Demos (master): geom-stipple-lines: do line stipple with geometry/ fragment shaders
Brian Paul
brianp at kemper.freedesktop.org
Mon Apr 18 17:55:09 UTC 2011
Module: Demos
Branch: master
Commit: 466f360ecdc5ec07da9c9def02cbc7a0f355f60d
URL: http://cgit.freedesktop.org/mesa/demos/commit/?id=466f360ecdc5ec07da9c9def02cbc7a0f355f60d
Author: Brian Paul <brianp at vmware.com>
Date: Mon Apr 18 11:46:51 2011 -0600
geom-stipple-lines: do line stipple with geometry/fragment shaders
---
src/glsl/CMakeLists.txt | 1 +
src/glsl/Makefile.am | 2 +
src/glsl/geom-stipple-lines.c | 324 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 327 insertions(+), 0 deletions(-)
diff --git a/src/glsl/CMakeLists.txt b/src/glsl/CMakeLists.txt
index 63b4801..ef2f1ba 100644
--- a/src/glsl/CMakeLists.txt
+++ b/src/glsl/CMakeLists.txt
@@ -29,6 +29,7 @@ set (targets
fragcoord
fsraytrace
geom-sprites
+ geom-stipple-lines
geom-wide-lines
identity
linktest
diff --git a/src/glsl/Makefile.am b/src/glsl/Makefile.am
index 7f96a5c..5a9a802 100644
--- a/src/glsl/Makefile.am
+++ b/src/glsl/Makefile.am
@@ -42,6 +42,7 @@ bin_PROGRAMS = \
fragcoord \
fsraytrace \
geom-sprites \
+ geom-stipple-lines \
geom-wide-lines \
identity \
linktest \
@@ -79,6 +80,7 @@ bump_LDADD = ../util/libutil.la
convolutions_LDADD = ../util/libutil.la
deriv_LDADD = ../util/libutil.la
geom_sprites_LDADD = ../util/libutil.la
+geom_stipple_lines_LDADD = ../util/libutil.la
geom_wide_lines_LDADD = ../util/libutil.la
fsraytrace_LDADD = ../util/libutil.la
fragcoord_LDADD = ../util/libutil.la
diff --git a/src/glsl/geom-stipple-lines.c b/src/glsl/geom-stipple-lines.c
new file mode 100644
index 0000000..3c7c97a
--- /dev/null
+++ b/src/glsl/geom-stipple-lines.c
@@ -0,0 +1,324 @@
+/**
+ * Test using a geometry and fragment shaders to implement stippled lines.
+ *
+ * Brian Paul
+ * April 2011
+ */
+
+#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 GLint WinWidth = 500, WinHeight = 500;
+static GLint Win = 0;
+static GLuint VertShader, GeomShader, FragShader, Program;
+static GLboolean Anim = GL_TRUE;
+static GLboolean UseGeomShader = GL_TRUE;
+static GLfloat Xrot = 0, Yrot = 0;
+static int uViewportSize = -1, uStippleTex = -1, uStippleFactor;
+static const int NumPoints = 50;
+static float Points[100][3], Colors[100][3];
+
+static const GLushort StipplePattern = 0x10ff;
+static GLuint StippleFactor = 2;
+
+
+static void
+CheckError(int line)
+{
+ GLenum err = glGetError();
+ if (err) {
+ printf("GL Error %s (0x%x) at line %d\n",
+ gluErrorString(err), (int) err, line);
+ }
+}
+
+
+static GLuint
+MakeStippleTexture(GLushort pattern)
+{
+ GLuint tex, i;
+ GLubyte image[16];
+
+ for (i = 0; i < 16; i++) {
+ image[i] = (pattern & (1 << i)) ? 0xff : 0;
+ }
+
+ glGenTextures(1, &tex);
+ glBindTexture(GL_TEXTURE_1D, tex);
+ glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+ glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+ glTexImage1D(GL_TEXTURE_1D, 0, GL_LUMINANCE, 16, 0,
+ GL_LUMINANCE, GL_UNSIGNED_BYTE, image);
