.0, ALPHA },
+         { 0.5, -1.0, ALPHA }
+#else
+         { 1.0, 0.0, ALPHA },
+         { -1.0, 0.0, ALPHA },
+         { 0.0, 1.0, ALPHA },
+         { 0.0, -1.0, ALPHA }
+#endif
+      };
+
+      int passes, pass;
+      float s;
+
+      glViewport(vpWidth, 0, vpWidth, vpHeight);
+
+      if (Anti || LineWidth > 1.5) {
+         passes = 5;
+      }
+      else {
+         passes = 1;
+      }
+      if (Anti) 
+         s = 2.0 * LineWidth / MaxLineWidth;
+      else
+         s = 1.5 * LineWidth / MaxLineWidth;
+
+      if (Stipple) {
+         glUseProgram(StippleProgram);
+      }
+      if (Anti) {
+         glEnable(GL_BLEND);
+      }
+
+      for (pass = 0; pass < passes; pass++) {
+         /* Translate all vertices by small x/y offset */
+         float tx = offsets_alpha[pass][0] / vpWidth * s;
+         float ty = offsets_alpha[pass][1] / vpHeight * s;
+         /* adjust fragment alpha (this could be done in many ways) */
+         glColor4f(1, 1, 1, offsets_alpha[pass][2]);
+
+         glPushMatrix();
+         glTranslatef(tx, ty, 0.0);
+            DrawLines();
+         glPopMatrix();
+      }
+
+      if (1) {
+         /* debug: show the 2D texture / stipple pattern */
+         GLfloat w = 32.0 / (vpWidth);
+         GLfloat h = 32.0 / (vpHeight);
+
+         glColor3f(1, 1, 1);
+         glBegin(GL_QUADS);
+         glVertex2f(0.0, 0.0);
+         glVertex2f(w, 0.0);
+         glVertex2f(w, h);
+         glVertex2f(0.0, h);
+         glEnd();
+      }
+
+      glUseProgram(0);
+      glDisable(GL_BLEND);
+
+   }
+
+   glutSwapBuffers();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+   WinWidth = width;
+   WinHeight = height;
+   glViewport(0, 0, width, height);
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+   case 'a':
+      Anti = !Anti;
+      break;
+   case 's':
+      Stipple = !Stipple;
+      break;
+   case 'w':
+      LineWidth -= 0.25;
+      if (LineWidth < 1.0)
+         LineWidth = 1.0;
+      break;
+   case 'W':
+      LineWidth += 0.25;
+      if (LineWidth > MaxLineWidth)
+         LineWidth = MaxLineWidth;
+      break;
+   case 27:
+      glutDestroyWindow(Win);
+      exit(0);
+      break;
+   }
+   printf("Stipple: %d  Antialias: %d  LineWidth: %f\n",
+          Stipple, Anti, LineWidth);
+
+   glutPostRedisplay();
+}
+
+
+static void
+SpecialKey(int key, int x, int y)
+{
+   glutPostRedisplay();
+}
+
+
+static GLuint
+MakeFragmentShader(void)
+{
+   static const char *fragShaderText =
+      "uniform sampler2D stippleTex; \n"
+      "uniform vec2 viewportSize; \n"
+      "float scale = 1.0 / 16.0; \n"
+      "void main() \n"
+      "{ \n"
+      "   vec2 t = gl_FragCoord.xy * scale; \n"
+      "   gl_FragColor = gl_Color * texture2D(stippleTex, t); \n"
+      "} \n";
+
+   GLuint fragShader, program;
+   GLint stippleTex, viewportSize;
+
+   fragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
+   program = LinkShaders(0, fragShader);
+   glUseProgram(program);
+
+   stippleTex = glGetUniformLocation(program, "stippleTex");
+   glUniform1i(stippleTex, 0); /* unit 0 */
+
+   viewportSize = glGetUniformLocation(program, "viewportSize");
+   glUniform2f(viewportSize, WinWidth / 2.0, WinHeight);
+
+   glUseProgram(0);
+
+   return program;
+}
+
+
+static void
+Usage(void)
+{
+   printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
+   printf("Keys:\n");
+   printf("  a - toggle antialiasing\n");
+   printf("  s - toogle stippling\n");
+   printf("  w/W - decrease/increase line width\n");
+}
+
+
+static void
+Init(void)
+{
+   GLushort pattern = 0xf2;
+   GLuint tex;
+
+   if (!ShadersSupported())
+      exit(1);
+
+   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+   glLineStipple(1, pattern);
+
+   StippleProgram = MakeFragmentShader();
+
+   tex = LineStippleToTexture(pattern);
+   glBindTexture(GL_TEXTURE_2D, tex);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+   glutInit(&argc, argv);
+   glutInitWindowSize(WinWidth, WinHeight);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
+   Win = glutCreateWindow(argv[0]);
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutSpecialFunc(SpecialKey);
+   glutDisplayFunc(Draw);
+   glewInit();
+   Usage();
+   Init();
+   glutMainLoop();
+   return 0;
+}