demos: new glsl/array.c demo

Test variable indexing into a uniform array in a vertex shader.

diff --git a/progs/glsl/Makefile b/progs/glsl/Makefile
index 0f1a299570fab259d26f9abb0d75e5e6f8684dc1..5fb95c4b3bcd280427444e7ca6191ac998764ab7 100644 (file)
--- a/progs/glsl/Makefile
+++ b/progs/glsl/Makefile
@@ -10,6 +10,7 @@ LIB_DEP = $(TOP)/$(LIB_DIR)/$(GL_LIB_NAME) $(TOP)/$(LIB_DIR)/$(GLU_LIB_NAME) $(T
 LIBS = -L$(TOP)/$(LIB_DIR) -l$(GLUT_LIB) -l$(GLU_LIB) -l$(GL_LIB) $(APP_LIB_DEPS)
 
 PROGS = \
+       array \
        bitmap \
        brick \
        bump \
@@ -80,6 +81,13 @@ shaderutil.o: shaderutil.c shaderutil.h
 
 
 
+array.o: array.c extfuncs.h shaderutil.h
+       $(APP_CC) -c -I$(INCDIR) $(CFLAGS) array.c
+
+array: array.o shaderutil.o
+       $(APP_CC) -I$(INCDIR) $(CFLAGS) $(LDFLAGS) array.o shaderutil.o $(LIBS) -o $@
+
+
 bitmap.o: bitmap.c extfuncs.h shaderutil.h
        $(APP_CC) -c -I$(INCDIR) $(CFLAGS) bitmap.c
 