+
+ return tex;
+}
+
+
+static void
+Redisplay(void)
+{
+ int i;
+
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
+
+ glPushMatrix();
+ glRotatef(Xrot, 1, 0, 0);
+ glRotatef(Yrot, 0, 0, 1);
+
+ if (UseGeomShader) {
+ glUseProgram(Program);
+ glDisable(GL_LINE_STIPPLE);
+ }
+ else {
+ glUseProgram(0);
+ glEnable(GL_LINE_STIPPLE);
+ }
+
+ glBegin(GL_LINES);
+ for (i = 0; i < NumPoints; i++) {
+ glColor3fv(Colors[i]);
+ glVertex3fv(Points[i]);
+ }
+ glEnd();
+
+ glPopMatrix();
+
+ glutSwapBuffers();
+}
+
+
+static void
+Idle(void)
+{
+ int curTime = glutGet(GLUT_ELAPSED_TIME);
+ Xrot = curTime * 0.02;
+ Yrot = curTime * 0.05;
+ glutPostRedisplay();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+ float ar = (float) width / height;
+ glViewport(0, 0, width, height);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+#if 1
+ glFrustum(-ar, ar, -1, 1, 3, 25);
+#else
+ glOrtho(-3.0*ar, 3.0*ar, -3.0, 3.0, 3, 25);
+#endif
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+ glTranslatef(0, 0, -10);
+
+ {
+ GLfloat viewport[4];
+ glGetFloatv(GL_VIEWPORT, viewport);
+ glUniform2f(uViewportSize, viewport[2], viewport[3]);
+ }
+}
+
+
+static void
+CleanUp(void)
+{
+ glDeleteShader(FragShader);
+ glDeleteShader(VertShader);
+ glDeleteShader(GeomShader);
+ glDeleteProgram(Program);
+ glutDestroyWindow(Win);
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+ (void) x;
+ (void) y;
+
+ switch(key) {
+ case ' ':
+ case 'a':
+ Anim = !Anim;
+ if (Anim) {
+ glutIdleFunc(Idle);
+ }
+ else
+ glutIdleFunc(NULL);
+ break;
+ case 'g':
+ UseGeomShader = !UseGeomShader;
+ printf("Use geometry shader? %d\n", UseGeomShader);
+ break;
+ case 'x':
+ Xrot ++;
+ break;
+ case 27:
+ CleanUp();
+ exit(0);
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void
+MakePoints(void)
+{
+ int i;
+ for (i = 0; i < NumPoints; i++) {
+ Colors[i][0] = (rand() % 1000) / 1000.0;
+ Colors[i][1] = (rand() % 1000) / 1000.0;
+ Colors[i][2] = (rand() % 1000) / 1000.0;
+ Points[i][0] = ((rand() % 2000) - 1000.0) / 500.0;
+ Points[i][1] = ((rand() % 2000) - 1000.0) / 500.0;
+ Points[i][2] = ((rand() % 2000) - 1000.0) / 500.0;
+ }
+}
+
+
+static void
+Init(void)
+{
+ GLuint tex;
+
+ static const char *fragShaderText =
+ "uniform sampler1D StippleTex; \n"
+ "varying float stippleCoord; \n"
+ "void main() \n"
+ "{ \n"
+ " // sample the stipple pattern and discard if value is zero \n"
+ " // TODO: we should really undo the perspective interpolation here \n"
+ " // so that it's linear. \n"
+ " vec4 stip = texture1D(StippleTex, stippleCoord); \n"
+ " if (stip.x == 0.0) \n"
+ " discard; \n"
+ " gl_FragColor = gl_Color; \n"
+ "} \n";
+ static const char *vertShaderText =
+ "void main() \n"
+ "{ \n"
+ " gl_FrontColor = gl_Color; \n"
+ " gl_Position = ftransform(); \n"
+ "} \n";
+ static const char *geomShaderText =
+ "#version 120 \n"
+ "#extension GL_ARB_geometry_shader4: enable \n"
+ "uniform vec2 ViewportSize; \n"
+ "uniform float StippleFactor; \n"
+ "varying float stippleCoord; \n"
