/** * 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/glew.h> #include <GL/glut.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(fragShader); glDeleteShader(vertShader); glDeleteProgram(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); vertShader = CompileShaderText(GL_VERTEX_SHADER, VertShaderText); fragShader = CompileShaderText(GL_FRAGMENT_SHADER, FragShaderText); program = LinkShaders(vertShader, fragShader); glUseProgram(program); /* Setup the HeightArray[] uniform */ for (i = 0; i < 20; i++) HeightArray[i] = i / 20.0; u = glGetUniformLocation(program, "HeightArray"); glUniform1fv(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]); glewInit(); glutReshapeFunc(Reshape); glutKeyboardFunc(Key); glutSpecialFunc(SpecialKey); glutDisplayFunc(Redisplay); Init(); if (Anim) glutIdleFunc(Idle); glutMainLoop(); return 0; }