diff --git a/progs/glsl/array.c b/progs/glsl/array.c
new file mode 100644 (file)
index 0000000..46ef804
--- /dev/null
+++ b/progs/glsl/array.c
@@ -0,0 +1,261 @@
+/**
+ * Test variable array indexing in a vertex shader.
+ * Brian Paul
+ * 17 April 2009
+ */
+
+#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"
+
+
+/**
+ * The vertex position.z is used as a (variable) index into an
+ * array which returns a new Z value.
+ */
+static const char *VertShaderText =
+   "uniform sampler2D tex1; \n"
+   "uniform float HeightArray[20]; \n"
+   "void main() \n"
+   "{ \n"
+   "   vec4 pos = gl_Vertex; \n"
+   "   int i = int(pos.z * 9.5); \n"
+   "   pos.z = HeightArray[i]; \n"
+   "   gl_Position = gl_ModelViewProjectionMatrix * pos; \n"
+   "   gl_FrontColor = pos; \n"
+   "} \n";
+
+static const char *FragShaderText =
+   "void main() \n"
+   "{ \n"
+   "   gl_FragColor = gl_Color; \n"
+   "} \n";
+
+
+static GLuint fragShader;
+static GLuint vertShader;
+static GLuint program;
+
+static GLint win = 0;
+static GLboolean Anim = GL_TRUE;
+static GLboolean WireFrame = GL_TRUE;
+static GLfloat xRot = -70.0f, yRot = 0.0f, zRot = 0.0f;
+
+
+static void
+Idle(void)
+{
+   zRot = 90 + glutGet(GLUT_ELAPSED_TIME) * 0.05;
+   glutPostRedisplay();
+}
+
+
+/** z=f(x,y) */
+static float
+fz(float x, float y)
+{
+   return fabs(cos(1.5*x) + cos(1.5*y));
+}
+
+
+static void
+DrawMesh(void)
+{
+   GLfloat xmin = -2.0, xmax = 2.0;
+   GLfloat ymin = -2.0, ymax = 2.0;
+   GLuint xdivs = 20, ydivs = 20;
+   GLfloat dx = (xmax - xmin) / xdivs;
+   GLfloat dy = (ymax - ymin) / ydivs;
+   GLfloat ds = 1.0 / xdivs, dt = 1.0 / ydivs;
+   GLfloat x, y, s, t;
+   GLuint i, j;
+
+   y = ymin;
+   t = 0.0;
+   for (i = 0; i < ydivs; i++) {
+      x = xmin;
+      s = 0.0;
+      glBegin(GL_QUAD_STRIP);
+      for (j = 0; j < xdivs; j++) {
+         float z0 = fz(x, y), z1 = fz(x, y + dy);
+
+         glTexCoord2f(s, t);
+         glVertex3f(x, y, z0);
+
+         glTexCoord2f(s, t + dt);
+         glVertex3f(x, y + dy, z1);
+         x += dx;
+         s += ds;
+      }
+      glEnd();
+      y += dy;
+      t += dt;
+   }
+}
+
+
+static void
+Redisplay(void)
+{
+   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+   
+   if (WireFrame)
+      glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+   else
+      glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+
+   glPushMatrix();
+   glRotatef(xRot, 1.0f, 0.0f, 0.0f);
+   glRotatef(yRot, 0.0f, 1.0f, 0.0f);
+   glRotatef(zRot, 0.0f, 0.0f, 1.0f);
+
+   glPushMatrix();
+   DrawMesh();
+   glPopMatrix();
+
+   glPopMatrix();
+
+   glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+
+   glutSwapBuffers();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+   glViewport(0, 0, width, height);
+   glMatrixMode(GL_PROJECTION);
+   glLoadIdentity();
+   glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
+   glMatrixMode(GL_MODELVIEW);
+   glLoadIdentity();
+   glTranslatef(0.0f, 0.0f, -15.0f);
+}
+
+
+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)
+{
+   const GLfloat step = 2.0;
+   (void) x;
+   (void) y;
+
+   switch(key) {
+   case 'a':
+      Anim = !Anim;
+      if (Anim)
+         glutIdleFunc(Idle);
+      else
+         glutIdleFunc(NULL);
+      break;
+   case 'w':
+      WireFrame = !WireFrame;
+      break;
+   case 'z':
+      zRot += step;
+      break;
+   case 'Z':
+      zRot -= step;
+      break;
+   case 27:
+      CleanUp();
+      exit(0);
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+SpecialKey(int key, int x, int y)
+{
+   const GLfloat step = 2.0;
+
+   (void) x;
+   (void) y;
+
+   switch(key) {
+   case GLUT_KEY_UP:
+      xRot += step;
+      break;
+   case GLUT_KEY_DOWN:
+      xRot -= step;
+      break;
+   case GLUT_KEY_LEFT:
+      yRot -= step;
+      break;
+   case GLUT_KEY_RIGHT:
+      yRot += step;
+      break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+Init(void)
+{
+   GLfloat HeightArray[20];
+   GLint u, i;
+
+   if (!ShadersSupported())
+      exit(1);
+
+   GetExtensionFuncs();
+
+   vertShader = CompileShaderText(GL_VERTEX_SHADER, VertShaderText);
+   fragShader = CompileShaderText(GL_FRAGMENT_SHADER, FragShaderText);
+   program = LinkShaders(vertShader, fragShader);
+
+   glUseProgram_func(program);
+
+   /* Setup the HeightArray[] uniform */
+   for (i = 0; i < 20; i++)
+      HeightArray[i] = i / 20.0;
+   u = glGetUniformLocation_func(program, "HeightArray");
+   glUniform1fv_func(u, 20, HeightArray);
+
+   assert(glGetError() == 0);
+
+   glClearColor(0.4f, 0.4f, 0.8f, 0.0f);
+   glEnable(GL_DEPTH_TEST);
+   glColor3f(1, 1, 1);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+   glutInit(&argc, argv);
+   glutInitWindowSize(500, 500);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
+   win = glutCreateWindow(argv[0]);
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutSpecialFunc(SpecialKey);
+   glutDisplayFunc(Redisplay);
+   Init();
+   if (Anim)
+      glutIdleFunc(Idle);
+   glutMainLoop();
+   return 0;
+}
+