+ "void main() \n"
+ "{ \n"
+ " vec4 pos0 = gl_PositionIn[0]; \n"
+ " vec4 pos1 = gl_PositionIn[1]; \n"
+ " // Convert eye coords to window coords \n"
+ " // Note: we're off by a factor of two here, make up for that below \n"
+ " vec2 p0 = pos0.xy / pos0.w * ViewportSize; \n"
+ " vec2 p1 = pos1.xy / pos1.w * ViewportSize; \n"
+ " float len = length(p0.xy - p1.xy); \n"
+ " len /= StippleFactor; \n"
+ " // Emit first vertex \n"
+ " gl_FrontColor = gl_FrontColorIn[0]; \n"
+ " gl_Position = pos0; \n"
+ " stippleCoord = 0.0; \n"
+ " EmitVertex(); \n"
+ " // Emit second vertex \n"
+ " gl_FrontColor = gl_FrontColorIn[1]; \n"
+ " gl_Position = pos1; \n"
+ " stippleCoord = len / 32.0; // Note: not 16, see above \n"
+ " EmitVertex(); \n"
+ "} \n";
+
+ if (!ShadersSupported())
+ exit(1);
+
+ if (!glutExtensionSupported("GL_ARB_geometry_shader4")) {
+ fprintf(stderr, "Sorry, GL_ARB_geometry_shader4 is not supported.\n");
+ exit(1);
+ }
+
+ VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
+ FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
+ GeomShader = CompileShaderText(GL_GEOMETRY_SHADER_ARB, geomShaderText);
+ assert(GeomShader);
+
+ Program = LinkShaders3(VertShader, GeomShader, FragShader);
+ assert(Program);
+ CheckError(__LINE__);
+
+ /*
+ * The geometry shader accepts lines and produces lines.
+ */
+ glProgramParameteriARB(Program, GL_GEOMETRY_INPUT_TYPE_ARB,
+ GL_LINES);
+ glProgramParameteriARB(Program, GL_GEOMETRY_OUTPUT_TYPE_ARB,
+ GL_LINE_STRIP);
+ glProgramParameteriARB(Program, GL_GEOMETRY_VERTICES_OUT_ARB, 4);
+ CheckError(__LINE__);
+
+ glLinkProgramARB(Program);
+
+ /* check link */
+ {
+ GLint stat;
+ GetProgramiv(Program, GL_LINK_STATUS, &stat);
+ if (!stat) {
+ GLchar log[1000];
+ GLsizei len;
+ GetProgramInfoLog(Program, 1000, &len, log);
+ fprintf(stderr, "Shader link error:\n%s\n", log);
+ }
+ }
+
+ glUseProgram(Program);
+
+ uViewportSize = glGetUniformLocation(Program, "ViewportSize");
+ uStippleTex = glGetUniformLocation(Program, "StippleTex");
+ uStippleFactor = glGetUniformLocation(Program, "StippleFactor");
+
+ glUniform1i(uStippleTex, 0); /* texture unit 0 */
+ glUniform1f(uStippleFactor, StippleFactor);
+
+ glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
+
+ printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
+
+ assert(glIsProgram(Program));
+ assert(glIsShader(FragShader));
+ assert(glIsShader(VertShader));
+ assert(glIsShader(GeomShader));
+
+
+ glLineStipple(StippleFactor, StipplePattern);
+ tex = MakeStippleTexture(StipplePattern);
+
+ MakePoints();
+}
+
+
+int
+main(int argc, char *argv[])
+{
+ glutInit(&argc, argv);
+ glutInitWindowSize(WinWidth, WinHeight);
+ glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
+ Win = glutCreateWindow(argv[0]);
+ glewInit();
+ glutReshapeFunc(Reshape);
+ glutKeyboardFunc(Key);
+ glutDisplayFunc(Redisplay);
+ if (Anim)
+ glutIdleFunc(Idle);
+
+ Init();
+ glutMainLoop();
+ return 0;
+}
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